| // Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| import 'package:meta/meta.dart'; |
| |
| /// [AssignedVariables] is a helper class capable of computing the set of |
| /// variables that are potentially written to, and potentially captured by |
| /// closures, at various locations inside the code being analyzed. This class |
| /// should be used prior to running flow analysis, to compute the sets of |
| /// variables to pass in to flow analysis. |
| /// |
| /// This class is intended to be used in two phases. In the first phase, the |
| /// client should traverse the source code recursively, making calls to |
| /// [beginNode] and [endNode] to indicate the constructs in which writes should |
| /// be tracked, and calls to [write] to indicate when a write is encountered. |
| /// The order of visiting is not important provided that nesting is respected. |
| /// This phase is called the "pre-traversal" because it should happen prior to |
| /// flow analysis. |
| /// |
| /// Then, in the second phase, the client may make queries using |
| /// [capturedAnywhere], [writtenInNode], and [capturedInNode]. |
| /// |
| /// We use the term "node" to refer generally to a loop statement, switch |
| /// statement, try statement, loop collection element, local function, or |
| /// closure. |
| class AssignedVariables<Node, Variable> { |
| /// Mapping from a node to the info for that node. |
| final Map<Node, AssignedVariablesNodeInfo<Variable>> _info = |
| new Map<Node, AssignedVariablesNodeInfo<Variable>>.identity(); |
| |
| /// Info for the variables written or captured anywhere in the code being |
| /// analyzed. |
| final AssignedVariablesNodeInfo<Variable> _anywhere = |
| new AssignedVariablesNodeInfo<Variable>(); |
| |
| /// Stack of info for nodes that have been entered but not yet left. |
| final List<AssignedVariablesNodeInfo<Variable>> _stack = [ |
| new AssignedVariablesNodeInfo<Variable>() |
| ]; |
| |
| /// When assertions are enabled, the set of info objects that have been |
| /// retrieved by [deferNode] but not yet sent to [storeNode]. |
| final Set<AssignedVariablesNodeInfo<Variable>> _deferredInfos = |
| new Set<AssignedVariablesNodeInfo<Variable>>.identity(); |
| |
| /// This method should be called during pre-traversal, to mark the start of a |
| /// loop statement, switch statement, try statement, loop collection element, |
| /// local function, or closure which might need to be queried later. |
| /// |
| /// [isClosure] should be true if the node is a local function or closure. |
| /// |
| /// The span between the call to [beginNode] and [endNode] should cover any |
| /// statements and expressions that might be crossed by a backwards jump. So |
| /// for instance, in a "for" loop, the condition, updaters, and body should be |
| /// covered, but the initializers should not. Similarly, in a switch |
| /// statement, the body of the switch statement should be covered, but the |
| /// switch expression should not. |
| void beginNode() { |
| _stack.add(new AssignedVariablesNodeInfo<Variable>()); |
| } |
| |
| /// This method should be called during pre-traversal, to indicate that the |
| /// declaration of a variable has been found. |
| /// |
| /// It is not required for the declaration to be seen prior to its use (this |
| /// is to allow for error recovery in the analyzer). |
| void declare(Variable variable) { |
| _stack.last._declared.add(variable); |
| } |
| |
| /// This method may be called during pre-traversal, to mark the end of a |
| /// loop statement, switch statement, try statement, loop collection element, |
| /// local function, or closure which might need to be queried later. |
| /// |
| /// [isClosure] should be true if the node is a local function or closure. |
| /// |
| /// In contrast to [endNode], this method doesn't store the data gathered for |
| /// the node for later use; instead it returns it to the caller. At a later |
| /// time, the caller should pass the returned data to [storeNodeInfo]. |
| /// |
| /// See [beginNode] for more details. |
| AssignedVariablesNodeInfo<Variable> deferNode({bool isClosure: false}) { |
| AssignedVariablesNodeInfo<Variable> info = _stack.removeLast(); |
| info._written.removeAll(info._declared); |
| info._captured.removeAll(info._declared); |
| AssignedVariablesNodeInfo<Variable> last = _stack.last; |
| last._written.addAll(info._written); |
| last._captured.addAll(info._captured); |
| if (isClosure) { |
| last._captured.addAll(info._written); |
| _anywhere._captured.addAll(info._written); |
| } |
| // If we have already deferred this info, something has gone horribly wrong. |
| assert(_deferredInfos.add(info)); |
| return info; |
| } |
| |
| /// This method may be called during pre-traversal, to discard the effects of |
| /// the most recent unmatched call to [beginNode]. |
| /// |
| /// This is necessary because try/catch/finally needs to be desugared into |
| /// a try/catch nested inside a try/finally, however the pre-traversal phase |
| /// of the front end happens during parsing, so when a `try` is encountered, |
| /// it is not known whether it will need to be desugared into two nested |
| /// `try`s. To cope with this, the front end may call [beginNode] twice upon |
| /// seeing the two `try`s, and later if it turns out that no desugaring was |
| /// needed, use [discardNode] to discard the effects of one of the [beginNode] |
| /// calls. |
| void discardNode() { |
| AssignedVariablesNodeInfo<Variable> discarded = _stack.removeLast(); |
| AssignedVariablesNodeInfo<Variable> last = _stack.last; |
| last._declared.addAll(discarded._declared); |
| last._written.addAll(discarded._written); |
| last._captured.addAll(discarded._captured); |
| } |
| |
| /// This method should be called during pre-traversal, to mark the end of a |
| /// loop statement, switch statement, try statement, loop collection element, |
| /// local function, or closure which might need to be queried later. |
| /// |
| /// [isClosure] should be true if the node is a local function or closure. |
| /// |
| /// This is equivalent to a call to [deferNode] followed immediately by a call |
| /// to [storeInfo]. |
| /// |
| /// See [beginNode] for more details. |
| void endNode(Node node, {bool isClosure: false}) { |
| storeInfo(node, deferNode(isClosure: isClosure)); |
| } |
| |
| /// Call this after visiting the code to be analyzed, to check invariants. |
| void finish() { |
| assert(() { |
| assert( |
| _deferredInfos.isEmpty, "Deferred infos not stored: $_deferredInfos"); |
| assert(_stack.length == 1, "Unexpected stack: $_stack"); |
| AssignedVariablesNodeInfo<Variable> last = _stack.last; |
| Set<Variable> undeclaredWrites = last._written.difference(last._declared); |
| assert(undeclaredWrites.isEmpty, |
| 'Variables written to but not declared: $undeclaredWrites'); |
| Set<Variable> undeclaredCaptures = |
| last._captured.difference(last._declared); |
| assert(undeclaredCaptures.isEmpty, |
| 'Variables captured but not declared: $undeclaredCaptures'); |
| return true; |
| }()); |
| } |
| |
| /// Call this method to register that the node [from] for which information |
| /// has been stored is replaced by the node [to]. |
| // TODO(johnniwinther): Remove this when unified collections are encoded as |
| // general elements in the front-end. |
| void reassignInfo(Node from, Node to) { |
| assert(!_info.containsKey(to), "Node $to already has info: ${_info[to]}"); |
| AssignedVariablesNodeInfo<Variable> info = _info.remove(from); |
| assert( |
| info != null, |
| 'No information for $from (${from.hashCode}) in ' |
| '{${_info.keys.map((k) => '$k (${k.hashCode})').join(',')}}'); |
| |
| _info[to] = info; |
| } |
| |
| /// This method may be called at any time between a call to [deferNode] and |
| /// the call to [finish], to store assigned variable info for the node. |
| void storeInfo(Node node, AssignedVariablesNodeInfo<Variable> info) { |
| // Caller should not try to store the same piece of info more than once. |
| assert(_deferredInfos.remove(info)); |
| _info[node] = info; |
| } |
| |
| String toString() { |
| StringBuffer sb = new StringBuffer(); |
| sb.write('AssignedVariables('); |
| _printOn(sb); |
| sb.write(')'); |
| return sb.toString(); |
| } |
| |
| /// This method should be called during pre-traversal, to mark a write to a |
| /// variable. |
| void write(Variable variable) { |
| _stack.last._written.add(variable); |
| _anywhere._written.add(variable); |
| } |
| |
| /// Queries the information stored for the given [node]. |
| AssignedVariablesNodeInfo<Variable> _getInfoForNode(Node node) { |
| return _info[node] ?? |
| (throw new StateError('No information for $node (${node.hashCode}) in ' |
| '{${_info.keys.map((k) => '$k (${k.hashCode})').join(',')}}')); |
| } |
| |
| void _printOn(StringBuffer sb) { |
| sb.write('_info=$_info,'); |
| sb.write('_stack=$_stack,'); |
| sb.write('_anywhere=$_anywhere'); |
| } |
| } |
| |
| /// Extension of [AssignedVariables] intended for use in tests. This class |
| /// exposes the results of the analysis so that they can be tested directly. |
| /// Not intended to be used by clients of flow analysis. |
| class AssignedVariablesForTesting<Node, Variable> |
| extends AssignedVariables<Node, Variable> { |
| Set<Variable> get capturedAnywhere => _anywhere._captured; |
| |
| Set<Variable> get declaredAtTopLevel => _stack.first._declared; |
| |
| Set<Variable> get writtenAnywhere => _anywhere._written; |
| |
| Set<Variable> capturedInNode(Node node) => _getInfoForNode(node)._captured; |
| |
| Set<Variable> declaredInNode(Node node) => _getInfoForNode(node)._declared; |
| |
| bool isTracked(Node node) => _info.containsKey(node); |
| |
| String toString() { |
| StringBuffer sb = new StringBuffer(); |
| sb.write('AssignedVariablesForTesting('); |
| _printOn(sb); |
| sb.write(')'); |
| return sb.toString(); |
| } |
| |
| Set<Variable> writtenInNode(Node node) => _getInfoForNode(node)._written; |
| } |
| |
| /// Information tracked by [AssignedVariables] for a single node. |
| class AssignedVariablesNodeInfo<Variable> { |
| /// The set of local variables that are potentially written in the node. |
| final Set<Variable> _written = new Set<Variable>.identity(); |
| |
| /// The set of local variables for which a potential write is captured by a |
| /// local function or closure inside the node. |
| final Set<Variable> _captured = new Set<Variable>.identity(); |
| |
| /// The set of local variables that are declared in the node. |
| final Set<Variable> _declared = new Set<Variable>.identity(); |
| |
| String toString() => |
| 'AssignedVariablesNodeInfo(_written=$_written, _captured=$_captured, ' |
| '_declared=$_declared)'; |
| } |
| |
| /// A collection of flow models representing the possible outcomes of evaluating |
| /// an expression that are relevant to flow analysis. |
| class ExpressionInfo<Variable, Type> { |
| /// The state after the expression evaluates, if we don't care what it |
| /// evaluates to. |
| final FlowModel<Variable, Type> after; |
| |
| /// The state after the expression evaluates, if it evaluates to `true`. |
| final FlowModel<Variable, Type> ifTrue; |
| |
| /// The state after the expression evaluates, if it evaluates to `false`. |
| final FlowModel<Variable, Type> ifFalse; |
| |
| ExpressionInfo(this.after, this.ifTrue, this.ifFalse); |
| |
| @override |
| String toString() => |
| 'ExpressionInfo(after: $after, _ifTrue: $ifTrue, ifFalse: $ifFalse)'; |
| |
| /// Compute a new [ExpressionInfo] based on this one, but with the roles of |
| /// [ifTrue] and [ifFalse] reversed. |
| static ExpressionInfo<Variable, Type> invert<Variable, Type>( |
| ExpressionInfo<Variable, Type> info) => |
| new ExpressionInfo<Variable, Type>(info.after, info.ifFalse, info.ifTrue); |
| } |
| |
| /// Implementation of flow analysis to be shared between the analyzer and the |
| /// front end. |
| /// |
| /// The client should create one instance of this class for every method, field, |
| /// or top level variable to be analyzed, and call the appropriate methods |
| /// while visiting the code for type inference. |
| abstract class FlowAnalysis<Node, Statement extends Node, Expression, Variable, |
| Type> { |
| factory FlowAnalysis(TypeOperations<Variable, Type> typeOperations, |
| AssignedVariables<Node, Variable> assignedVariables) { |
| return new _FlowAnalysisImpl(typeOperations, assignedVariables); |
| } |
| |
| /// Return `true` if the current state is reachable. |
| bool get isReachable; |
| |
| /// Call this method after visiting an "as" expression. |
| /// |
| /// [subExpression] should be the expression to which the "as" check was |
| /// applied. [type] should be the type being checked. |
| void asExpression_end(Expression subExpression, Type type); |
| |
| /// Call this method after visiting the condition part of an assert statement |
| /// (or assert initializer). |
| /// |
| /// [condition] should be the assert statement's condition. |
| /// |
| /// See [assert_begin] for more information. |
| void assert_afterCondition(Expression condition); |
| |
| /// Call this method before visiting the condition part of an assert statement |
| /// (or assert initializer). |
| /// |
| /// The order of visiting an assert statement with no "message" part should |
| /// be: |
| /// - Call [assert_begin] |
| /// - Visit the condition |
| /// - Call [assert_afterCondition] |
| /// - Call [assert_end] |
| /// |
| /// The order of visiting an assert statement with a "message" part should be: |
| /// - Call [assert_begin] |
| /// - Visit the condition |
| /// - Call [assert_afterCondition] |
| /// - Visit the message |
| /// - Call [assert_end] |
| void assert_begin(); |
| |
| /// Call this method after visiting an assert statement (or assert |
| /// initializer). |
| /// |
| /// See [assert_begin] for more information. |
| void assert_end(); |
| |
| /// Call this method when visiting a boolean literal expression. |
| void booleanLiteral(Expression expression, bool value); |
| |
| /// Call this method upon reaching the ":" part of a conditional expression |
| /// ("?:"). [thenExpression] should be the expression preceding the ":". |
| void conditional_elseBegin(Expression thenExpression); |
| |
| /// Call this method when finishing the visit of a conditional expression |
