Support for using generic function types in other AST structures.

[email protected]
BUG=

Review-Url: https://codereview.chromium.org/2814063003 .

Author: scheglov

pkg/analyzer/lib/src/generated/declaration_resolver.dart

@@ -8,6 +8,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/exception/exception.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/element/builder.dart';
@@ -225,6 +226,7 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
             elementName: functionName.name + '=');
       }
     }
+    _setGenericFunctionType(node.returnType, element.returnType);
     node.functionExpression.element = element;
     _walker._elementHolder?.addFunction(element);
     _walk(new ElementWalker.forExecutable(element, _enclosingUnit), () {
@@ -278,6 +280,7 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
   @override
   Object visitGenericFunctionType(GenericFunctionType node) {
     GenericFunctionTypeElement element = node.type.element;
+    _setGenericFunctionType(node.returnType, element.returnType);
     _walk(new ElementWalker.forGenericFunctionType(element), () {
       super.visitGenericFunctionType(node);
     });
@@ -288,8 +291,7 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
   Object visitGenericTypeAlias(GenericTypeAlias node) {
     GenericTypeAliasElementImpl element =
         _match(node.name, _walker.getTypedef());
-    (node.functionType as GenericFunctionTypeImpl)?.type =
-        element.function?.type;
+    _setGenericFunctionType(node.functionType, element.function?.type);
     _walk(new ElementWalker.forGenericTypeAlias(element), () {
       super.visitGenericTypeAlias(node);
     });
@@ -357,6 +359,7 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
             elementName: nameOfMethod + '=');
       }
     }
+    _setGenericFunctionType(node.returnType, element.returnType);
     _walk(new ElementWalker.forExecutable(element, _enclosingUnit), () {
       super.visitMethodDeclaration(node);
     });
@@ -393,10 +396,7 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
       ParameterElement element =
           _match(node.identifier, _walker.getParameter());
       (node as SimpleFormalParameterImpl).element = element;
-      TypeAnnotation type = node.type;
-      if (type is GenericFunctionTypeImpl) {
-        type.type = element.type;
-      }
+      _setGenericFunctionType(node.type, element.type);
       _walk(new ElementWalker.forParameter(element), () {
         super.visitSimpleFormalParameter(node);
       });
@@ -463,10 +463,13 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
     if (_walker.elementBuilder != null) {
       return _walker.elementBuilder.visitVariableDeclarationList(node);
     } else {
-      super.visitVariableDeclarationList(node);
+      node.variables.accept(this);
+      VariableElement firstVariable = node.variables[0].element;
+      _setGenericFunctionType(node.type, firstVariable.type);
+      node.type?.accept(this);
       if (node.parent is! FieldDeclaration &&
           node.parent is! TopLevelVariableDeclaration) {
-        _resolveMetadata(node, node.metadata, node.variables[0].element);
+        _resolveMetadata(node, node.metadata, firstVariable);
       }
       return null;
     }
@@ -537,6 +540,15 @@ class DeclarationResolver extends RecursiveAstVisitor<Object> {
     }
   }
 
+  /**
+   * If the given [typeNode] is a [GenericFunctionType], set its [type].
+   */
+  void _setGenericFunctionType(TypeAnnotation typeNode, DartType type) {
+    if (typeNode is GenericFunctionTypeImpl) {
+      typeNode.type = type;
+    }
+  }
+
   /**
    * Recurses through the element model and AST, verifying that all elements are
    * matched.

pkg/analyzer/test/generated/declaration_resolver_test.dart

@@ -468,6 +468,58 @@ void set zzz(_) {}
     expect(getterName.staticElement, same(setterElement));
   }
 
+  test_genericFunction_asFunctionReturnType() async {
+    String code = r'''
+Function(int, String) f() => null;
+''';
+    CompilationUnit unit = await resolveSource(code);
+    // re-resolve
+    _cloneResolveUnit(unit);
+    // no other validations than built into DeclarationResolver
+  }
+
+  test_genericFunction_asGenericFunctionReturnType() async {
+    String code = r'''
+typedef F<T> = int Function(T t, S s) Function<S>(int);
+''';
+    CompilationUnit unit = await resolveSource(code);
+    // re-resolve
+    _cloneResolveUnit(unit);
+    // no other validations than built into DeclarationResolver
+  }
+
+  test_genericFunction_asMethodReturnType() async {
+    String code = r'''
+class C {
+  Function(int, String) m() => null;
+}
+''';
+    CompilationUnit unit = await resolveSource(code);
+    // re-resolve
+    _cloneResolveUnit(unit);
+    // no other validations than built into DeclarationResolver
+  }
+
+  test_genericFunction_asParameterReturnType() async {
+    String code = r'''
+f(Function(int, String) p) => null;
+''';
+    CompilationUnit unit = await resolveSource(code);
+    // re-resolve
+    _cloneResolveUnit(unit);
+    // no other validations than built into DeclarationResolver
+  }
+
+  test_genericFunction_asTopLevelVariableType() async {
+    String code = r'''
+int Function(int, String) v;
+''';
+    CompilationUnit unit = await resolveSource(code);
+    // re-resolve
+    _cloneResolveUnit(unit);
+    // no other validations than built into DeclarationResolver
+  }
+
   test_invalid_functionDeclaration_getter_inFunction() async {
     String code = r'''
 var v = (() {