Add LocalVariableElement/PropertyInducingElement.hasInitializer, ParameterElement.hasDefaultValue, deprecate VariableElement.initializer

Change-Id: I02ba37b4f6f1ce79ffddf40613646b99ecbedc9d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/159582
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.40.1-dev
+* Added `LocalVariableElement.hasInitializer`,
+  `PropertyInducingElement.hasInitializer`, `ParameterElement.hasDefaultValue`.
+
 ## 0.40.0
 * Added `LibraryElement.featureSet`.
 * Removed deprecated `EmbedderSdk` and related classes.

pkg/analyzer/lib/dart/element/element.dart

@@ -1388,7 +1388,10 @@ abstract class LocalElement implements Element {}
 /// A local variable.
 ///
 /// Clients may not extend, implement or mix-in this class.
-abstract class LocalVariableElement implements PromotableElement {}
+abstract class LocalVariableElement implements PromotableElement {
+  /// Return `true` if this variable has an initializer at declaration.
+  bool get hasInitializer;
+}
 
 /// An element that represents a method defined within a class.
 ///
@@ -1440,6 +1443,9 @@ abstract class ParameterElement
   /// Return the Dart code of the default value, or `null` if no default value.
   String get defaultValueCode;
 
+  /// Return `true` if this parameter has a default value.
+  bool get hasDefaultValue;
+
   /// Return `true` if this parameter is covariant, meaning it is allowed to
   /// have a narrower type in an override.
   bool get isCovariant;
@@ -1598,6 +1604,9 @@ abstract class PropertyInducingElement implements VariableElement {
   /// will be synthetic.
   PropertyAccessorElement get getter;
 
+  /// Return `true` if this variable has an initializer at declaration.
+  bool get hasInitializer;
+
   /// Return the setter associated with this variable, or `null` if the variable
   /// is effectively `final` and therefore does not have a setter associated
   /// with it. (This can happen either because the variable is explicitly
@@ -1728,6 +1737,7 @@ abstract class VariableElement implements Element, ConstantEvaluationTarget {
   /// `null` if this variable does not have an initializer. The function will
   /// have no parameters. The return type of the function will be the
   /// compile-time type of the initialization expression.
+  @deprecated
   FunctionElement get initializer;
 
   /// Return `true` if this variable was declared with the 'const' modifier.

pkg/analyzer/lib/src/dart/constant/evaluation.dart

@@ -369,7 +369,7 @@ class ConstantEvaluationEngine {
           // that we won't be confused by incorrect code.
           if ((field.isFinal || field.isConst) &&
               !field.isStatic &&
-              field.initializer != null) {
+              field.hasInitializer) {
             callback(field);
           }
         }

pkg/analyzer/lib/src/dart/element/element.dart

@@ -1783,6 +1783,9 @@ class ConstFieldElementImpl_EnumValue extends ConstFieldElementImpl_ofEnum {
     return _evaluationResult;
   }
 
+  @override
+  bool get hasInitializer => false;
+
   @override
   String get name {
     if (linkedNode != null) {
@@ -5615,6 +5618,9 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
 /// A concrete implementation of a [LocalVariableElement].
 class LocalVariableElementImpl extends NonParameterVariableElementImpl
     implements LocalVariableElement {
+  @override
+  bool hasInitializer;
+
   /// Initialize a newly created method element to have the given [name] and
   /// [offset].
   LocalVariableElementImpl(String name, int offset) : super(name, offset);
@@ -6218,24 +6224,26 @@ abstract class NonParameterVariableElementImpl extends VariableElementImpl {
     super.hasImplicitType = hasImplicitType;
   }
 
+  bool get hasInitializer {
+    return linkedNode != null && linkedContext.hasInitializer(linkedNode);
+  }
+
+  @deprecated
   @override
   FunctionElement get initializer {
-    if (_initializer == null) {
-      if (linkedNode != null) {
-        if (linkedContext.hasInitializer(linkedNode)) {
-          _initializer = FunctionElementImpl('', -1)
-            ..isSynthetic = true
-            .._type = FunctionTypeImpl(
-              typeFormals: const [],
-              parameters: const [],
-              returnType: type,
-              nullabilitySuffix: NullabilitySuffix.star,
-            )
-            ..enclosingElement = this;
-        }
-      }
+    if (hasInitializer) {
+      return FunctionElementImpl('', -1)
+        ..enclosingElement = this
+        ..isSynthetic = true
+        ..returnType = type
+        .._type = FunctionTypeImpl(
+          typeFormals: const [],
+          parameters: const [],
+          returnType: type,
+          nullabilitySuffix: NullabilitySuffix.star,
+        );
     }
-    return super.initializer;
+    return null;
   }
 
   @override
@@ -6278,19 +6286,16 @@ abstract class NonParameterVariableElementImpl extends VariableElementImpl {
     return null;
   }
 
-  bool get _hasInitializer {
-    return linkedNode != null && linkedContext.hasInitializer(linkedNode);
-  }
-
   /// Return `true` if this variable needs the setter.
   bool get _hasSetter {
     if (isConst) {
       return false;
     }
 