| /// ("?:"). [elseExpression] should be the expression preceding the ":", and |
| /// [conditionalExpression] should be the whole conditional expression. |
| void conditional_end( |
| Expression conditionalExpression, Expression elseExpression); |
| |
| /// Call this method upon reaching the "?" part of a conditional expression |
| /// ("?:"). [condition] should be the expression preceding the "?". |
| void conditional_thenBegin(Expression condition); |
| |
| /// Register a declaration of the [variable] in the current state. |
| /// Should also be called for function parameters. |
| /// |
| /// A local variable is [initialized] if its declaration has an initializer. |
| /// A function parameter is always initialized, so [initialized] is `true`. |
| void declare(Variable variable, bool initialized); |
| |
| /// Call this method before visiting the body of a "do-while" statement. |
| /// [doStatement] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the do-while statement. |
| void doStatement_bodyBegin(Statement doStatement); |
| |
| /// Call this method after visiting the body of a "do-while" statement, and |
| /// before visiting its condition. |
| void doStatement_conditionBegin(); |
| |
| /// Call this method after visiting the condition of a "do-while" statement. |
| /// [condition] should be the condition of the loop. |
| void doStatement_end(Expression condition); |
| |
| /// Call this method just after visiting a binary `==` or `!=` expression. |
| void equalityOp_end(Expression wholeExpression, Expression rightOperand, |
| {bool notEqual = false}); |
| |
| /// Call this method just after visiting the left hand side of a binary `==` |
| /// or `!=` expression. |
| void equalityOp_rightBegin(Expression leftOperand); |
| |
| /// This method should be called at the conclusion of flow analysis for a top |
| /// level function or method. Performs assertion checks. |
| void finish(); |
| |
| /// Call this method just before visiting the body of a conventional "for" |
| /// statement or collection element. See [for_conditionBegin] for details. |
| /// |
| /// If a "for" statement is being entered, [node] is an opaque representation |
| /// of the loop, for use as the target of future calls to [handleBreak] or |
| /// [handleContinue]. If a "for" collection element is being entered, [node] |
| /// should be `null`. |
| /// |
| /// [condition] is an opaque representation of the loop condition; it is |
| /// matched against expressions passed to previous calls to determine whether |
| /// the loop condition should cause any promotions to occur. If [condition] |
| /// is null, the condition is understood to be empty (equivalent to a |
| /// condition of `true`). |
| void for_bodyBegin(Statement node, Expression condition); |
| |
| /// Call this method just before visiting the condition of a conventional |
| /// "for" statement or collection element. |
| /// |
| /// Note that a conventional "for" statement is a statement of the form |
| /// `for (initializers; condition; updaters) body`. Statements of the form |
| /// `for (variable in iterable) body` should use [forEach_bodyBegin]. Similar |
| /// for "for" collection elements. |
| /// |
| /// The order of visiting a "for" statement or collection element should be: |
| /// - Visit the initializers. |
| /// - Call [for_conditionBegin]. |
| /// - Visit the condition. |
| /// - Call [for_bodyBegin]. |
| /// - Visit the body. |
| /// - Call [for_updaterBegin]. |
| /// - Visit the updaters. |
| /// - Call [for_end]. |
| /// |
| /// [node] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the for statement. |
| void for_conditionBegin(Node node); |
| |
| /// Call this method just after visiting the updaters of a conventional "for" |
| /// statement or collection element. See [for_conditionBegin] for details. |
| void for_end(); |
| |
| /// Call this method just before visiting the updaters of a conventional "for" |
| /// statement or collection element. See [for_conditionBegin] for details. |
| void for_updaterBegin(); |
| |
| /// Call this method just before visiting the body of a "for-in" statement or |
| /// collection element. |
| /// |
| /// The order of visiting a "for-in" statement or collection element should |
| /// be: |
| /// - Visit the iterable expression. |
| /// - Call [forEach_bodyBegin]. |
| /// - Visit the body. |
| /// - Call [forEach_end]. |
| /// |
| /// [node] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the for statement. [loopVariable] should |
| /// be the variable assigned to by the loop (if it is promotable, otherwise |
| /// null). [writtenType] should be the type written to that variable (i.e. |
| /// if the loop iterates over `List<Foo>`, it should be `Foo`). |
| void forEach_bodyBegin(Node node, Variable loopVariable, Type writtenType); |
| |
| /// Call this method just before visiting the body of a "for-in" statement or |
| /// collection element. See [forEach_bodyBegin] for details. |
| void forEach_end(); |
| |
| /// Call this method just before visiting the body of a function expression or |
| /// local function. |
| /// |
| /// [node] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the function expression. |
| void functionExpression_begin(Node node); |
| |
| /// Call this method just after visiting the body of a function expression or |
| /// local function. |
| void functionExpression_end(); |
| |
| /// Call this method when visiting a break statement. [target] should be the |
| /// statement targeted by the break. |
| void handleBreak(Statement target); |
| |
| /// Call this method when visiting a continue statement. [target] should be |
| /// the statement targeted by the continue. |
| void handleContinue(Statement target); |
| |
| /// Register the fact that the current state definitely exists, e.g. returns |
| /// from the body, throws an exception, etc. |
| /// |
| /// Should also be called if a subexpression's type is Never. |
| void handleExit(); |
| |
| /// Call this method after visiting the RHS of an if-null expression ("??") |
| /// or if-null assignment ("??="). |
| /// |
| /// Note: for an if-null assignment, the call to [write] should occur before |
| /// the call to [ifNullExpression_end] (since the write only occurs if the |
| /// read resulted in a null value). |
| void ifNullExpression_end(); |
| |
| /// Call this method after visiting the LHS of an if-null expression ("??") |
| /// or if-null assignment ("??="). |
| void ifNullExpression_rightBegin(Expression leftHandSide); |
| |
| /// Call this method after visiting the "then" part of an if statement, and |
| /// before visiting the "else" part. |
| void ifStatement_elseBegin(); |
| |
| /// Call this method after visiting an if statement. |
| void ifStatement_end(bool hasElse); |
| |
| /// Call this method after visiting the condition part of an if statement. |
| /// [condition] should be the if statement's condition. |
| /// |
| /// The order of visiting an if statement with no "else" part should be: |
| /// - Visit the condition |
| /// - Call [ifStatement_thenBegin] |
| /// - Visit the "then" statement |
| /// - Call [ifStatement_end], passing `false` for `hasElse`. |
| /// |
| /// The order of visiting an if statement with an "else" part should be: |
| /// - Visit the condition |
| /// - Call [ifStatement_thenBegin] |
| /// - Visit the "then" statement |
| /// - Call [ifStatement_elseBegin] |
| /// - Visit the "else" statement |
| /// - Call [ifStatement_end], passing `true` for `hasElse`. |
| void ifStatement_thenBegin(Expression condition); |
| |
| /// Return whether the [variable] is definitely assigned in the current state. |
| bool isAssigned(Variable variable); |
| |
| /// Call this method after visiting the LHS of an "is" expression. |
| /// |
| /// [isExpression] should be the complete expression. [subExpression] should |
| /// be the expression to which the "is" check was applied. [isNot] should be |
| /// a boolean indicating whether this is an "is" or an "is!" expression. |
| /// [type] should be the type being checked. |
| void isExpression_end( |
| Expression isExpression, Expression subExpression, bool isNot, Type type); |
| |
| /// Return whether the [variable] is definitely unassigned in the current |
| /// state. |
| bool isUnassigned(Variable variable); |
| |
| /// Call this method before visiting a labeled statement. |
| /// Call [labeledStatement_end] after visiting the statement. |
| void labeledStatement_begin(Node node); |
| |
| /// Call this method after visiting a labeled statement. |
| void labeledStatement_end(); |
| |
| /// Call this method after visiting the RHS of a logical binary operation |
| /// ("||" or "&&"). |
| /// [wholeExpression] should be the whole logical binary expression. |
| /// [rightOperand] should be the RHS. [isAnd] should indicate whether the |
| /// logical operator is "&&" or "||". |
| void logicalBinaryOp_end(Expression wholeExpression, Expression rightOperand, |
| {@required bool isAnd}); |
| |
| /// Call this method after visiting the LHS of a logical binary operation |
| /// ("||" or "&&"). |
| /// [rightOperand] should be the LHS. [isAnd] should indicate whether the |
| /// logical operator is "&&" or "||". |
| void logicalBinaryOp_rightBegin(Expression leftOperand, |
| {@required bool isAnd}); |
| |
| /// Call this method after visiting a logical not ("!") expression. |
| /// [notExpression] should be the complete expression. [operand] should be |
| /// the subexpression whose logical value is being negated. |
| void logicalNot_end(Expression notExpression, Expression operand); |
| |
| /// Call this method just after visiting a non-null assertion (`x!`) |
| /// expression. |
| void nonNullAssert_end(Expression operand); |
| |
| /// Call this method after visiting an expression using `?.`. |
| void nullAwareAccess_end(); |
| |
| /// Call this method after visiting a null-aware operator such as `?.`, |
| /// `?..`, `?.[`, or `?..[`. |
| /// |
| /// [target] should be the expression just before the null-aware operator, or |
| /// `null` if the null-aware access starts a cascade section. |
| /// |
| /// Note that [nullAwareAccess_end] should be called after the conclusion |
| /// of any null-shorting that is caused by the `?.`. So, for example, if the |
| /// code being analyzed is `x?.y?.z(x)`, [nullAwareAccess_rightBegin] should |
| /// be called once upon reaching each `?.`, but [nullAwareAccess_end] should |
| /// not be called until after processing the method call to `z(x)`. |
| void nullAwareAccess_rightBegin(Expression target); |
| |
| /// Call this method when encountering an expression that is a `null` literal. |
| void nullLiteral(Expression expression); |
| |
| /// Call this method just after visiting a parenthesized expression. |
| /// |
| /// This is only necessary if the implementation uses a different [Expression] |
| /// object to represent a parenthesized expression and its contents. |
| void parenthesizedExpression( |
| Expression outerExpression, Expression innerExpression); |
| |
| /// Retrieves the type that the [variable] is promoted to, if the [variable] |
| /// is currently promoted. Otherwise returns `null`. |
| /// |
| /// For testing only. Please use [variableRead] instead. |
| @visibleForTesting |
| Type promotedType(Variable variable); |
| |
| /// Call this method just before visiting one of the cases in the body of a |
| /// switch statement. See [switchStatement_expressionEnd] for details. |
| /// |
| /// [hasLabel] indicates whether the case has any labels. |
| /// |
| /// [node] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the switch statement. |
| void switchStatement_beginCase(bool hasLabel, Node node); |
| |
| /// Call this method just after visiting the body of a switch statement. See |
| /// [switchStatement_expressionEnd] for details. |
| /// |
| /// [isExhaustive] indicates whether the switch statement had a "default" |
| /// case, or is based on an enumeration and all the enumeration constants |
| /// were listed in cases. |
| void switchStatement_end(bool isExhaustive); |
| |
| /// Call this method just after visiting the expression part of a switch |
| /// statement. |
| /// |
| /// The order of visiting a switch statement should be: |
| /// - Visit the switch expression. |
| /// - Call [switchStatement_expressionEnd]. |
| /// - For each switch case (including the default case, if any): |
| /// - Call [switchStatement_beginCase]. |
| /// - Visit the case. |
| /// - Call [switchStatement_end]. |
| void switchStatement_expressionEnd(Statement switchStatement); |
| |
| /// Call this method just before visiting the body of a "try/catch" statement. |
| /// |
| /// The order of visiting a "try/catch" statement should be: |
| /// - Call [tryCatchStatement_bodyBegin] |
| /// - Visit the try block |
| /// - Call [tryCatchStatement_bodyEnd] |
| /// - For each catch block: |
| /// - Call [tryCatchStatement_catchBegin] |
| /// - Call [initialize] for the exception and stack trace variables |
| /// - Visit the catch block |
| /// - Call [tryCatchStatement_catchEnd] |
| /// - Call [tryCatchStatement_end] |
| /// |
| /// The order of visiting a "try/catch/finally" statement should be: |
| /// - Call [tryFinallyStatement_bodyBegin] |
| /// - Call [tryCatchStatement_bodyBegin] |
| /// - Visit the try block |
| /// - Call [tryCatchStatement_bodyEnd] |
| /// - For each catch block: |
| /// - Call [tryCatchStatement_catchBegin] |
| /// - Call [initialize] for the exception and stack trace variables |
| /// - Visit the catch block |
| /// - Call [tryCatchStatement_catchEnd] |
| /// - Call [tryCatchStatement_end] |
| /// - Call [tryFinallyStatement_finallyBegin] |
| /// - Visit the finally block |
| /// - Call [tryFinallyStatement_end] |
| void tryCatchStatement_bodyBegin(); |
| |
| /// Call this method just after visiting the body of a "try/catch" statement. |
| /// See [tryCatchStatement_bodyBegin] for details. |
| /// |
| /// [body] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the "try" part of the try/catch statement. |
| void tryCatchStatement_bodyEnd(Node body); |
| |
| /// Call this method just before visiting a catch clause of a "try/catch" |
| /// statement. See [tryCatchStatement_bodyBegin] for details. |
