pkg/compiler/lib/src/resolution/typedefs.dart

// Copyright (c) 2015, 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.

library dart2js.resolution.typedefs;

import '../compiler.dart' show
    Compiler;
import '../dart_types.dart';
import '../diagnostics/messages.dart' show
    MessageKind;
import '../elements/elements.dart' show
    FunctionSignature,
    TypedefElement,
    TypeVariableElement;
import '../elements/modelx.dart' show
    ErroneousElementX,
    TypedefElementX;
import '../tree/tree.dart';
import '../util/util.dart' show
    Link;

import 'class_hierarchy.dart' show
    TypeDefinitionVisitor;
import 'registry.dart' show
    ResolutionRegistry;
import 'scope.dart' show
    MethodScope,
    TypeDeclarationScope;
import 'signatures.dart' show
    SignatureResolver;

class TypedefResolverVisitor extends TypeDefinitionVisitor {
  TypedefElementX get element => enclosingElement;

  TypedefResolverVisitor(Compiler compiler,
                         TypedefElement typedefElement,
                         ResolutionRegistry registry)
      : super(compiler, typedefElement, registry);

  visitTypedef(Typedef node) {
    element.computeType(compiler);
    scope = new TypeDeclarationScope(scope, element);
    resolveTypeVariableBounds(node.typeParameters);

    FunctionSignature signature = SignatureResolver.analyze(
        compiler, node.formals, node.returnType, element, registry,
        defaultValuesError: MessageKind.TYPEDEF_FORMAL_WITH_DEFAULT);
    element.functionSignature = signature;

    scope = new MethodScope(scope, element);
    signature.forEachParameter(addToScope);

    element.alias = signature.type;

    void checkCyclicReference() {
      element.checkCyclicReference(compiler);
    }
    addDeferredAction(element, checkCyclicReference);
  }
}

// TODO(johnniwinther): Replace with a traversal on the AST when the type
// annotations in typedef alias are stored in a [TreeElements] mapping.
class TypedefCyclicVisitor extends BaseDartTypeVisitor {
  final Compiler compiler;
  final TypedefElementX element;
  bool hasCyclicReference = false;

  Link<TypedefElement> seenTypedefs = const Link<TypedefElement>();

  int seenTypedefsCount = 0;

  Link<TypeVariableElement> seenTypeVariables =
      const Link<TypeVariableElement>();

  TypedefCyclicVisitor(Compiler this.compiler, TypedefElement this.element);

  visitType(DartType type, _) {
    // Do nothing.
  }

  visitTypedefType(TypedefType type, _) {
    TypedefElementX typedefElement = type.element;
    if (seenTypedefs.contains(typedefElement)) {
      if (!hasCyclicReference && identical(element, typedefElement)) {
        // Only report an error on the checked typedef to avoid generating
        // multiple errors for the same cyclicity.
        hasCyclicReference = true;
        if (seenTypedefsCount == 1) {
          // Direct cyclicity.
          compiler.reportErrorMessage(
              element,
              MessageKind.CYCLIC_TYPEDEF,
              {'typedefName': element.name});
        } else if (seenTypedefsCount == 2) {
          // Cyclicity through one other typedef.
          compiler.reportErrorMessage(
              element,
              MessageKind.CYCLIC_TYPEDEF_ONE,
              {'typedefName': element.name,
               'otherTypedefName': seenTypedefs.head.name});
        } else {
          // Cyclicity through more than one other typedef.
          for (TypedefElement cycle in seenTypedefs) {
            if (!identical(typedefElement, cycle)) {
              compiler.reportErrorMessage(
                  element,
                  MessageKind.CYCLIC_TYPEDEF_ONE,
                  {'typedefName': element.name,
                   'otherTypedefName': cycle.name});
            }
          }
        }
        ErroneousElementX erroneousElement = new ErroneousElementX(
              MessageKind.CYCLIC_TYPEDEF,
              {'typedefName': element.name},
              element.name, element);
        element.alias =
            new MalformedType(erroneousElement, typedefElement.alias);
        element.hasBeenCheckedForCycles = true;
      }
    } else {
      seenTypedefs = seenTypedefs.prepend(typedefElement);
      seenTypedefsCount++;
      type.visitChildren(this, null);
      typedefElement.alias.accept(this, null);
      seenTypedefs = seenTypedefs.tail;
      seenTypedefsCount--;
    }
  }

  visitFunctionType(FunctionType type, _) {
    type.visitChildren(this, null);
  }

  visitInterfaceType(InterfaceType type, _) {
    type.visitChildren(this, null);
  }

  visitTypeVariableType(TypeVariableType type, _) {
    TypeVariableElement typeVariableElement = type.element;
    if (seenTypeVariables.contains(typeVariableElement)) {
      // Avoid running in cycles on cyclic type variable bounds.
      // Cyclicity is reported elsewhere.
      return;
    }
    seenTypeVariables = seenTypeVariables.prepend(typeVariableElement);
    typeVariableElement.bound.accept(this, null);
    seenTypeVariables = seenTypeVariables.tail;
  }
}