+    // TODO(scheglov) is this right?
     if (isLate) {
       if (isFinal) {
-        return !_hasInitializer;
+        return !hasInitializer;
       }
       return true;
     }
@@ -6388,6 +6393,11 @@ class ParameterElementImpl extends VariableElementImpl
     _defaultValueCode = StringUtilities.intern(defaultValueCode);
   }
 
+  @override
+  bool get hasDefaultValue {
+    return defaultValueCode != null;
+  }
+
   @override
   bool get hasImplicitType {
     if (linkedNode != null) {
@@ -6420,28 +6430,6 @@ class ParameterElementImpl extends VariableElementImpl
     _inheritsCovariant = value;
   }
 
-  @override
-  FunctionElement get initializer {
-    if (_initializer != null) return _initializer;
-
-    if (linkedNode != null) {
-      if (linkedContext.hasDefaultValue(linkedNode)) {
-        _initializer = FunctionElementImpl('', -1)
-          ..enclosingElement = this
-          ..isSynthetic = true;
-      }
-    }
-
-    return super.initializer;
-  }
-
-  /// Set the function representing this variable's initializer to the given
-  /// [function].
-  @override
-  set initializer(FunctionElement function) {
-    super.initializer = function;
-  }
-
   @override
   bool get isCovariant {
     if (isExplicitlyCovariant || inheritsCovariant) {
@@ -7112,6 +7100,10 @@ abstract class PropertyInducingElementImpl
   @override
   PropertyAccessorElement setter;
 
+  /// This field is set during linking, and performs type inference for
+  /// this property. After linking this field is always `null`.
+  PropertyInducingElementTypeInference typeInference;
+
   /// Initialize a newly created synthetic element to have the given [name] and
   /// [offset].
   PropertyInducingElementImpl(String name, int offset) : super(name, offset);
@@ -7156,6 +7148,12 @@ abstract class PropertyInducingElementImpl
   }
 }
 
+/// Instances of this class are set for fields and top-level variables
+/// to perform top-level type inference during linking.
+abstract class PropertyInducingElementTypeInference {
+  void perform();
+}
+
 /// A concrete implementation of a [ShowElementCombinator].
 class ShowElementCombinatorImpl implements ShowElementCombinator {
   final LinkedUnitContext linkedContext;
@@ -7557,10 +7555,6 @@ abstract class VariableElementImpl extends ElementImpl
   /// The type of this variable.
   DartType _type;
 
-  /// A synthetic function representing this variable's initializer, or `null
-  ///` if this variable does not have an initializer.
-  FunctionElement _initializer;
-
   /// Initialize a newly created variable element to have the given [name] and
   /// [offset].
   VariableElementImpl(String name, int offset) : super(name, offset);
@@ -7613,17 +7607,9 @@ abstract class VariableElementImpl extends ElementImpl
     setModifier(Modifier.IMPLICIT_TYPE, hasImplicitType);
   }
 
+  @deprecated
   @override
-  FunctionElement get initializer => _initializer;
-
-  /// Set the function representing this variable's initializer to the given
-  /// [function].
-  set initializer(FunctionElement function) {
-    if (function != null) {
-      (function as FunctionElementImpl).enclosingElement = this;
-    }
-    _initializer = function;
-  }
+  FunctionElement get initializer => null;
 
   @override
   bool get isConst {
@@ -7684,6 +7670,7 @@ abstract class VariableElementImpl extends ElementImpl
   @override
   void visitChildren(ElementVisitor visitor) {
     super.visitChildren(visitor);
-    _initializer?.accept(visitor);
+    // ignore: deprecated_member_use_from_same_package
+    initializer?.accept(visitor);
   }
 }

pkg/analyzer/lib/src/dart/element/member.dart

@@ -211,8 +211,6 @@ abstract class ExecutableMember extends Member implements ExecutableElement {
 
   @override
   void visitChildren(ElementVisitor visitor) {
-    // TODO(brianwilkerson) We need to finish implementing the accessors used
-    // below so that we can safely invoke them.
     super.visitChildren(visitor);
     safelyVisitChildren(parameters, visitor);
   }
@@ -295,6 +293,9 @@ class FieldFormalParameterMember extends ParameterMember
     return FieldMember(field, _substitution, isLegacy);
   }
 
+  @override
+  bool get hasDefaultValue => declaration.hasDefaultValue;
+
   @override
   bool get isCovariant => declaration.isCovariant;
 
@@ -333,6 +334,9 @@ class FieldMember extends VariableMember implements FieldElement {
     return PropertyAccessorMember(baseGetter, _substitution, isLegacy);
   }
 
+  @override
+  bool get hasInitializer => declaration.hasInitializer;
+
   @override
   bool get isAbstract => declaration.isAbstract;
 
@@ -771,6 +775,9 @@ class ParameterMember extends VariableMember
   @override
   Element get enclosingElement => declaration.enclosingElement;
 
+  @override
+  bool get hasDefaultValue => declaration.hasDefaultValue;
+
   @override
   int get hashCode => declaration.hashCode;
 
@@ -950,6 +957,9 @@ class TopLevelVariableMember extends VariableMember
     return PropertyAccessorMember(baseGetter, _substitution, isLegacy);
   }
 