| /// |
| /// [exceptionVariable] should be the exception variable declared by the catch |
| /// clause, or `null` if there is no exception variable. Similar for |
| /// [stackTraceVariable]. |
| void tryCatchStatement_catchBegin( |
| Variable exceptionVariable, Variable stackTraceVariable); |
| |
| /// Call this method just after visiting a catch clause of a "try/catch" |
| /// statement. See [tryCatchStatement_bodyBegin] for details. |
| void tryCatchStatement_catchEnd(); |
| |
| /// Call this method just after visiting a "try/catch" statement. See |
| /// [tryCatchStatement_bodyBegin] for details. |
| void tryCatchStatement_end(); |
| |
| /// Call this method just before visiting the body of a "try/finally" |
| /// statement. |
| /// |
| /// The order of visiting a "try/finally" statement should be: |
| /// - Call [tryFinallyStatement_bodyBegin] |
| /// - Visit the try block |
| /// - Call [tryFinallyStatement_finallyBegin] |
| /// - Visit the finally block |
| /// - Call [tryFinallyStatement_end] |
| /// |
| /// See [tryCatchStatement_bodyBegin] for the order of visiting a |
| /// "try/catch/finally" statement. |
| void tryFinallyStatement_bodyBegin(); |
| |
| /// Call this method just after visiting a "try/finally" statement. |
| /// See [tryFinallyStatement_bodyBegin] for details. |
| /// |
| /// [finallyBlock] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the "finally" part of the try/finally |
| /// statement. |
| void tryFinallyStatement_end(Node finallyBlock); |
| |
| /// Call this method just before visiting the finally block of a "try/finally" |
| /// statement. See [tryFinallyStatement_bodyBegin] for details. |
| /// |
| /// [body] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the "try" part of the try/finally |
| /// statement. |
| void tryFinallyStatement_finallyBegin(Node body); |
| |
| /// Call this method when encountering an expression that reads the value of |
| /// a variable. |
| /// |
| /// If the variable's type is currently promoted, the promoted type is |
| /// returned. Otherwise `null` is returned. |
| Type variableRead(Expression expression, Variable variable); |
| |
| /// Call this method after visiting the condition part of a "while" statement. |
| /// [whileStatement] should be the full while statement. [condition] should |
| /// be the condition part of the while statement. |
| void whileStatement_bodyBegin(Statement whileStatement, Expression condition); |
| |
| /// Call this method before visiting the condition part of a "while" |
| /// statement. |
| /// |
| /// [node] should be the same node that was passed to |
| /// [AssignedVariables.endNode] for the while statement. |
| void whileStatement_conditionBegin(Node node); |
| |
| /// Call this method after visiting a "while" statement. |
| void whileStatement_end(); |
| |
| /// Register write of the given [variable] in the current state. |
| /// [writtenType] should be the type of the value that was written. |
| void write(Variable variable, Type writtenType); |
| } |
| |
| /// Alternate implementation of [FlowAnalysis] that prints out inputs and output |
| /// at the API boundary, for assistance in debugging. |
| class FlowAnalysisDebug<Node, Statement extends Node, Expression, Variable, |
| Type> implements FlowAnalysis<Node, Statement, Expression, Variable, Type> { |
| _FlowAnalysisImpl<Node, Statement, Expression, Variable, Type> _wrapped; |
| |
| bool _exceptionOccurred = false; |
| |
| factory FlowAnalysisDebug(TypeOperations<Variable, Type> typeOperations, |
| AssignedVariables<Node, Variable> assignedVariables) { |
| print('FlowAnalysisDebug()'); |
| return new FlowAnalysisDebug._( |
| new _FlowAnalysisImpl(typeOperations, assignedVariables)); |
| } |
| |
| FlowAnalysisDebug._(this._wrapped); |
| |
| @override |
| bool get isReachable => |
| _wrap('isReachable', () => _wrapped.isReachable, isQuery: true); |
| |
| @override |
| void asExpression_end(Expression subExpression, Type type) { |
| _wrap('asExpression_end($subExpression, $type)', |
| () => _wrapped.asExpression_end(subExpression, type)); |
| } |
| |
| @override |
| void assert_afterCondition(Expression condition) { |
| _wrap('assert_afterCondition($condition)', |
| () => _wrapped.assert_afterCondition(condition)); |
| } |
| |
| @override |
| void assert_begin() { |
| _wrap('assert_begin()', () => _wrapped.assert_begin()); |
| } |
| |
| @override |
| void assert_end() { |
| _wrap('assert_end()', () => _wrapped.assert_end()); |
| } |
| |
| @override |
| void booleanLiteral(Expression expression, bool value) { |
| _wrap('booleanLiteral($expression, $value)', |
| () => _wrapped.booleanLiteral(expression, value)); |
| } |
| |
| @override |
| void conditional_elseBegin(Expression thenExpression) { |
| _wrap('conditional_elseBegin($thenExpression', |
| () => _wrapped.conditional_elseBegin(thenExpression)); |
| } |
| |
| @override |
| void conditional_end( |
| Expression conditionalExpression, Expression elseExpression) { |
| _wrap('conditional_end($conditionalExpression, $elseExpression', |
| () => _wrapped.conditional_end(conditionalExpression, elseExpression)); |
| } |
| |
| @override |
| void conditional_thenBegin(Expression condition) { |
| _wrap('conditional_thenBegin($condition)', |
| () => _wrapped.conditional_thenBegin(condition)); |
| } |
| |
| @override |
| void declare(Variable variable, bool initialized) { |
| _wrap('declare($variable, $initialized)', |
| () => _wrapped.declare(variable, initialized)); |
| } |
| |
| @override |
| void doStatement_bodyBegin(Statement doStatement) { |
| return _wrap('doStatement_bodyBegin($doStatement)', |
| () => _wrapped.doStatement_bodyBegin(doStatement)); |
| } |
| |
| @override |
| void doStatement_conditionBegin() { |
| return _wrap('doStatement_conditionBegin()', |
| () => _wrapped.doStatement_conditionBegin()); |
| } |
| |
| @override |
| void doStatement_end(Expression condition) { |
| return _wrap('doStatement_end($condition)', |
| () => _wrapped.doStatement_end(condition)); |
| } |
| |
| @override |
| void equalityOp_end(Expression wholeExpression, Expression rightOperand, |
| {bool notEqual = false}) { |
| _wrap( |
| 'equalityOp_end($wholeExpression, $rightOperand, notEqual: $notEqual)', |
| () => _wrapped.equalityOp_end(wholeExpression, rightOperand, |
| notEqual: notEqual)); |
| } |
| |
| @override |
| void equalityOp_rightBegin(Expression leftOperand) { |
| _wrap('equalityOp_rightBegin($leftOperand)', |
| () => _wrapped.equalityOp_rightBegin(leftOperand)); |
| } |
| |
| @override |
| void finish() { |
| if (_exceptionOccurred) { |
| _wrap('finish() (skipped)', () {}, isPure: true); |
| } else { |
| _wrap('finish()', () => _wrapped.finish(), isPure: true); |
| } |
| } |
| |
| @override |
| void for_bodyBegin(Statement node, Expression condition) { |
| _wrap('for_bodyBegin($node, $condition)', |
| () => _wrapped.for_bodyBegin(node, condition)); |
| } |
| |
| @override |
| void for_conditionBegin(Node node) { |
| _wrap('for_conditionBegin($node)', () => _wrapped.for_conditionBegin(node)); |
| } |
| |
| @override |
| void for_end() { |
| _wrap('for_end()', () => _wrapped.for_end()); |
| } |
| |
| @override |
| void for_updaterBegin() { |
| _wrap('for_updaterBegin()', () => _wrapped.for_updaterBegin()); |
| } |
| |
| @override |
| void forEach_bodyBegin(Node node, Variable loopVariable, Type writtenType) { |
| return _wrap('forEach_bodyBegin($node, $loopVariable, $writtenType)', |
| () => _wrapped.forEach_bodyBegin(node, loopVariable, writtenType)); |
| } |
| |
| @override |
| void forEach_end() { |
| return _wrap('forEach_end()', () => _wrapped.forEach_end()); |
| } |
| |
| @override |
| void functionExpression_begin(Node node) { |
| _wrap('functionExpression_begin($node)', |
| () => _wrapped.functionExpression_begin(node)); |
| } |
| |
| @override |
| void functionExpression_end() { |
| _wrap('functionExpression_end()', () => _wrapped.functionExpression_end()); |
| } |
| |
| @override |
| void handleBreak(Statement target) { |
| _wrap('handleBreak($target)', () => _wrapped.handleBreak(target)); |
| } |
| |
| @override |
| void handleContinue(Statement target) { |
| _wrap('handleContinue($target)', () => _wrapped.handleContinue(target)); |
| } |
| |
| @override |
| void handleExit() { |
| _wrap('handleExit()', () => _wrapped.handleExit()); |
| } |
| |
| @override |
| void ifNullExpression_end() { |
| return _wrap( |
| 'ifNullExpression_end()', () => _wrapped.ifNullExpression_end()); |
| } |
| |
| @override |
| void ifNullExpression_rightBegin(Expression leftHandSide) { |
| return _wrap('ifNullExpression_rightBegin($leftHandSide)', |
| () => _wrapped.ifNullExpression_rightBegin(leftHandSide)); |
| } |
| |
| @override |
| void ifStatement_elseBegin() { |
| return _wrap( |
| 'ifStatement_elseBegin()', () => _wrapped.ifStatement_elseBegin()); |
| } |
| |
| @override |
| void ifStatement_end(bool hasElse) { |
| _wrap('ifStatement_end($hasElse)', () => _wrapped.ifStatement_end(hasElse)); |
| } |
| |
| @override |
| void ifStatement_thenBegin(Expression condition) { |
| _wrap('ifStatement_thenBegin($condition)', |
| () => _wrapped.ifStatement_thenBegin(condition)); |
| } |
| |
| @override |
| bool isAssigned(Variable variable) { |
| return _wrap('isAssigned($variable)', () => _wrapped.isAssigned(variable), |
| isQuery: true); |
| } |
| |
| @override |
| void isExpression_end(Expression isExpression, Expression subExpression, |
| bool isNot, Type type) { |
| _wrap( |
| 'isExpression_end($isExpression, $subExpression, $isNot, $type)', |
| () => _wrapped.isExpression_end( |
| isExpression, subExpression, isNot, type)); |
| } |
| |
| @override |
| bool isUnassigned(Variable variable) { |
| return _wrap('isUnassigned($variable)', () => _wrapped.isAssigned(variable), |
| isQuery: true); |
| } |
| |
| @override |
| void labeledStatement_begin(Node node) { |
| return _wrap('labeledStatement_begin($node)', |
| () => _wrapped.labeledStatement_begin(node)); |
| } |
| |
| @override |
| void labeledStatement_end() { |
| return _wrap( |
| 'labeledStatement_end()', () => _wrapped.labeledStatement_end()); |
| } |
| |
| @override |
| void logicalBinaryOp_end(Expression wholeExpression, Expression rightOperand, |
| {@required bool isAnd}) { |
| _wrap( |
| 'logicalBinaryOp_end($wholeExpression, $rightOperand, isAnd: $isAnd)', |
| () => _wrapped.logicalBinaryOp_end(wholeExpression, rightOperand, |
| isAnd: isAnd)); |
| } |
| |
| @override |
| void logicalBinaryOp_rightBegin(Expression leftOperand, |
| {@required bool isAnd}) { |
| _wrap('logicalBinaryOp_rightBegin($leftOperand, isAnd: $isAnd)', |
| () => _wrapped.logicalBinaryOp_rightBegin(leftOperand, isAnd: isAnd)); |
| } |
| |
| @override |
| void logicalNot_end(Expression notExpression, Expression operand) { |
| return _wrap('logicalNot_end($notExpression, $operand)', |
| () => _wrapped.logicalNot_end(notExpression, operand)); |
| } |
| |
| @override |
| void nonNullAssert_end(Expression operand) { |
| return _wrap('nonNullAssert_end($operand)', |
| () => _wrapped.nonNullAssert_end(operand)); |
| } |
| |
| @override |
| void nullAwareAccess_end() { |
| _wrap('nullAwareAccess_end()', () => _wrapped.nullAwareAccess_end()); |
| } |
| |
| @override |
| void nullAwareAccess_rightBegin(Expression target) { |
| _wrap('nullAwareAccess_rightBegin($target)', |
| () => _wrapped.nullAwareAccess_rightBegin(target)); |
| } |
| |
| @override |
| void nullLiteral(Expression expression) { |
| _wrap('nullLiteral($expression)', () => _wrapped.nullLiteral(expression)); |
| } |
| |
| @override |
| void parenthesizedExpression( |
| Expression outerExpression, Expression innerExpression) { |
| _wrap( |
| 'parenthesizedExpression($outerExpression, $innerExpression)', |
| () => |
| _wrapped.parenthesizedExpression(outerExpression, innerExpression)); |
| } |
| |
| @override |
| Type promotedType(Variable variable) { |
| return _wrap( |
| 'promotedType($variable)', () => _wrapped.promotedType(variable), |
| isQuery: true); |
| } |
| |
| @override |
| void switchStatement_beginCase(bool hasLabel, Node node) { |
| _wrap('switchStatement_beginCase($hasLabel, $node)', |
| () => _wrapped.switchStatement_beginCase(hasLabel, node)); |
| } |
| |
| @override |
| void switchStatement_end(bool isExhaustive) { |
| _wrap('switchStatement_end($isExhaustive)', |
| () => _wrapped.switchStatement_end(isExhaustive)); |
| } |
| |
| @override |
| void switchStatement_expressionEnd(Statement switchStatement) { |
| _wrap('switchStatement_expressionEnd($switchStatement)', |
| () => _wrapped.switchStatement_expressionEnd(switchStatement)); |
| } |
| |
| @override |
| void tryCatchStatement_bodyBegin() { |
| return _wrap('tryCatchStatement_bodyBegin()', |
| () => _wrapped.tryCatchStatement_bodyBegin()); |
| } |
| |
| @override |
| void tryCatchStatement_bodyEnd(Node body) { |
| return _wrap('tryCatchStatement_bodyEnd($body)', |
| () => _wrapped.tryCatchStatement_bodyEnd(body)); |
| } |
| |
| @override |
| void tryCatchStatement_catchBegin( |
| Variable exceptionVariable, Variable stackTraceVariable) { |
| return _wrap( |
| 'tryCatchStatement_catchBegin($exceptionVariable, $stackTraceVariable)', |
| () => _wrapped.tryCatchStatement_catchBegin( |
| exceptionVariable, stackTraceVariable)); |
| } |
| |
| @override |
| void tryCatchStatement_catchEnd() { |
| return _wrap('tryCatchStatement_catchEnd()', |
| () => _wrapped.tryCatchStatement_catchEnd()); |
| } |
| |
| @override |
| void tryCatchStatement_end() { |
| return _wrap( |
| 'tryCatchStatement_end()', () => _wrapped.tryCatchStatement_end()); |
| } |
| |
| @override |
| void tryFinallyStatement_bodyBegin() { |
| return _wrap('tryFinallyStatement_bodyBegin()', |
| () => _wrapped.tryFinallyStatement_bodyBegin()); |
| } |
| |
| @override |
| void tryFinallyStatement_end(Node finallyBlock) { |
| return _wrap('tryFinallyStatement_end($finallyBlock)', |
| () => _wrapped.tryFinallyStatement_end(finallyBlock)); |
| } |
| |
| @override |
| void tryFinallyStatement_finallyBegin(Node body) { |
| return _wrap('tryFinallyStatement_finallyBegin($body)', |
| () => _wrapped.tryFinallyStatement_finallyBegin(body)); |
| } |
| |
| @override |
| Type variableRead(Expression expression, Variable variable) { |
| return _wrap('variableRead($expression, $variable)', |
