pkg/dev_compiler/lib/src/analyzer/element_helpers.dart

// Copyright (c) 2016, 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 'dart:collection';

/// Helpers for Analyzer's Element model and corelib model.

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/type.dart'
    show DartType, InterfaceType, ParameterizedType, FunctionType;
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/generated/constant.dart'
    show DartObject, DartObjectImpl;

class Tuple2<T0, T1> {
  final T0 e0;
  final T1 e1;
  Tuple2(this.e0, this.e1);
}

// TODO(jmesserly): replace this with instantiateToBounds
T fillDynamicTypeArgs<T extends DartType>(T t) {
  if (t is ParameterizedType && t.typeArguments.isNotEmpty) {
    var rawT = (t.element as TypeParameterizedElement).type;
    var dyn =
        new List.filled(rawT.typeArguments.length, DynamicTypeImpl.instance);
    return rawT.substitute2(dyn, rawT.typeArguments) as T;
  }
  return t;
}

/// Given an annotated [node] and a [test] function, returns the first matching
/// constant valued annotation.
///
/// For example if we had the ClassDeclaration node for `FontElement`:
///
///    @js.JS('HTMLFontElement')
///    @deprecated
///    class FontElement { ... }
///
/// We could match `@deprecated` with a test function like:
///
///    (v) => v.type.name == 'Deprecated' && v.type.element.library.isDartCore
///
DartObject findAnnotation(Element element, bool test(DartObjectImpl value)) {
  for (var metadata in element.metadata) {
    var value = metadata.computeConstantValue();
    if (value is DartObjectImpl && test(value)) return value;
  }
  return null;
}

/// Searches all supertype, in order of most derived members, to see if any
/// [match] a condition. If so, returns the first match, otherwise returns null.
InterfaceType findSupertype(InterfaceType type, bool match(InterfaceType t)) {
  for (var m in type.mixins.reversed) {
    if (match(m)) return m;
  }
  var s = type.superclass;
  if (s == null) return null;

  if (match(s)) return type;
  return findSupertype(s, match);
}

//TODO(leafp): Is this really necessary?  In theory I think
// the static type should always be filled in for resolved
// ASTs.  This may be a vestigial workaround.
DartType getStaticType(Expression e) =>
    e.staticType ?? DynamicTypeImpl.instance;

// TODO(leafp) Factor this out or use an existing library
/// Similar to [SimpleIdentifier] inGetterContext, inSetterContext, and
/// inDeclarationContext, this method returns true if [node] is used in an
/// invocation context such as a MethodInvocation.
bool inInvocationContext(Expression node) {
  if (node == null) return false;
  var parent = node.parent;
  while (parent is ParenthesizedExpression) {
    node = parent;
    parent = node.parent;
  }
  return parent is InvocationExpression && identical(node, parent.function) ||
      parent is MethodInvocation &&
          parent.methodName.name == 'call' &&
          identical(node, parent.target);
}

bool isInlineJS(Element e) {
  if (e != null && e.name == 'JS' && e is FunctionElement) {
    var uri = e.librarySource.uri;
    return uri.scheme == 'dart' && uri.path == '_foreign_helper';
  }
  return false;
}

bool isLibraryPrefix(Expression node) =>
    node is SimpleIdentifier && node.staticElement is PrefixElement;

ExecutableElement getFunctionBodyElement(FunctionBody body) {
  var f = body.parent;
  if (f is FunctionExpression) {
    return f.element;
  } else if (f is MethodDeclaration) {
    return f.element;
  } else {
    return (f as ConstructorDeclaration).element;
  }
}

/// Returns the value of the `name` field from the [match]ing annotation on
/// [element], or `null` if we didn't find a valid match or it was not a string.
///
/// For example, consider this code:
///
///     class MyAnnotation {
///       final String name;
///       // ...
///       const MyAnnotation(this.name/*, ... other params ... */);
///     }
///
///     @MyAnnotation('FooBar')
///     main() { ... }
///
/// If we match the annotation for the `@MyAnnotation('FooBar')` this will
/// return the string 'FooBar'.
String getAnnotationName(Element element, bool match(DartObjectImpl value)) =>
    findAnnotation(element, match)?.getField('name')?.toStringValue();