| () => _wrapped.variableRead(expression, variable), |
| isQuery: true, isPure: false); |
| } |
| |
| @override |
| void whileStatement_bodyBegin( |
| Statement whileStatement, Expression condition) { |
| return _wrap('whileStatement_bodyBegin($whileStatement, $condition)', |
| () => _wrapped.whileStatement_bodyBegin(whileStatement, condition)); |
| } |
| |
| @override |
| void whileStatement_conditionBegin(Node node) { |
| return _wrap('whileStatement_conditionBegin($node)', |
| () => _wrapped.whileStatement_conditionBegin(node)); |
| } |
| |
| @override |
| void whileStatement_end() { |
| return _wrap('whileStatement_end()', () => _wrapped.whileStatement_end()); |
| } |
| |
| @override |
| void write(Variable variable, Type writtenType) { |
| _wrap('write($variable, $writtenType)', |
| () => _wrapped.write(variable, writtenType)); |
| } |
| |
| T _wrap<T>(String description, T callback(), |
| {bool isQuery: false, bool isPure}) { |
| isPure ??= isQuery; |
| print(description); |
| T result; |
| try { |
| result = callback(); |
| } catch (e, st) { |
| print(' => EXCEPTION $e'); |
| print(' ' + st.toString().replaceAll('\n', '\n ')); |
| _exceptionOccurred = true; |
| rethrow; |
| } |
| if (!isPure) { |
| _wrapped._dumpState(); |
| } |
| if (isQuery) { |
| print(' => $result'); |
| } |
| return result; |
| } |
| } |
| |
| /// An instance of the [FlowModel] class represents the information gathered by |
| /// flow analysis at a single point in the control flow of the function or |
| /// method being analyzed. |
| /// |
| /// Instances of this class are immutable, so the methods below that "update" |
| /// the state actually leave `this` unchanged and return a new state object. |
| @visibleForTesting |
| class FlowModel<Variable, Type> { |
| /// Indicates whether this point in the control flow is reachable. |
| final bool reachable; |
| |
| /// For each variable being tracked by flow analysis, the variable's model. |
| /// |
| /// Flow analysis has no awareness of scope, so variables that are out of |
| /// scope are retained in the map until such time as their declaration no |
| /// longer dominates the control flow. So, for example, if a variable is |
| /// declared inside the `then` branch of an `if` statement, and the `else` |
| /// branch of the `if` statement ends in a `return` statement, then the |
| /// variable remains in the map after the `if` statement ends, even though the |
| /// variable is not in scope anymore. This should not have any effect on |
| /// analysis results for error-free code, because it is an error to refer to a |
| /// variable that is no longer in scope. |
| final Map<Variable, VariableModel<Variable, Type> /*!*/ > variableInfo; |
| |
| /// Variable model for variables that have never been seen before. |
| final VariableModel<Variable, Type> _freshVariableInfo; |
| |
| /// The empty map, used to [join] variables. |
| final Map<Variable, VariableModel<Variable, Type>> _emptyVariableMap = {}; |
| |
| /// Creates a state object with the given [reachable] status. All variables |
| /// are assumed to be unpromoted and already assigned, so joining another |
| /// state with this one will have no effect on it. |
| FlowModel(bool reachable) |
| : this._( |
| reachable, |
| const {}, |
| ); |
| |
| FlowModel._(this.reachable, this.variableInfo) |
| : _freshVariableInfo = new VariableModel.fresh() { |
| assert(() { |
| for (VariableModel<Variable, Type> value in variableInfo.values) { |
| assert(value != null); |
| } |
| return true; |
| }()); |
| } |
| |
| /// Register a declaration of the [variable]. |
| /// Should also be called for function parameters. |
| /// |
| /// A local variable is [initialized] if its declaration has an initializer. |
| /// A function parameter is always initialized, so [initialized] is `true`. |
| FlowModel<Variable, Type> declare(Variable variable, bool initialized) { |
| VariableModel<Variable, Type> newInfoForVar = _freshVariableInfo; |
| if (initialized) { |
| newInfoForVar = newInfoForVar.initialize(); |
| } |
| |
| return _updateVariableInfo(variable, newInfoForVar); |
| } |
| |
| /// Gets the info for the given [variable], creating it if it doesn't exist. |
| VariableModel<Variable, Type> infoFor(Variable variable) => |
| variableInfo[variable] ?? _freshVariableInfo; |
| |
| /// Updates the state to indicate that variables that are not definitely |
| /// unassigned in the [other], or are [written], are also not definitely |
| /// unassigned in the result. |
| FlowModel<Variable, Type> joinUnassigned({ |
| FlowModel<Variable, Type> other, |
| Iterable<Variable> written, |
| }) { |
| Map<Variable, VariableModel<Variable, Type>> newVariableInfo; |
| |
| void markNotUnassigned(Variable variable) { |
| VariableModel<Variable, Type> info = variableInfo[variable]; |
| if (info == null) return; |
| |
| VariableModel<Variable, Type> newInfo = info.markNotUnassigned(); |
| if (identical(newInfo, info)) return; |
| |
| (newVariableInfo ??= |
| new Map<Variable, VariableModel<Variable, Type>>.from( |
| variableInfo))[variable] = newInfo; |
| } |
| |
| if (other != null) { |
| for (Variable variable in other.variableInfo.keys) { |
| VariableModel<Variable, Type> otherInfo = other.variableInfo[variable]; |
| if (!otherInfo.unassigned) { |
| markNotUnassigned(variable); |
| } |
| } |
| } |
| |
| if (written != null) { |
| for (Variable variable in written) { |
| markNotUnassigned(variable); |
| } |
| } |
| |
| if (newVariableInfo == null) return this; |
| |
| return FlowModel<Variable, Type>._(reachable, newVariableInfo); |
| } |
| |
| /// Updates the state to indicate that the given [writtenVariables] are no |
| /// longer promoted; they are presumed to have their declared types. |
| /// |
| /// This is used at the top of loops to conservatively cancel the promotion of |
| /// variables that are modified within the loop, so that we correctly analyze |
| /// code like the following: |
| /// |
| /// if (x is int) { |
| /// x.isEven; // OK, promoted to int |
| /// while (true) { |
| /// x.isEven; // ERROR: promotion lost |
| /// x = 'foo'; |
| /// } |
| /// } |
| /// |
| /// Note that a more accurate analysis would be to iterate to a fixed point, |
| /// and only remove promotions if it can be shown that they aren't restored |
| /// later in the loop body. If we switch to a fixed point analysis, we should |
| /// be able to remove this method. |
| FlowModel<Variable, Type> removePromotedAll( |
| Iterable<Variable> writtenVariables, |
| Iterable<Variable> capturedVariables) { |
| Map<Variable, VariableModel<Variable, Type>> newVariableInfo; |
| for (Variable variable in writtenVariables) { |
| VariableModel<Variable, Type> info = infoFor(variable); |
| if (info.promotedTypes != null) { |
| (newVariableInfo ??= |
| new Map<Variable, VariableModel<Variable, Type>>.from( |
| variableInfo))[variable] = info.discardPromotions(); |
| } |
| } |
| for (Variable variable in capturedVariables) { |
| VariableModel<Variable, Type> info = variableInfo[variable]; |
| if (info == null) { |
| (newVariableInfo ??= |
| new Map<Variable, VariableModel<Variable, Type>>.from( |
| variableInfo))[variable] = new VariableModel<Variable, Type>( |
| null, const [], false, false, true); |
| } else if (!info.writeCaptured) { |
| (newVariableInfo ??= |
| new Map<Variable, VariableModel<Variable, Type>>.from( |
| variableInfo))[variable] = info.writeCapture(); |
| } |
| } |
| if (newVariableInfo == null) return this; |
| return new FlowModel<Variable, Type>._(reachable, newVariableInfo); |
| } |
| |
| /// Updates the state to reflect a control path that is known to have |
| /// previously passed through some [other] state. |
| /// |
| /// Approximately, this method forms the union of the definite assignments and |
| /// promotions in `this` state and the [other] state. More precisely: |
| /// |
| /// The control flow path is considered reachable if both this state and the |
| /// other state are reachable. Variables are considered definitely assigned |
| /// if they were definitely assigned in either this state or the other state. |
| /// Variable type promotions are taken from this state, unless the promotion |
| /// in the other state is more specific, and the variable is "safe". A |
| /// variable is considered safe if there is no chance that it was assigned |
| /// more recently than the "other" state. |
| /// |
| /// This is used after a `try/finally` statement to combine the promotions and |
| /// definite assignments that occurred in the `try` and `finally` blocks |
| /// (where `this` is the state from the `finally` block and `other` is the |
| /// state from the `try` block). Variables that are assigned in the `finally` |
| /// block are considered "unsafe" because the assignment might have cancelled |
| /// the effect of any promotion that occurred inside the `try` block. |
| FlowModel<Variable, Type> restrict( |
| TypeOperations<Variable, Type> typeOperations, |
| FlowModel<Variable, Type> other, |
| Set<Variable> unsafe) { |
| bool newReachable = reachable && other.reachable; |
| |
| Map<Variable, VariableModel<Variable, Type>> newVariableInfo = |
| <Variable, VariableModel<Variable, Type>>{}; |
| bool variableInfoMatchesThis = true; |
| bool variableInfoMatchesOther = true; |
| for (MapEntry<Variable, VariableModel<Variable, Type>> entry |
| in variableInfo.entries) { |
| Variable variable = entry.key; |
| VariableModel<Variable, Type> thisModel = entry.value; |
| VariableModel<Variable, Type> otherModel = other.variableInfo[variable]; |
| if (otherModel == null) { |
| variableInfoMatchesThis = false; |
| continue; |
| } |
| VariableModel<Variable, Type> restricted = thisModel.restrict( |
| typeOperations, otherModel, unsafe.contains(variable)); |
| newVariableInfo[variable] = restricted; |
| if (!identical(restricted, thisModel)) variableInfoMatchesThis = false; |
| if (!identical(restricted, otherModel)) variableInfoMatchesOther = false; |
| } |
| if (variableInfoMatchesOther) { |
| for (Variable variable in other.variableInfo.keys) { |
| if (!variableInfo.containsKey(variable)) { |
| variableInfoMatchesOther = false; |
| break; |
| } |
| } |
| } |
| assert(variableInfoMatchesThis == |
| _variableInfosEqual(newVariableInfo, variableInfo)); |
| assert(variableInfoMatchesOther == |
| _variableInfosEqual(newVariableInfo, other.variableInfo)); |
| if (variableInfoMatchesThis) { |
| newVariableInfo = variableInfo; |
| } else if (variableInfoMatchesOther) { |
| newVariableInfo = other.variableInfo; |
| } |
| |
| return _identicalOrNew(this, other, newReachable, newVariableInfo); |
| } |
| |
| /// Updates the state to indicate whether the control flow path is |
| /// [reachable]. |
| FlowModel<Variable, Type> setReachable(bool reachable) { |
| if (this.reachable == reachable) return this; |
| |
| return new FlowModel<Variable, Type>._(reachable, variableInfo); |
| } |
| |
| @override |
| String toString() => '($reachable, $variableInfo)'; |
| |
| /// Returns an [ExpressionInfo] indicating the result of checking whether the |
| /// given [variable] is non-null. |
| /// |
| /// Note that the state is only changed if the previous type of [variable] was |
| /// potentially nullable. |
| ExpressionInfo<Variable, Type> tryMarkNonNullable( |
| TypeOperations<Variable, Type> typeOperations, Variable variable) { |
| VariableModel<Variable, Type> info = infoFor(variable); |
| if (info.writeCaptured) { |
| return new ExpressionInfo<Variable, Type>(this, this, this); |
| } |
| |
| Type previousType = info.promotedTypes?.last; |
| previousType ??= typeOperations.variableType(variable); |
| |
| Type newType = typeOperations.promoteToNonNull(previousType); |
| if (typeOperations.isSameType(newType, previousType)) { |
| return new ExpressionInfo<Variable, Type>(this, this, this); |
| } |
| assert(typeOperations.isSubtypeOf(newType, previousType)); |
| |
| FlowModel<Variable, Type> modelIfSuccessful = |
| _finishTypeTest(typeOperations, variable, info, null, newType); |
| |
| FlowModel<Variable, Type> modelIfFailed = this; |
| |
| return new ExpressionInfo<Variable, Type>( |
| this, modelIfSuccessful, modelIfFailed); |
| } |
| |
| /// Returns an [ExpressionInfo] indicating the result of casting the given |
| /// [variable] to the given [type], as a consequence of an `as` expression. |
| /// |
| /// Note that the state is only changed if [type] is a subtype of the |
| /// variable's previous (possibly promoted) type. |
| /// |
| /// TODO(paulberry): if the type is non-nullable, should this method mark the |
| /// variable as definitely assigned? Does it matter? |
| FlowModel<Variable, Type> tryPromoteForTypeCast( |
| TypeOperations<Variable, Type> typeOperations, |
| Variable variable, |
| Type type) { |
| VariableModel<Variable, Type> info = infoFor(variable); |
| if (info.writeCaptured) { |
| return this; |
| } |
| |
| Type previousType = info.promotedTypes?.last; |
| previousType ??= typeOperations.variableType(variable); |
| |
| Type newType = typeOperations.tryPromoteToType(type, previousType); |
| if (newType == null || typeOperations.isSameType(newType, previousType)) { |
| return this; |
| } |
| |
| assert(typeOperations.isSubtypeOf(newType, previousType), |
| "Expected $newType to be a subtype of $previousType."); |
| return _finishTypeTest(typeOperations, variable, info, type, newType); |
| } |
| |
| /// Returns an [ExpressionInfo] indicating the result of checking whether the |
| /// given [variable] satisfies the given [type], e.g. as a consequence of an |
| /// `is` expression as the condition of an `if` statement. |
| /// |
| /// Note that the "ifTrue" state is only changed if [type] is a subtype of |
| /// the variable's previous (possibly promoted) type. |
| /// |
| /// TODO(paulberry): if the type is non-nullable, should this method mark the |
| /// variable as definitely assigned? Does it matter? |
| ExpressionInfo<Variable, Type> tryPromoteForTypeCheck( |
| TypeOperations<Variable, Type> typeOperations, |
| Variable variable, |
| Type type) { |
| VariableModel<Variable, Type> info = infoFor(variable); |
| if (info.writeCaptured) { |
| return new ExpressionInfo<Variable, Type>(this, this, this); |
| } |
| |
| Type previousType = info.promotedTypes?.last; |
| previousType ??= typeOperations.variableType(variable); |