List<ClassElement> getSuperclasses(ClassElement cls) {
  var result = <ClassElement>[];
  var visited = new HashSet<ClassElement>();
  while (cls != null && visited.add(cls)) {
    for (var mixinType in cls.mixins.reversed) {
      var mixin = mixinType.element;
      if (mixin != null) result.add(mixin);
    }
    var supertype = cls.supertype;
    if (supertype == null) break;

    cls = supertype.element;
    result.add(cls);
  }
  return result;
}

List<ClassElement> getImmediateSuperclasses(ClassElement c) {
  var result = <ClassElement>[];
  for (var m in c.mixins.reversed) {
    result.add(m.element);
  }
  var s = c.supertype;
  if (s != null) result.add(s.element);
  return result;
}

/// Returns true if the library [l] is dart:_runtime.
// TODO(jmesserly): unlike other methods in this file, this one wouldn't be
// suitable for upstream to Analyzer, as it's DDC specific.
bool isSdkInternalRuntime(LibraryElement l) {
  var uri = l.source.uri;
  return uri.scheme == 'dart' && uri.path == '_runtime';
}

/// Return `true` if the given [classElement] has a noSuchMethod() method
/// distinct from the one declared in class Object, as per the Dart Language
/// Specification (section 10.4).
// TODO(jmesserly): this was taken from error_verifier.dart
bool hasNoSuchMethod(ClassElement classElement) {
  // TODO(jmesserly): this is slow in Analyzer. It's a linear scan through all
  // methods, up through the class hierarchy.
  var method = classElement.lookUpMethod(
      FunctionElement.NO_SUCH_METHOD_METHOD_NAME, classElement.library);
  var definingClass = method?.enclosingElement;
  return definingClass != null && !definingClass.type.isObject;
}

/// Returns true if this class is of the form:
/// `class C = Object with M [implements I1, I2 ...];`
///
/// A mixin alias class is a mixin application, that can also be itself used as
/// a mixin.
bool isMixinAliasClass(ClassElement c) {
  return c.isMixinApplication && c.supertype.isObject && c.mixins.length == 1;
}

bool isCallableClass(ClassElement c) {
  // See if we have a "call" with a statically known function type:
  //
  // - if it's a method, then it does because all methods do,
  // - if it's a getter, check the return type.
  //
  // Other cases like a getter returning dynamic/Object/Function will be
  // handled at runtime by the dynamic call mechanism. So we only
  // concern ourselves with statically known function types.
  //
  // We can ignore `noSuchMethod` because:
  // * `dynamic d; d();` without a declared `call` method is handled by dcall.
  // * for `class C implements Callable { noSuchMethod(i) { ... } }` we find
  //   the `call` method on the `Callable` interface.
  var callMethod = c.type.lookUpInheritedGetterOrMethod('call');
  return callMethod is PropertyAccessorElement
      ? callMethod.returnType is FunctionType
      : callMethod != null;
}

/// Returns true if [x] and [y] are equal, in other words, `x <: y` and `y <: x`
/// and they have equivalent display form when printed.
//
// TODO(jmesserly): this exists to work around broken FunctionTypeImpl.== in
// Analyzer. It has two bugs:
// - typeArguments are considered, even though this has no semantic effect.
//   For example: `int -> int` that resulted from `(<T>(T) -> T)<int>` will not
//   equal another `int -> int`, even though they are the same type.
// - named arguments are incorrectly treated as ordered, see
//   https://github.com/dart-lang/sdk/issues/26126.
bool typesAreEqual(DartType x, DartType y) {
  if (identical(x, y)) return true;
  if (x is FunctionType) {
    if (y is FunctionType) {
      if (x.typeFormals.length != y.typeFormals.length) {
        return false;
      }
      // `<T>T -> T` should be equal to `<U>U -> U`
      // To test this, we instantiate both types with the same (unique) type
      // variables, and see if the result is equal.
      if (x.typeFormals.isNotEmpty) {
        var fresh = FunctionTypeImpl.relateTypeFormals(
            x, y, (t, s, _, __) => typesAreEqual(t, s));
        if (fresh == null) return false;
        return typesAreEqual(x.instantiate(fresh), y.instantiate(fresh));
      }