| |
| FlowModel<Variable, Type> modelIfSuccessful = this; |
| Type typeIfSuccess = typeOperations.tryPromoteToType(type, previousType); |
| if (typeIfSuccess != null && |
| !typeOperations.isSameType(typeIfSuccess, previousType)) { |
| assert(typeOperations.isSubtypeOf(typeIfSuccess, previousType), |
| "Expected $typeIfSuccess to be a subtype of $previousType."); |
| modelIfSuccessful = |
| _finishTypeTest(typeOperations, variable, info, type, typeIfSuccess); |
| } |
| |
| Type factoredType = typeOperations.factor(previousType, type); |
| Type typeIfFailed = typeOperations.isSameType(factoredType, previousType) |
| ? null |
| : factoredType; |
| FlowModel<Variable, Type> modelIfFailed = |
| _finishTypeTest(typeOperations, variable, info, type, typeIfFailed); |
| |
| return new ExpressionInfo<Variable, Type>( |
| this, modelIfSuccessful, modelIfFailed); |
| } |
| |
| /// Updates the state to indicate that an assignment was made to the given |
| /// [variable]. The variable is marked as definitely assigned, and any |
| /// previous type promotion is removed. |
| FlowModel<Variable, Type> write(Variable variable, Type writtenType, |
| TypeOperations<Variable, Type> typeOperations) { |
| VariableModel<Variable, Type> infoForVar = variableInfo[variable]; |
| if (infoForVar == null) return this; |
| |
| VariableModel<Variable, Type> newInfoForVar = |
| infoForVar.write(variable, writtenType, typeOperations); |
| if (identical(newInfoForVar, infoForVar)) return this; |
| |
| return _updateVariableInfo(variable, newInfoForVar); |
| } |
| |
| /// Common algorithm for [tryMarkNonNullable], [tryPromoteForTypeCast], |
| /// and [tryPromoteForTypeCheck]. Builds a [FlowModel] object describing the |
| /// effect of updating the [variable] by adding the [testedType] to the |
| /// list of tested types (if not `null`, and not there already), adding the |
| /// [promotedType] to the chain of promoted types. |
| /// |
| /// Preconditions: |
| /// - [info] should be the result of calling `infoFor(variable)` |
| /// - [promotedType] should be a subtype of the currently-promoted type (i.e. |
| /// no redundant or side-promotions) |
| /// - The variable should not be write-captured. |
| FlowModel<Variable, Type> _finishTypeTest( |
| TypeOperations<Variable, Type> typeOperations, |
| Variable variable, |
| VariableModel<Variable, Type> info, |
| Type testedType, |
| Type promotedType, |
| ) { |
| List<Type> newTested = info.tested; |
| if (testedType != null) { |
| newTested = VariableModel._addTypeToUniqueList( |
| info.tested, testedType, typeOperations); |
| } |
| |
| List<Type> newPromotedTypes = info.promotedTypes; |
| if (promotedType != null) { |
| newPromotedTypes = |
| VariableModel._addToPromotedTypes(info.promotedTypes, promotedType); |
| } |
| |
| return identical(newTested, info.tested) && |
| identical(newPromotedTypes, info.promotedTypes) |
| ? this |
| : _updateVariableInfo( |
| variable, |
| new VariableModel<Variable, Type>(newPromotedTypes, newTested, |
| info.assigned, info.unassigned, info.writeCaptured)); |
| } |
| |
| /// Returns a new [FlowModel] where the information for [variable] is replaced |
| /// with [model]. |
| FlowModel<Variable, Type> _updateVariableInfo( |
| Variable variable, VariableModel<Variable, Type> model) { |
| Map<Variable, VariableModel<Variable, Type>> newVariableInfo = |
| new Map<Variable, VariableModel<Variable, Type>>.from(variableInfo); |
| newVariableInfo[variable] = model; |
| return new FlowModel<Variable, Type>._(reachable, newVariableInfo); |
| } |
| |
| /// Forms a new state to reflect a control flow path that might have come from |
| /// either `this` or the [other] state. |
| /// |
| /// The control flow path is considered reachable if either of the input |
| /// states is reachable. Variables are considered definitely assigned if they |
| /// were definitely assigned in both of the input states. Variable promotions |
| /// are kept only if they are common to both input states; if a variable is |
| /// promoted to one type in one state and a subtype in the other state, the |
| /// less specific type promotion is kept. |
| static FlowModel<Variable, Type> join<Variable, Type>( |
| TypeOperations<Variable, Type> typeOperations, |
| FlowModel<Variable, Type> first, |
| FlowModel<Variable, Type> second, |
| Map<Variable, VariableModel<Variable, Type>> emptyVariableMap, |
| ) { |
| if (first == null) return second; |
| if (second == null) return first; |
| |
| if (first.reachable && !second.reachable) return first; |
| if (!first.reachable && second.reachable) return second; |
| |
| bool newReachable = first.reachable || second.reachable; |
| Map<Variable, VariableModel<Variable, Type>> newVariableInfo = |
| FlowModel.joinVariableInfo(typeOperations, first.variableInfo, |
| second.variableInfo, emptyVariableMap); |
| |
| return FlowModel._identicalOrNew( |
| first, second, newReachable, newVariableInfo); |
| } |
| |
| /// Joins two "variable info" maps. See [join] for details. |
| @visibleForTesting |
| static Map<Variable, VariableModel<Variable, Type>> |
| joinVariableInfo<Variable, Type>( |
| TypeOperations<Variable, Type> typeOperations, |
| Map<Variable, VariableModel<Variable, Type>> first, |
| Map<Variable, VariableModel<Variable, Type>> second, |
| Map<Variable, VariableModel<Variable, Type>> emptyMap, |
| ) { |
| if (identical(first, second)) return first; |
| if (first.isEmpty || second.isEmpty) { |
| return emptyMap; |
| } |
| |
| Map<Variable, VariableModel<Variable, Type>> result = |
| <Variable, VariableModel<Variable, Type>>{}; |
| bool alwaysFirst = true; |
| bool alwaysSecond = true; |
| for (MapEntry<Variable, VariableModel<Variable, Type>> entry |
| in first.entries) { |
| Variable variable = entry.key; |
| VariableModel<Variable, Type> secondModel = second[variable]; |
| if (secondModel == null) { |
| alwaysFirst = false; |
| } else { |
| VariableModel<Variable, Type> joined = |
| VariableModel.join<Variable, Type>( |
| typeOperations, entry.value, secondModel); |
| result[variable] = joined; |
| if (!identical(joined, entry.value)) alwaysFirst = false; |
| if (!identical(joined, secondModel)) alwaysSecond = false; |
| } |
| } |
| |
| if (alwaysFirst) return first; |
| if (alwaysSecond && result.length == second.length) return second; |
| if (result.isEmpty) return emptyMap; |
| return result; |
| } |
| |
| /// Creates a new [FlowModel] object, unless it is equivalent to either |
| /// [first] or [second], in which case one of those objects is re-used. |
| static FlowModel<Variable, Type> _identicalOrNew<Variable, Type>( |
| FlowModel<Variable, Type> first, |
| FlowModel<Variable, Type> second, |
| bool newReachable, |
| Map<Variable, VariableModel<Variable, Type>> newVariableInfo) { |
| if (first.reachable == newReachable && |
| identical(first.variableInfo, newVariableInfo)) { |
| return first; |
| } |
| if (second.reachable == newReachable && |
| identical(second.variableInfo, newVariableInfo)) { |
| return second; |
| } |
| |
| return new FlowModel<Variable, Type>._(newReachable, newVariableInfo); |
| } |
| |
| /// Determines whether the given "variableInfo" maps are equivalent. |
| /// |
| /// The equivalence check is shallow; if two variables' models are not |
| /// identical, we return `false`. |
| static bool _variableInfosEqual<Variable, Type>( |
| Map<Variable, VariableModel<Variable, Type>> p1, |
| Map<Variable, VariableModel<Variable, Type>> p2) { |
| if (p1.length != p2.length) return false; |
| if (!p1.keys.toSet().containsAll(p2.keys)) return false; |
| for (MapEntry<Variable, VariableModel<Variable, Type>> entry |
| in p1.entries) { |
| VariableModel<Variable, Type> p1Value = entry.value; |
| VariableModel<Variable, Type> p2Value = p2[entry.key]; |
| if (!identical(p1Value, p2Value)) { |
| return false; |
| } |
| } |
| return true; |
| } |
| } |
| |
| /// Operations on types, abstracted from concrete type interfaces. |
| abstract class TypeOperations<Variable, Type> { |
| /// Returns the "remainder" of [from] when [what] has been removed from |
| /// consideration by an instance check. |
| Type factor(Type from, Type what); |
| |
| /// Return `true` if the [variable] is a local variable (not a formal |
| /// parameter), and it has no declared type (no explicit type, and not |
| /// initializer). |
| bool isLocalVariableWithoutDeclaredType(Variable variable); |
| |
| /// Returns `true` if [type1] and [type2] are the same type. |
| bool isSameType(Type type1, Type type2); |
| |
| /// Return `true` if the [leftType] is a subtype of the [rightType]. |
| bool isSubtypeOf(Type leftType, Type rightType); |
| |
| /// Returns the non-null promoted version of [type]. |
| /// |
| /// Note that some types don't have a non-nullable version (e.g. |
| /// `FutureOr<int?>`), so [type] may be returned even if it is nullable. |
| Type /*!*/ promoteToNonNull(Type type); |
| |
| /// Tries to promote to the first type from the second type, and returns the |
| /// promoted type if it succeeds, otherwise null. |
| Type tryPromoteToType(Type to, Type from); |
| |
| /// Return the static type of the given [variable]. |
| Type variableType(Variable variable); |
| } |
| |
| /// An instance of the [VariableModel] class represents the information gathered |
| /// by flow analysis for a single variable at a single point in the control flow |
| /// of the function or method being analyzed. |
| /// |
| /// Instances of this class are immutable, so the methods below that "update" |
| /// the state actually leave `this` unchanged and return a new state object. |
| @visibleForTesting |
| class VariableModel<Variable, Type> { |
| /// Sequence of types that the variable has been promoted to, where each |
| /// element of the sequence is a subtype of the previous. Null if the |
| /// variable hasn't been promoted. |
| final List<Type> promotedTypes; |
| |
| /// List of types that the variable has been tested against in all code paths |
| /// leading to the given point in the source code. |
| final List<Type> tested; |
| |
| /// Indicates whether the variable has definitely been assigned. |
| final bool assigned; |
| |
| /// Indicates whether the variable is unassigned. |
| final bool unassigned; |
| |
| /// Indicates whether the variable has been write captured. |
| final bool writeCaptured; |
| |
| VariableModel(this.promotedTypes, this.tested, this.assigned, this.unassigned, |
| this.writeCaptured) { |
| assert(!(assigned && unassigned), |
| "Can't be both definitely assigned and unassigned"); |
| assert(promotedTypes == null || promotedTypes.isNotEmpty); |
| assert(!writeCaptured || promotedTypes == null, |
| "Write-captured variables can't be promoted"); |
| assert(!(writeCaptured && unassigned), |
| "Write-captured variables can't be definitely unassigned"); |
| assert(tested != null); |
| } |
| |
| /// Creates a [VariableModel] representing a variable that's never been seen |
| /// before. |
| VariableModel.fresh() |
| : promotedTypes = null, |
| tested = const [], |
| assigned = false, |
| unassigned = true, |
| writeCaptured = false; |
| |
| /// Returns a new [VariableModel] in which any promotions present have been |
| /// dropped. |
| VariableModel<Variable, Type> discardPromotions() { |
| assert(promotedTypes != null, 'No promotions to discard'); |
| return new VariableModel<Variable, Type>( |
| null, tested, assigned, unassigned, writeCaptured); |
| } |
| |
| /// Returns a new [VariableModel] reflecting the fact that the variable was |
| /// just initialized. |
| VariableModel<Variable, Type> initialize() { |
| if (promotedTypes == null && tested.isEmpty && assigned && !unassigned) { |
| return this; |
| } |
| return new VariableModel<Variable, Type>( |
| null, const [], true, false, writeCaptured); |
| } |
| |
| /// Returns a new [VariableModel] reflecting the fact that the variable is |
| /// not definitely unassigned. |
| VariableModel<Variable, Type> markNotUnassigned() { |
| if (!unassigned) return this; |
| |
| return new VariableModel<Variable, Type>( |
| promotedTypes, tested, assigned, false, writeCaptured); |
| } |
| |
| /// Returns an updated model reflect a control path that is known to have |
| /// previously passed through some [other] state. See [FlowModel.restrict] |
| /// for details. |
| VariableModel<Variable, Type> restrict( |
| TypeOperations<Variable, Type> typeOperations, |
| VariableModel<Variable, Type> otherModel, |
| bool unsafe) { |
| List<Type> thisPromotedTypes = promotedTypes; |
| List<Type> otherPromotedTypes = otherModel.promotedTypes; |
| bool newAssigned = assigned || otherModel.assigned; |
| // The variable can only be unassigned in this state if it was also |
| // unassigned in the other state or if the other state didn't complete |
| // normally. For the latter case the resulting state is unreachable but to |
| // avoid creating a variable model that is both assigned and unassigned we |
| // take the intersection below. |
| // |
| // This situation can occur in try-finally like: |
| // |
| // method() { |
| // var local; |
| // try { |
| // local = 0; |
| // return; // assigned |
| // } finally { |
| // local; // unassigned |
| // } |
| // local; // unreachable state |
| // } |
| // |
| bool newUnassigned = unassigned && otherModel.unassigned; |
| bool newWriteCaptured = writeCaptured || otherModel.writeCaptured; |
| List<Type> newPromotedTypes; |
| if (unsafe) { |
| // There was an assignment to the variable in the "this" path, so none of |
| // the promotions from the "other" path can be used. |
| newPromotedTypes = thisPromotedTypes; |
| } else if (otherPromotedTypes == null) { |
| // The other promotion chain contributes nothing so we just use this |
| // promotion chain directly. |
| newPromotedTypes = thisPromotedTypes; |
| } else if (thisPromotedTypes == null) { |
| // This promotion chain contributes nothing so we just use the other |
| // promotion chain directly. |
| newPromotedTypes = otherPromotedTypes; |
| } else { |
| // Start with otherPromotedTypes and apply each of the promotions in |
| // thisPromotedTypes (discarding any that don't follow the ordering |
| // invariant) |
| newPromotedTypes = otherPromotedTypes; |
| Type otherPromotedType = otherPromotedTypes.last; |
| for (int i = 0; i < thisPromotedTypes.length; i++) { |
| Type nextType = thisPromotedTypes[i]; |
| if (typeOperations.isSubtypeOf(nextType, otherPromotedType) && |
| !typeOperations.isSameType(nextType, otherPromotedType)) { |
| newPromotedTypes = otherPromotedTypes.toList() |
| ..addAll(thisPromotedTypes.skip(i)); |
| break; |
| } |
| } |
| } |
| return _identicalOrNew(this, otherModel, newPromotedTypes, tested, |
| newAssigned, newUnassigned, newWriteCaptured); |
| } |
| |
| @override |
| String toString() { |
| List<String> parts = []; |
| if (promotedTypes != null) { |
| parts.add('promotedTypes: $promotedTypes'); |
| } |
| if (tested.isNotEmpty) { |
| parts.add('tested: $tested'); |
| } |
| if (assigned) { |
| parts.add('assigned: true'); |
| } |
| if (!unassigned) { |
| parts.add('unassigned: false'); |
| } |
| if (writeCaptured) { |
| parts.add('writeCaptured: true'); |
| } |
| return 'VariableModel(${parts.join(', ')})'; |
| } |
| |
| /// Returns a new [VariableModel] reflecting the fact that the variable was |
| /// just written to. |
| VariableModel<Variable, Type> write(Variable variable, Type writtenType, |
| TypeOperations<Variable, Type> typeOperations) { |
| if (writeCaptured) { |
| return new VariableModel<Variable, Type>( |
| promotedTypes, tested, true, false, writeCaptured); |
| } |
| |
| if (_isPromotableViaInitialization(typeOperations, variable)) { |
| return new VariableModel<Variable, Type>( |
| [writtenType], tested, true, false, writeCaptured); |
| } |
| |
| List<Type> newPromotedTypes = _demoteViaAssignment( |
| writtenType, |
| typeOperations, |
| ); |
| |
| Type declaredType = typeOperations.variableType(variable); |
| newPromotedTypes = _tryPromoteToTypeOfInterest( |
| typeOperations, declaredType, newPromotedTypes, writtenType); |
| if (identical(promotedTypes, newPromotedTypes) && assigned) return this; |
| |
| List<Type> newTested; |
| if (newPromotedTypes == null && promotedTypes != null) { |
| newTested = const []; |
| } else { |
| newTested = tested; |
| } |
| |
| return new VariableModel<Variable, Type>( |
| newPromotedTypes, newTested, true, false, writeCaptured); |
| } |
| |
| /// Returns a new [VariableModel] reflecting the fact that the variable has |
| /// been write-captured. |
| VariableModel<Variable, Type> writeCapture() { |
| return new VariableModel<Variable, Type>( |
| null, const [], assigned, false, true); |
| } |
| |
| List<Type> _demoteViaAssignment( |
| Type writtenType, |
| TypeOperations<Variable, Type> typeOperations, |
| ) { |
| if (promotedTypes == null) { |
| return null; |
| } |
| |
| int numElementsToKeep = promotedTypes.length; |
| for (;; numElementsToKeep--) { |
| if (numElementsToKeep == 0) { |
| return null; |
| } |
| Type promoted = promotedTypes[numElementsToKeep - 1]; |
| if (typeOperations.isSubtypeOf(writtenType, promoted)) { |
| if (numElementsToKeep == promotedTypes.length) { |
| return promotedTypes; |
| } |
| return promotedTypes.sublist(0, numElementsToKeep); |
| } |
| } |
| } |
| |
| /// We say that a variable `x` is promotable via initialization given |
| /// variable model `VM` if `x` is a local variable (not a formal parameter) |
| /// and: |
| /// * VM = VariableModel(declared, promoted, tested, |
| /// assigned, unassigned, captured) |
| /// * and `captured` is false |
| /// * and `promoted` is empty |
| /// * and `x` is declared with no explicit type and no initializer |
| /// * and `assigned` is false and `unassigned` is true |
| bool _isPromotableViaInitialization<Variable>( |
| TypeOperations<Variable, Type> typeOperations, |
| Variable variable, |
| ) { |
| return !writeCaptured && |
| !assigned && |
| unassigned && |
| promotedTypes == null && |
| typeOperations.isLocalVariableWithoutDeclaredType(variable); |
| } |
| |
| /// Determines whether a variable with the given [promotedTypes] should be |
| /// promoted to [writtenType] based on types of interest. If it should, |
| /// returns an updated promotion chain; otherwise returns [promotedTypes] |
| /// unchanged. |
| /// |
| /// Note that since promotions chains are considered immutable, if promotion |
| /// is required, a new promotion chain will be created and returned. |
| List<Type> _tryPromoteToTypeOfInterest( |
| TypeOperations<Variable, Type> typeOperations, |
| Type declaredType, |
| List<Type> promotedTypes, |
| Type writtenType) { |
| assert(!writeCaptured); |
| |
| // Figure out if we have any promotion candidates (types that are a |
| // supertype of writtenType and a proper subtype of the currently-promoted |
| // type). If at any point we find an exact match, we take it immediately. |
| Type currentlyPromotedType = promotedTypes?.last; |
| |
| List<Type> result; |
| List<Type> candidates = null; |
| |
| void handleTypeOfInterest(Type type) { |
| // The written type must be a subtype of the type. |
| if (!typeOperations.isSubtypeOf(writtenType, type)) { |
| return; |
| } |
| |
| // Must be more specific that the currently promoted type. |
| if (currentlyPromotedType != null) { |
| if (typeOperations.isSameType(type, currentlyPromotedType)) { |
| return; |
| } |
| if (!typeOperations.isSubtypeOf(type, currentlyPromotedType)) { |
| return; |
| } |
| } |
| |
| // This is precisely the type we want to promote to; take it. |
| if (typeOperations.isSameType(type, writtenType)) { |
| result = _addToPromotedTypes(promotedTypes, writtenType); |
| } |
| |
| if (candidates == null) { |
| candidates = [type]; |
| return; |
| } |
| |
| // Add only unique candidates. |
| if (!_typeListContains(typeOperations, candidates, type)) { |
| candidates.add(type); |
| return; |
| } |
| } |
| |
| // The declared type is always a type of interest, but we never promote |
| // to the declared type. So, try NonNull of it. |
| Type declaredTypeNonNull = typeOperations.promoteToNonNull(declaredType); |
| if (!typeOperations.isSameType(declaredTypeNonNull, declaredType)) { |
| handleTypeOfInterest(declaredTypeNonNull); |
| if (result != null) { |
| return result; |
| } |
| } |
| |
| for (int i = 0; i < tested.length; i++) { |
| Type type = tested[i]; |
| |
| handleTypeOfInterest(type); |
| if (result != null) { |
| return result; |
| } |
| |
| Type typeNonNull = typeOperations.promoteToNonNull(type); |
| if (!typeOperations.isSameType(typeNonNull, type)) { |
| handleTypeOfInterest(typeNonNull); |
| if (result != null) { |
| return result; |
| } |
| } |
| } |
| |
| if (candidates != null) { |
| // Figure out if we have a unique promotion candidate that's a subtype |
| // of all the others. |
| Type promoted; |
| outer: |
| for (int i = 0; i < candidates.length; i++) { |
| for (int j = 0; j < candidates.length; j++) { |
| if (j == i) continue; |
| if (!typeOperations.isSubtypeOf(candidates[i], candidates[j])) { |
| // Not a subtype of all the others. |
| continue outer; |
| } |
| } |
| if (promoted != null) { |
| // Not unique. Do not promote. |
| return promotedTypes; |
| } else { |
| promoted = candidates[i]; |
| } |
| } |
| if (promoted != null) { |
| return _addToPromotedTypes(promotedTypes, promoted); |
| } |
| } |
| // No suitable promotion found. |
| return promotedTypes; |
| } |
| |
| /// Joins two variable models. See [FlowModel.join] for details. |
| static VariableModel<Variable, Type> join<Variable, Type>( |
| TypeOperations<Variable, Type> typeOperations, |
| VariableModel<Variable, Type> first, |
| VariableModel<Variable, Type> second) { |
| List<Type> newPromotedTypes = joinPromotedTypes( |
| first.promotedTypes, second.promotedTypes, typeOperations); |
| bool newAssigned = first.assigned && second.assigned; |
| bool newUnassigned = first.unassigned && second.unassigned; |
| bool newWriteCaptured = first.writeCaptured || second.writeCaptured; |
| List<Type> newTested = newWriteCaptured |
| ? const [] |
| : joinTested(first.tested, second.tested, typeOperations); |
| return _identicalOrNew(first, second, newPromotedTypes, newTested, |
| newAssigned, newUnassigned, newWriteCaptured); |
| } |
| |
| /// Performs the portion of the "join" algorithm that applies to promotion |
| /// chains. Briefly, we intersect given chains. The chains are totally |
| /// ordered subsets of a global partial order. Their intersection is a |
| /// subset of each, and as such is also totally ordered. |
| static List<Type> joinPromotedTypes<Variable, Type>(List<Type> chain1, |
| List<Type> chain2, TypeOperations<Variable, Type> typeOperations) { |
| if (chain1 == null) return chain1; |
| if (chain2 == null) return chain2; |
| |
| int index1 = 0; |
| int index2 = 0; |
| bool skipped1 = false; |
| bool skipped2 = false; |
| List<Type> result; |
| while (index1 < chain1.length && index2 < chain2.length) { |
| var type1 = chain1[index1]; |
| var type2 = chain2[index2]; |
| if (typeOperations.isSameType(type1, type2)) { |
| result ??= <Type>[]; |
| result.add(type1); |
| index1++; |
| index2++; |
| } else if (typeOperations.isSubtypeOf(type2, type1)) { |
| index1++; |
| skipped1 = true; |
| } else if (typeOperations.isSubtypeOf(type1, type2)) { |
| index2++; |
| skipped2 = true; |
| } else { |
| skipped1 = true; |
| skipped2 = true; |
| break; |
| } |
| } |
| |
| if (index1 == chain1.length && !skipped1) return chain1; |
| if (index2 == chain2.length && !skipped2) return chain2; |
| return result; |
| } |
| |
| /// Performs the portion of the "join" algorithm that applies to promotion |
| /// chains. Essentially this performs a set union, with the following |
| /// caveats: |
| /// - The "sets" are represented as lists (since they are expected to be very |
| /// small in real-world cases) |
| /// - The sense of equality for the union operation is determined by |
| /// [TypeOperations.isSameType]. |
| /// - The types of interests lists are considered immutable. |
| static List<Type> joinTested<Variable, Type>(List<Type> types1, |
| List<Type> types2, TypeOperations<Variable, Type> typeOperations) { |
| // Ensure that types1 is the shorter list. |
| if (types1.length > types2.length) { |
| List<Type> tmp = types1; |
| types1 = types2; |
| types2 = tmp; |
| } |
| // Determine the length of the common prefix the two lists share. |
| int shared = 0; |
| for (; shared < types1.length; shared++) { |
| if (!typeOperations.isSameType(types1[shared], types2[shared])) break; |
| } |
| // Use types2 as a starting point and add any entries from types1 that are |
| // not present in it. |
| for (int i = shared; i < types1.length; i++) { |
| Type typeToAdd = types1[i]; |
| if (_typeListContains(typeOperations, types2, typeToAdd)) continue; |
| List<Type> result = types2.toList()..add(typeToAdd); |
| for (i++; i < types1.length; i++) { |
| typeToAdd = types1[i]; |
| if (_typeListContains(typeOperations, types2, typeToAdd)) continue; |
| result.add(typeToAdd); |
| } |
| return result; |
| } |
| // No types needed to be added. |
| return types2; |
| } |
| |
| static List<Type> _addToPromotedTypes<Type>( |
| List<Type> promotedTypes, Type promoted) => |
| promotedTypes == null |
| ? [promoted] |
| : (promotedTypes.toList()..add(promoted)); |
| |
| static List<Type> _addTypeToUniqueList<Variable, Type>(List<Type> types, |
| Type newType, TypeOperations<Variable, Type> typeOperations) { |
| if (_typeListContains(typeOperations, types, newType)) return types; |
| return new List<Type>.from(types)..add(newType); |
| } |
| |
| /// Creates a new [VariableModel] object, unless it is equivalent to either |
| /// [first] or [second], in which case one of those objects is re-used. |
| static VariableModel<Variable, Type> _identicalOrNew<Variable, Type>( |
| VariableModel<Variable, Type> first, |
| VariableModel<Variable, Type> second, |
| List<Type> newPromotedTypes, |
| List<Type> newTested, |
| bool newAssigned, |
| bool newUnassigned, |
| bool newWriteCaptured) { |
| if (identical(first.promotedTypes, newPromotedTypes) && |
| identical(first.tested, newTested) && |
| first.assigned == newAssigned && |
| first.unassigned == newUnassigned && |
| first.writeCaptured == newWriteCaptured) { |
| return first; |
| } else if (identical(second.promotedTypes, newPromotedTypes) && |
| identical(second.tested, newTested) && |
| second.assigned == newAssigned && |
| second.unassigned == newUnassigned && |
| second.writeCaptured == newWriteCaptured) { |
| return second; |
| } else { |
| return new VariableModel<Variable, Type>(newPromotedTypes, newTested, |
| newAssigned, newUnassigned, newWriteCaptured); |
| } |
| } |
| |
| static bool _typeListContains<Variable, Type>( |
| TypeOperations<Variable, Type> typeOperations, |
| List<Type> list, |
| Type searchType) { |
| for (Type type in list) { |
| if (typeOperations.isSameType(type, searchType)) return true; |
| } |
| return false; |
| } |
| } |
| |
| /// [_FlowContext] representing an assert statement or assert initializer. |
| class _AssertContext<Variable, Type> extends _SimpleContext<Variable, Type> { |
| /// Flow models associated with the condition being asserted. |
| ExpressionInfo<Variable, Type> _conditionInfo; |
| |
| _AssertContext(FlowModel<Variable, Type> previous) : super(previous); |
| |
| @override |
| String toString() => |
| '_AssertContext(previous: $_previous, conditionInfo: $_conditionInfo)'; |
| } |
| |
| /// [_FlowContext] representing a language construct that branches on a boolean |
| /// condition, such as an `if` statement, conditional expression, or a logical |
| /// binary operator. |
| class _BranchContext<Variable, Type> extends _FlowContext { |
| /// Flow models associated with the condition being branched on. |
| final ExpressionInfo<Variable, Type> _conditionInfo; |
| |
| _BranchContext(this._conditionInfo); |
| |
| @override |
| String toString() => '_BranchContext(conditionInfo: $_conditionInfo)'; |
| } |
| |
| /// [_FlowContext] representing a language construct that can be targeted by |
| /// `break` or `continue` statements, such as a loop or switch statement. |
| class _BranchTargetContext<Variable, Type> extends _FlowContext { |
| /// Accumulated flow model for all `break` statements seen so far, or `null` |
| /// if no `break` statements have been seen yet. |
| FlowModel<Variable, Type> _breakModel; |
| |
| /// Accumulated flow model for all `continue` statements seen so far, or |
| /// `null` if no `continue` statements have been seen yet. |
| FlowModel<Variable, Type> _continueModel; |