      return typesAreEqual(x.returnType, y.returnType) &&
          _argumentsAreEqual(x.normalParameterTypes, y.normalParameterTypes) &&
          _argumentsAreEqual(
              x.optionalParameterTypes, y.optionalParameterTypes) &&
          _namedArgumentsAreEqual(x.namedParameterTypes, y.namedParameterTypes);
    } else {
      return false;
    }
  }
  if (x is InterfaceType) {
    return y is InterfaceType &&
        x.element == y.element &&
        _argumentsAreEqual(x.typeArguments, y.typeArguments);
  }
  return x == y;
}

bool _argumentsAreEqual(List<DartType> first, List<DartType> second) {
  if (first.length != second.length) return false;
  for (int i = 0; i < first.length; i++) {
    if (!typesAreEqual(first[i], second[i])) return false;
  }
  return true;
}

bool _namedArgumentsAreEqual(
    Map<String, DartType> xArgs, Map<String, DartType> yArgs) {
  if (yArgs.length != xArgs.length) return false;
  for (var name in xArgs.keys) {
    var x = xArgs[name];
    var y = yArgs[name];
    if (y == null || !typesAreEqual(x, y)) return false;
  }
  return true;
}

/// Returns a valid hashCode for [t] for use with [typesAreEqual].
int typeHashCode(DartType t) {
  if (t is FunctionType) {
    // TODO(jmesserly): this is from Analyzer; it's not a great hash function.
    int code = typeHashCode(t.returnType);
    for (var p in t.normalParameterTypes) {
      code = (code << 1) + typeHashCode(p);
    }
    for (var p in t.optionalParameterTypes) {
      code = (code << 1) + typeHashCode(p);
    }
    for (var p in t.namedParameterTypes.values) {
      code ^= typeHashCode(p); // xor because named parameters are unordered.
    }
    return code;
  }
  return t.hashCode;
}

Uri uriForCompilationUnit(CompilationUnitElement unit) {
  if (unit.source.isInSystemLibrary) {
    return unit.source.uri;
  }
  // TODO(jmesserly): this needs serious cleanup.
  // There does appear to be something strange going on with Analyzer
  // URIs if we try and use them directly on Windows.
  // See also compiler.dart placeSourceMap, which could use cleanup too.
  var sourcePath = unit.source.fullName;
  return sourcePath.startsWith('package:')
      ? Uri.parse(sourcePath)
      // TODO(jmesserly): shouldn't this be path.toUri?
      : new Uri.file(sourcePath);
}

/// Returns true iff this factory constructor just throws [UnsupportedError]/
///
/// `dart:html` has many of these.
bool isUnsupportedFactoryConstructor(ConstructorDeclaration node) {
  var ctorBody = node.body;
  var element = node.element;
  if (element.isPrivate &&
      element.librarySource.isInSystemLibrary &&
      ctorBody is BlockFunctionBody) {
    var statements = ctorBody.block.statements;
    if (statements.length == 1) {
      var statement = statements[0];
      if (statement is ExpressionStatement) {
        var expr = statement.expression;
        if (expr is ThrowExpression &&
            expr.expression is InstanceCreationExpression) {
          if (expr.expression.staticType.name == 'UnsupportedError') {
            // HTML adds a lot of private constructors that are unreachable.
            // Skip these.
            return true;
          }
        }
      }
    }
  }
  return false;
}

bool isBuiltinAnnotation(
    DartObjectImpl value, String libraryName, String annotationName) {
  var e = value?.type?.element;
  if (e?.name != annotationName) return false;
  var uri = e.source.uri;
  var path = uri.pathSegments[0];
  return uri.scheme == 'dart' && path == libraryName;
}