| |
| @override |
| String toString() => '_BranchTargetContext(breakModel: $_breakModel, ' |
| 'continueModel: $_continueModel)'; |
| } |
| |
| /// [_FlowContext] representing a conditional expression. |
| class _ConditionalContext<Variable, Type> |
| extends _BranchContext<Variable, Type> { |
| /// Flow models associated with the value of the conditional expression in the |
| /// circumstance where the "then" branch is taken. |
| ExpressionInfo<Variable, Type> _thenInfo; |
| |
| _ConditionalContext(ExpressionInfo<Variable, Type> conditionInfo) |
| : super(conditionInfo); |
| |
| @override |
| String toString() => '_ConditionalContext(conditionInfo: $_conditionInfo, ' |
| 'thenInfo: $_thenInfo)'; |
| } |
| |
| class _FlowAnalysisImpl<Node, Statement extends Node, Expression, Variable, |
| Type> implements FlowAnalysis<Node, Statement, Expression, Variable, Type> { |
| /// The [TypeOperations], used to access types, and check subtyping. |
| final TypeOperations<Variable, Type> typeOperations; |
| |
| /// Stack of [_FlowContext] objects representing the statements and |
| /// expressions that are currently being visited. |
| final List<_FlowContext> _stack = []; |
| |
| /// The mapping from [Statement]s that can act as targets for `break` and |
| /// `continue` statements (i.e. loops and switch statements) to the to their |
| /// context information. |
| final Map<Statement, _BranchTargetContext<Variable, Type>> |
| _statementToContext = {}; |
| |
| FlowModel<Variable, Type> _current; |
| |
| /// The most recently visited expression for which an [ExpressionInfo] object |
| /// exists, or `null` if no expression has been visited that has a |
| /// corresponding [ExpressionInfo] object. |
| Expression _expressionWithInfo; |
| |
| /// If [_expressionWithInfo] is not `null`, the [ExpressionInfo] object |
| /// corresponding to it. Otherwise `null`. |
| ExpressionInfo<Variable, Type> _expressionInfo; |
| |
| int _functionNestingLevel = 0; |
| |
| final AssignedVariables<Node, Variable> _assignedVariables; |
| |
| _FlowAnalysisImpl(this.typeOperations, this._assignedVariables) { |
| _current = new FlowModel<Variable, Type>(true); |
| } |
| |
| @override |
| bool get isReachable => _current.reachable; |
| |
| @override |
| void asExpression_end(Expression subExpression, Type type) { |
| ExpressionInfo<Variable, Type> subExpressionInfo = |
| _getExpressionInfo(subExpression); |
| Variable variable; |
| if (subExpressionInfo is _VariableReadInfo<Variable, Type>) { |
| variable = subExpressionInfo._variable; |
| } else { |
| return; |
| } |
| _current = _current.tryPromoteForTypeCast(typeOperations, variable, type); |
| } |
| |
| @override |
| void assert_afterCondition(Expression condition) { |
| _AssertContext<Variable, Type> context = |
| _stack.last as _AssertContext<Variable, Type>; |
| ExpressionInfo<Variable, Type> conditionInfo = _expressionEnd(condition); |
| context._conditionInfo = conditionInfo; |
| _current = conditionInfo.ifFalse; |
| } |
| |
| @override |
| void assert_begin() { |
| _stack.add(new _AssertContext<Variable, Type>(_current)); |
| } |
| |
| @override |
| void assert_end() { |
| _AssertContext<Variable, Type> context = |
| _stack.removeLast() as _AssertContext<Variable, Type>; |
| _current = _join(context._previous, context._conditionInfo.ifTrue); |
| } |
| |
| @override |
| void booleanLiteral(Expression expression, bool value) { |
| FlowModel<Variable, Type> unreachable = _current.setReachable(false); |
| _storeExpressionInfo( |
| expression, |
| value |
| ? new ExpressionInfo(_current, _current, unreachable) |
| : new ExpressionInfo(_current, unreachable, _current)); |
| } |
| |
| @override |
| void conditional_elseBegin(Expression thenExpression) { |
| _ConditionalContext<Variable, Type> context = |
| _stack.last as _ConditionalContext<Variable, Type>; |
| context._thenInfo = _expressionEnd(thenExpression); |
| _current = context._conditionInfo.ifFalse; |
| } |
| |
| @override |
| void conditional_end( |
| Expression conditionalExpression, Expression elseExpression) { |
| _ConditionalContext<Variable, Type> context = |
| _stack.removeLast() as _ConditionalContext<Variable, Type>; |
| ExpressionInfo<Variable, Type> thenInfo = context._thenInfo; |
| ExpressionInfo<Variable, Type> elseInfo = _expressionEnd(elseExpression); |
| _storeExpressionInfo( |
| conditionalExpression, |
| new ExpressionInfo( |
| _join(thenInfo.after, elseInfo.after), |
| _join(thenInfo.ifTrue, elseInfo.ifTrue), |
| _join(thenInfo.ifFalse, elseInfo.ifFalse))); |
| } |
| |
| @override |
| void conditional_thenBegin(Expression condition) { |
| ExpressionInfo<Variable, Type> conditionInfo = _expressionEnd(condition); |
| _stack.add(new _ConditionalContext(conditionInfo)); |
| _current = conditionInfo.ifTrue; |
| } |
| |
| @override |
| void declare(Variable variable, bool initialized) { |
| _current = _current.declare(variable, initialized); |
| } |
| |
| @override |
| void doStatement_bodyBegin(Statement doStatement) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(doStatement); |
| _BranchTargetContext<Variable, Type> context = |
| new _BranchTargetContext<Variable, Type>(); |
| _stack.add(context); |
| _current = _current.removePromotedAll(info._written, info._captured); |
| _statementToContext[doStatement] = context; |
| } |
| |
| @override |
| void doStatement_conditionBegin() { |
| _BranchTargetContext<Variable, Type> context = |
| _stack.last as _BranchTargetContext<Variable, Type>; |
| _current = _join(_current, context._continueModel); |
| } |
| |
| @override |
| void doStatement_end(Expression condition) { |
| _BranchTargetContext<Variable, Type> context = |
| _stack.removeLast() as _BranchTargetContext<Variable, Type>; |
| _current = _join(_expressionEnd(condition).ifFalse, context._breakModel); |
| } |
| |
| @override |
| void equalityOp_end(Expression wholeExpression, Expression rightOperand, |
| {bool notEqual = false}) { |
| _BranchContext<Variable, Type> context = |
| _stack.removeLast() as _BranchContext<Variable, Type>; |
| ExpressionInfo<Variable, Type> lhsInfo = context._conditionInfo; |
| ExpressionInfo<Variable, Type> rhsInfo = _getExpressionInfo(rightOperand); |
| Variable variable; |
| if (lhsInfo is _NullInfo<Variable, Type> && |
| rhsInfo is _VariableReadInfo<Variable, Type>) { |
| variable = rhsInfo._variable; |
| } else if (rhsInfo is _NullInfo<Variable, Type> && |
| lhsInfo is _VariableReadInfo<Variable, Type>) { |
| variable = lhsInfo._variable; |
| } else { |
| return; |
| } |
| ExpressionInfo<Variable, Type> expressionInfo = |
| _current.tryMarkNonNullable(typeOperations, variable); |
| _storeExpressionInfo(wholeExpression, |
| notEqual ? expressionInfo : ExpressionInfo.invert(expressionInfo)); |
| } |
| |
| @override |
| void equalityOp_rightBegin(Expression leftOperand) { |
| _stack.add( |
| new _BranchContext<Variable, Type>(_getExpressionInfo(leftOperand))); |
| } |
| |
| @override |
| void finish() { |
| assert(_stack.isEmpty); |
| } |
| |
| @override |
| void for_bodyBegin(Statement node, Expression condition) { |
| ExpressionInfo<Variable, Type> conditionInfo = condition == null |
| ? new ExpressionInfo(_current, _current, _current.setReachable(false)) |
| : _expressionEnd(condition); |
| _WhileContext<Variable, Type> context = |
| new _WhileContext<Variable, Type>(conditionInfo); |
| _stack.add(context); |
| if (node != null) { |
| _statementToContext[node] = context; |
| } |
| _current = conditionInfo.ifTrue; |
| } |
| |
| @override |
| void for_conditionBegin(Node node) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(node); |
| _current = _current.removePromotedAll(info._written, info._captured); |
| } |
| |
| @override |
| void for_end() { |
| FlowModel<Variable, Type> afterUpdate = _current; |
| |
| _WhileContext<Variable, Type> context = |
| _stack.removeLast() as _WhileContext<Variable, Type>; |
| // Tail of the stack: falseCondition, break |
| FlowModel<Variable, Type> breakState = context._breakModel; |
| FlowModel<Variable, Type> falseCondition = context._conditionInfo.ifFalse; |
| |
| _current = _join(falseCondition, breakState); |
| _current = _current.joinUnassigned(other: afterUpdate); |
| } |
| |
| @override |
| void for_updaterBegin() { |
| _WhileContext<Variable, Type> context = |
| _stack.last as _WhileContext<Variable, Type>; |
| _current = _join(_current, context._continueModel); |
| } |
| |
| @override |
| void forEach_bodyBegin(Node node, Variable loopVariable, Type writtenType) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(node); |
| _SimpleStatementContext<Variable, Type> context = |
| new _SimpleStatementContext<Variable, Type>(_current); |
| _stack.add(context); |
| _current = _current.removePromotedAll(info._written, info._captured); |
| if (loopVariable != null) { |
| _current = _current.write(loopVariable, writtenType, typeOperations); |
| } |
| } |
| |
| @override |
| void forEach_end() { |
| _SimpleStatementContext<Variable, Type> context = |
| _stack.removeLast() as _SimpleStatementContext<Variable, Type>; |
| _current = _join(_current, context._previous); |
| } |
| |
| @override |
| void functionExpression_begin(Node node) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(node); |
| ++_functionNestingLevel; |
| _current = _current.removePromotedAll(const [], info._written); |
| _stack.add(new _SimpleContext(_current)); |
| _current = _current.removePromotedAll(_assignedVariables._anywhere._written, |
| _assignedVariables._anywhere._captured); |
| _current = _current.joinUnassigned( |
| written: _assignedVariables._anywhere._written, |
| ); |
| } |
| |
| @override |
| void functionExpression_end() { |
| --_functionNestingLevel; |
| assert(_functionNestingLevel >= 0); |
| FlowModel<Variable, Type> afterBody = _current; |
| _SimpleContext<Variable, Type> context = |
| _stack.removeLast() as _SimpleContext<Variable, Type>; |
| _current = context._previous; |
| _current = _current.joinUnassigned(other: afterBody); |
| } |
| |
| @override |
| void handleBreak(Statement target) { |
| _BranchTargetContext<Variable, Type> context = _statementToContext[target]; |
| if (context != null) { |
| context._breakModel = _join(context._breakModel, _current); |
| } |
| _current = _current.setReachable(false); |
| } |
| |
| @override |
| void handleContinue(Statement target) { |
| _BranchTargetContext<Variable, Type> context = _statementToContext[target]; |
| if (context != null) { |
| context._continueModel = _join(context._continueModel, _current); |
| } |
| _current = _current.setReachable(false); |
| } |
| |
| @override |
| void handleExit() { |
| _current = _current.setReachable(false); |
| } |
| |
| @override |
| void ifNullExpression_end() { |
| _SimpleContext<Variable, Type> context = |
| _stack.removeLast() as _SimpleContext<Variable, Type>; |
| _current = _join(_current, context._previous); |
| } |
| |
| @override |
| void ifNullExpression_rightBegin(Expression leftHandSide) { |
| ExpressionInfo<Variable, Type> lhsInfo = _getExpressionInfo(leftHandSide); |
| FlowModel<Variable, Type> promoted; |
| if (lhsInfo is _VariableReadInfo<Variable, Type>) { |
| ExpressionInfo<Variable, Type> promotionInfo = |
| _current.tryMarkNonNullable(typeOperations, lhsInfo._variable); |
| _current = promotionInfo.ifFalse; |
| promoted = promotionInfo.ifTrue; |
| } else { |
| promoted = _current; |
| } |
| _stack.add(new _SimpleContext<Variable, Type>(promoted)); |
| } |
| |
| @override |
| void ifStatement_elseBegin() { |
| _IfContext<Variable, Type> context = |
| _stack.last as _IfContext<Variable, Type>; |
| context._afterThen = _current; |
| _current = context._conditionInfo.ifFalse; |
| } |
| |
| @override |
| void ifStatement_end(bool hasElse) { |
| _IfContext<Variable, Type> context = |
| _stack.removeLast() as _IfContext<Variable, Type>; |
| FlowModel<Variable, Type> afterThen; |
| FlowModel<Variable, Type> afterElse; |
| if (hasElse) { |
| afterThen = context._afterThen; |
| afterElse = _current; |
| } else { |
| afterThen = _current; // no `else`, so `then` is still current |
| afterElse = context._conditionInfo.ifFalse; |
| } |
| _current = _join(afterThen, afterElse); |
| } |
| |
| @override |
| void ifStatement_thenBegin(Expression condition) { |
| ExpressionInfo<Variable, Type> conditionInfo = _expressionEnd(condition); |
| _stack.add(new _IfContext(conditionInfo)); |
| _current = conditionInfo.ifTrue; |
| } |
| |
| @override |
| bool isAssigned(Variable variable) { |
| return _current.infoFor(variable).assigned; |
| } |
| |
| @override |
| void isExpression_end(Expression isExpression, Expression subExpression, |
| bool isNot, Type type) { |
| ExpressionInfo<Variable, Type> subExpressionInfo = |
| _getExpressionInfo(subExpression); |
| Variable variable; |
| if (subExpressionInfo is _VariableReadInfo<Variable, Type>) { |
| variable = subExpressionInfo._variable; |
| } else { |
| return; |
| } |
| ExpressionInfo<Variable, Type> expressionInfo = |
| _current.tryPromoteForTypeCheck(typeOperations, variable, type); |
| _storeExpressionInfo(isExpression, |
| isNot ? ExpressionInfo.invert(expressionInfo) : expressionInfo); |
| } |
| |
| @override |
| bool isUnassigned(Variable variable) { |
| return _current.infoFor(variable).unassigned; |
| } |
| |
| @override |
| void labeledStatement_begin(Node node) { |
| _BranchTargetContext<Variable, Type> context = |
| new _BranchTargetContext<Variable, Type>(); |
| _stack.add(context); |
| _statementToContext[node] = context; |
| } |
| |
| @override |
| void labeledStatement_end() { |
| _BranchTargetContext<Variable, Type> context = |
| _stack.removeLast() as _BranchTargetContext<Variable, Type>; |
| _current = _join(_current, context._breakModel); |
| } |
| |
| @override |
| void logicalBinaryOp_end(Expression wholeExpression, Expression rightOperand, |
| {@required bool isAnd}) { |
| _BranchContext<Variable, Type> context = |
| _stack.removeLast() as _BranchContext<Variable, Type>; |
| ExpressionInfo<Variable, Type> rhsInfo = _expressionEnd(rightOperand); |
| |
| FlowModel<Variable, Type> trueResult; |
| FlowModel<Variable, Type> falseResult; |
| if (isAnd) { |
| trueResult = rhsInfo.ifTrue; |
| falseResult = _join(context._conditionInfo.ifFalse, rhsInfo.ifFalse); |
| } else { |
| trueResult = _join(context._conditionInfo.ifTrue, rhsInfo.ifTrue); |
| falseResult = rhsInfo.ifFalse; |
| } |
| _storeExpressionInfo( |
| wholeExpression, |
| new ExpressionInfo( |
| _join(trueResult, falseResult), trueResult, falseResult)); |
| } |
| |
| @override |
| void logicalBinaryOp_rightBegin(Expression leftOperand, |
| {@required bool isAnd}) { |
| ExpressionInfo<Variable, Type> conditionInfo = _expressionEnd(leftOperand); |
| _stack.add(new _BranchContext<Variable, Type>(conditionInfo)); |
| _current = isAnd ? conditionInfo.ifTrue : conditionInfo.ifFalse; |
| } |
| |
| @override |
| void logicalNot_end(Expression notExpression, Expression operand) { |
| ExpressionInfo<Variable, Type> conditionInfo = _expressionEnd(operand); |
| _storeExpressionInfo(notExpression, ExpressionInfo.invert(conditionInfo)); |
| } |
| |
| @override |
| void nonNullAssert_end(Expression operand) { |
| ExpressionInfo<Variable, Type> operandInfo = _getExpressionInfo(operand); |
| if (operandInfo is _VariableReadInfo<Variable, Type>) { |
| _current = _current |
| .tryMarkNonNullable(typeOperations, operandInfo._variable) |
| .ifTrue; |
| } |
| } |
| |
| @override |
| void nullAwareAccess_end() { |
| _SimpleContext<Variable, Type> context = |
| _stack.removeLast() as _SimpleContext<Variable, Type>; |
| _current = _join(_current, context._previous); |
| } |
| |
| @override |
| void nullAwareAccess_rightBegin(Expression target) { |
| _stack.add(new _SimpleContext<Variable, Type>(_current)); |
| if (target != null) { |
| ExpressionInfo<Variable, Type> targetInfo = _getExpressionInfo(target); |
| if (targetInfo is _VariableReadInfo<Variable, Type>) { |
| _current = _current |
| .tryMarkNonNullable(typeOperations, targetInfo._variable) |
| .ifTrue; |
| } |
| } |
| } |
| |
| @override |
| void nullLiteral(Expression expression) { |
| _storeExpressionInfo(expression, new _NullInfo(_current)); |
| } |
| |
| @override |
| void parenthesizedExpression( |
| Expression outerExpression, Expression innerExpression) { |
| if (identical(_expressionWithInfo, innerExpression)) { |
| _expressionWithInfo = outerExpression; |
| } |
| } |
| |
| @override |
| Type promotedType(Variable variable) { |
| return _current.infoFor(variable).promotedTypes?.last; |
| } |
| |
| @override |
| void switchStatement_beginCase(bool hasLabel, Node node) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(node); |
| _SimpleStatementContext<Variable, Type> context = |
| _stack.last as _SimpleStatementContext<Variable, Type>; |
| if (hasLabel) { |
| _current = |
| context._previous.removePromotedAll(info._written, info._captured); |
| } else { |
| _current = context._previous; |
| } |
| } |
| |
| @override |
| void switchStatement_end(bool isExhaustive) { |
| _SimpleStatementContext<Variable, Type> context = |
| _stack.removeLast() as _SimpleStatementContext<Variable, Type>; |
| FlowModel<Variable, Type> breakState = context._breakModel; |
| |
| // It is allowed to "fall off" the end of a switch statement, so join the |
| // current state to any breaks that were found previously. |
| breakState = _join(breakState, _current); |
| |
| // And, if there is an implicit fall-through default, join it to any breaks. |
| if (!isExhaustive) breakState = _join(breakState, context._previous); |
| |
| _current = breakState; |
| } |
| |
| @override |
| void switchStatement_expressionEnd(Statement switchStatement) { |
| _SimpleStatementContext<Variable, Type> context = |
| new _SimpleStatementContext<Variable, Type>(_current); |
| _stack.add(context); |
| _statementToContext[switchStatement] = context; |
| } |
| |
| @override |
| void tryCatchStatement_bodyBegin() { |
| _stack.add(new _TryContext<Variable, Type>(_current)); |
| } |
| |
| @override |
| void tryCatchStatement_bodyEnd(Node body) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(body); |
| _TryContext<Variable, Type> context = |
| _stack.last as _TryContext<Variable, Type>; |
| FlowModel<Variable, Type> beforeBody = context._previous; |
| FlowModel<Variable, Type> beforeCatch = |
| beforeBody.removePromotedAll(info._written, info._captured); |
| context._beforeCatch = beforeCatch; |
| context._afterBodyAndCatches = _current; |
| } |
| |
| @override |
| void tryCatchStatement_catchBegin( |
| Variable exceptionVariable, Variable stackTraceVariable) { |
| _TryContext<Variable, Type> context = |
| _stack.last as _TryContext<Variable, Type>; |
| _current = context._beforeCatch; |
| if (exceptionVariable != null) { |
| _current = _current.declare(exceptionVariable, true); |
| } |
| if (stackTraceVariable != null) { |
| _current = _current.declare(stackTraceVariable, true); |
| } |
| } |
| |
| @override |
| void tryCatchStatement_catchEnd() { |
| _TryContext<Variable, Type> context = |
| _stack.last as _TryContext<Variable, Type>; |
| context._afterBodyAndCatches = |
| _join(context._afterBodyAndCatches, _current); |
| } |
| |
| @override |
| void tryCatchStatement_end() { |
| _TryContext<Variable, Type> context = |
| _stack.removeLast() as _TryContext<Variable, Type>; |
| _current = context._afterBodyAndCatches; |
| } |
| |
| @override |
| void tryFinallyStatement_bodyBegin() { |
| _stack.add(new _TryContext<Variable, Type>(_current)); |
| } |
| |
| @override |
| void tryFinallyStatement_end(Node finallyBlock) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(finallyBlock); |
| _TryContext<Variable, Type> context = |
| _stack.removeLast() as _TryContext<Variable, Type>; |
| _current = _current.restrict( |
| typeOperations, context._afterBodyAndCatches, info._written); |
| } |
| |
| @override |
| void tryFinallyStatement_finallyBegin(Node body) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(body); |
| _TryContext<Variable, Type> context = |
| _stack.last as _TryContext<Variable, Type>; |
| context._afterBodyAndCatches = _current; |
| _current = _join(_current, |
| context._previous.removePromotedAll(info._written, info._captured)); |
| } |
| |
| @override |
| Type variableRead(Expression expression, Variable variable) { |
| _storeExpressionInfo(expression, new _VariableReadInfo(_current, variable)); |
| return _current.infoFor(variable).promotedTypes?.last; |
| } |
| |
| @override |
| void whileStatement_bodyBegin( |
| Statement whileStatement, Expression condition) { |
| ExpressionInfo<Variable, Type> conditionInfo = _expressionEnd(condition); |
| _WhileContext<Variable, Type> context = |
| new _WhileContext<Variable, Type>(conditionInfo); |
| _stack.add(context); |
| _statementToContext[whileStatement] = context; |
| _current = conditionInfo.ifTrue; |
| } |
| |
| @override |
| void whileStatement_conditionBegin(Node node) { |
| AssignedVariablesNodeInfo<Variable> info = |
| _assignedVariables._getInfoForNode(node); |
| _current = _current.removePromotedAll(info._written, info._captured); |
| } |
| |
| @override |
| void whileStatement_end() { |
| _WhileContext<Variable, Type> context = |
| _stack.removeLast() as _WhileContext<Variable, Type>; |
| var afterBody = _current; |
| _current = _join(context._conditionInfo.ifFalse, context._breakModel); |
| _current = _current.joinUnassigned(other: afterBody); |
| } |
| |
| @override |
| void write(Variable variable, Type writtenType) { |
| assert( |
| _assignedVariables._anywhere._written.contains(variable), |
| "Variable is written to, but was not included in " |
| "_variablesWrittenAnywhere: $variable"); |
| _current = _current.write(variable, writtenType, typeOperations); |
| } |
| |
| void _dumpState() { |
| print(' current: $_current'); |
| print(' expressionWithInfo: $_expressionWithInfo'); |
| print(' expressionInfo: $_expressionInfo'); |
| print(' stack:'); |
| for (_FlowContext stackEntry in _stack.reversed) { |
| print(' $stackEntry'); |
| } |
| } |
| |
| /// Gets the [ExpressionInfo] associated with the [expression] (which should |
| /// be the last expression that was traversed). If there is no |
| /// [ExpressionInfo] associated with the [expression], then a fresh |
| /// [ExpressionInfo] is created recording the current flow analysis state. |
| ExpressionInfo<Variable, Type> _expressionEnd(Expression expression) => |
| _getExpressionInfo(expression) ?? |
| new ExpressionInfo(_current, _current, _current); |
| |
| /// Gets the [ExpressionInfo] associated with the [expression] (which should |
| /// be the last expression that was traversed). If there is no |
| /// [ExpressionInfo] associated with the [expression], then `null` is |
| /// returned. |
| ExpressionInfo<Variable, Type> _getExpressionInfo(Expression expression) { |
| if (identical(expression, _expressionWithInfo)) { |
| ExpressionInfo<Variable, Type> expressionInfo = _expressionInfo; |
| _expressionInfo = null; |
| return expressionInfo; |
| } else { |
| return null; |
| } |
| } |
| |
| FlowModel<Variable, Type> _join( |
| FlowModel<Variable, Type> first, FlowModel<Variable, Type> second) => |
| FlowModel.join(typeOperations, first, second, _current._emptyVariableMap); |
| |
| /// Associates [expression], which should be the most recently visited |
| /// expression, with the given [expressionInfo] object, and updates the |
| /// current flow model state to correspond to it. |
| void _storeExpressionInfo( |
| Expression expression, ExpressionInfo<Variable, Type> expressionInfo) { |
| _expressionWithInfo = expression; |
| _expressionInfo = expressionInfo; |
| _current = expressionInfo.after; |
| } |
| } |
| |
| /// Base class for objects representing constructs in the Dart programming |
| /// language for which flow analysis information needs to be tracked. |
| abstract class _FlowContext {} |
| |
| /// [_FlowContext] representing an `if` statement. |
| class _IfContext<Variable, Type> extends _BranchContext<Variable, Type> { |
| /// Flow model associated with the state of program execution after the `if` |
| /// statement executes, in the circumstance where the "then" branch is taken. |
| FlowModel<Variable, Type> _afterThen; |
| |
| _IfContext(ExpressionInfo<Variable, Type> conditionInfo) |
| : super(conditionInfo); |
| |
| @override |
| String toString() => |
| '_IfContext(conditionInfo: $_conditionInfo, afterThen: $_afterThen)'; |
| } |
| |
| /// [ExpressionInfo] representing a `null` literal. |
| class _NullInfo<Variable, Type> implements ExpressionInfo<Variable, Type> { |
| @override |
| final FlowModel<Variable, Type> after; |
| |
| _NullInfo(this.after); |
| |
| @override |
| FlowModel<Variable, Type> get ifFalse => after; |
| |
| @override |
| FlowModel<Variable, Type> get ifTrue => after; |
| } |
| |
| /// [_FlowContext] representing a language construct for which flow analysis |
| /// must store a flow model state to be retrieved later, such as a `try` |
| /// statement, function expression, or "if-null" (`??`) expression. |
| class _SimpleContext<Variable, Type> extends _FlowContext { |
| /// The stored state. For a `try` statement, this is the state from the |
| /// beginning of the `try` block. For a function expression, this is the |
| /// state at the point the function expression was created. For an "if-null" |
| /// expression, this is the state after execution of the expression before the |
| /// `??`. |
| final FlowModel<Variable, Type> _previous; |
| |
| _SimpleContext(this._previous); |
| |
| @override |
| String toString() => '_SimpleContext(previous: $_previous)'; |
| } |
| |
| /// [_FlowContext] representing a language construct that can be targeted by |
| /// `break` or `continue` statements, and for which flow analysis must store a |
| /// flow model state to be retrieved later. Examples include "for each" and |
| /// `switch` statements. |
| class _SimpleStatementContext<Variable, Type> |
| extends _BranchTargetContext<Variable, Type> { |
| /// The stored state. For a "for each" statement, this is the state after |
| /// evaluation of the iterable. For a `switch` statement, this is the state |
| /// after evaluation of the switch expression. |
| final FlowModel<Variable, Type> _previous; |
| |
| _SimpleStatementContext(this._previous); |
| |
| @override |
| String toString() => '_SimpleStatementContext(breakModel: $_breakModel, ' |
| 'continueModel: $_continueModel, previous: $_previous)'; |
| } |
| |
| /// [_FlowContext] representing a try statement. |
| class _TryContext<Variable, Type> extends _SimpleContext<Variable, Type> { |
| /// If the statement is a "try/catch" statement, the flow model representing |
| /// program state at the top of any `catch` block. |
| FlowModel<Variable, Type> _beforeCatch; |
| |
| /// If the statement is a "try/catch" statement, the accumulated flow model |
| /// representing program state after the `try` block or one of the `catch` |
| /// blocks has finished executing. If the statement is a "try/finally" |
| /// statement, the flow model representing program state after the `try` block |
| /// has finished executing. |
| FlowModel<Variable, Type> _afterBodyAndCatches; |
| |
| _TryContext(FlowModel<Variable, Type> previous) : super(previous); |
| |
| @override |
| String toString() => |
| '_TryContext(previous: $_previous, beforeCatch: $_beforeCatch, ' |
| 'afterBodyAndCatches: $_afterBodyAndCatches)'; |
| } |
| |
| /// [ExpressionInfo] representing an expression that reads the value of a |
| /// variable. |
| class _VariableReadInfo<Variable, Type> |
| implements ExpressionInfo<Variable, Type> { |
| @override |
| final FlowModel<Variable, Type> after; |
| |
| /// The variable that is being read. |
| final Variable _variable; |
| |
| _VariableReadInfo(this.after, this._variable); |
| |
| @override |
| FlowModel<Variable, Type> get ifFalse => after; |
| |
| @override |
| FlowModel<Variable, Type> get ifTrue => after; |
| |
| @override |
| String toString() => '_VariableReadInfo(after: $after, variable: $_variable)'; |
| } |
| |
| /// [_FlowContext] representing a `while` loop (or a C-style `for` loop, which |
| /// is functionally similar). |
| class _WhileContext<Variable, Type> |
| extends _BranchTargetContext<Variable, Type> { |
| /// Flow models associated with the loop condition. |
| final ExpressionInfo<Variable, Type> _conditionInfo; |
| |
| _WhileContext(this._conditionInfo); |
| |
| @override |
| String toString() => '_WhileContext(breakModel: $_breakModel, ' |
| 'continueModel: $_continueModel, conditionInfo: $_conditionInfo)'; |
| } |