+  @override
+  bool get hasInitializer => declaration.hasInitializer;
+
   @override
   bool get isExternal => declaration.isExternal;
 
@@ -1039,9 +1049,8 @@ abstract class VariableMember extends Member implements VariableElement {
 
   @override
   void visitChildren(ElementVisitor visitor) {
-    // TODO(brianwilkerson) We need to finish implementing the accessors used
-    // below so that we can safely invoke them.
     super.visitChildren(visitor);
+    // ignore: deprecated_member_use_from_same_package
     declaration.initializer?.accept(visitor);
   }
 }

pkg/analyzer/lib/src/dart/resolver/flow_analysis_visitor.dart

@@ -344,7 +344,7 @@ class TypeSystemTypeOperations
   bool isLocalVariableWithoutDeclaredType(PromotableElement variable) {
     return variable is LocalVariableElement &&
         variable.hasImplicitType &&
-        variable.initializer == null;
+        !variable.hasInitializer;
   }
 
   @override

pkg/analyzer/lib/src/dart/resolver/resolution_visitor.dart

@@ -369,14 +369,7 @@ class ResolutionVisitor extends RecursiveAstVisitor<void> {
     var defaultValue = node.defaultValue;
     if (defaultValue != null) {
       _withElementWalker(null, () {
-        var offset = defaultValue.offset;
-        var initializer = FunctionElementImpl.forOffset(offset);
-        element.initializer = initializer;
-
-        initializer.hasImplicitReturnType = true;
-        initializer.isSynthetic = true;
-
-        _withElementHolder(ElementHolder(initializer), () {
+        _withElementHolder(ElementHolder(element), () {
           defaultValue.accept(this);
         });
       });
@@ -962,19 +955,13 @@ class ResolutionVisitor extends RecursiveAstVisitor<void> {
 
       VariableDeclarationList varList = node.parent;
       localElement.hasImplicitType = varList.type == null;
+      localElement.hasInitializer = initializerNode != null;
       localElement.type = varList.type?.type ?? _dynamicType;
     }
 
     if (initializerNode != null) {
       _withElementWalker(null, () {
-        var offset = initializerNode.offset;
-        var initializer = FunctionElementImpl.forOffset(offset);
-        element.initializer = initializer;
-
-        initializer.hasImplicitReturnType = true;
-        initializer.isSynthetic = true;
-
-        _withElementHolder(ElementHolder(initializer), () {
+        _withElementHolder(ElementHolder(element), () {
           initializerNode.accept(this);
         });
       });

pkg/analyzer/lib/src/dart/resolver/variable_declaration_resolver.dart

@@ -61,11 +61,6 @@ class VariableDeclarationResolver {
       _setInferredType(element, initializer.staticType);
     }
 
-    if (element.initializer != null) {
-      var initializerFunction = element.initializer as FunctionElementImpl;
-      initializerFunction.returnType = initializer.staticType;
-    }
-
     if (isTopLevel) {
       _flowAnalysis?.topLevelDeclaration_exit();
     }

pkg/analyzer/lib/src/error/constructor_fields_verifier.dart

@@ -98,9 +98,9 @@ class ConstructorFieldsVerifier {
     _initialFieldMap = <FieldElement, _InitState>{};
     for (var field in element.fields) {
       if (!field.isSynthetic) {
-        _initialFieldMap[field] = field.initializer == null
-            ? _InitState.notInit
-            : _InitState.initInDeclaration;
+        _initialFieldMap[field] = field.hasInitializer
+            ? _InitState.initInDeclaration
+            : _InitState.notInit;
       }
     }
   }

pkg/analyzer/lib/src/error/inheritance_override.dart

@@ -422,13 +422,13 @@ class _ClassVerifier {
         var derivedElement = derivedOptionalElements[i];
         if (_isNonNullableByDefault &&
             derivedIsAbstract &&
-            derivedElement.initializer == null) {
+            !derivedElement.hasDefaultValue) {
           continue;
         }
         var name = derivedElement.name;
         for (var j = 0; j < baseOptionalElements.length; j++) {
           var baseParameter = baseOptionalElements[j];
-          if (name == baseParameter.name && baseParameter.initializer != null) {
+          if (name == baseParameter.name && baseParameter.hasDefaultValue) {
             var baseValue = baseParameter.computeConstantValue();
             var derivedResult = derivedElement.evaluationResult;
             if (!_constantValuesEqual(derivedResult.value, baseValue)) {
@@ -453,11 +453,11 @@ class _ClassVerifier {
         var derivedElement = derivedOptionalElements[i];
         if (_isNonNullableByDefault &&
             derivedIsAbstract &&
-            derivedElement.initializer == null) {
+            !derivedElement.hasDefaultValue) {
           continue;
         }
         var baseElement = baseOptionalElements[i];
-        if (baseElement.initializer != null) {
+        if (baseElement.hasDefaultValue) {
           var baseValue = baseElement.computeConstantValue();
           var derivedResult = derivedElement.evaluationResult;
           if (!_constantValuesEqual(derivedResult.value, baseValue)) {

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

@@ -1003,10 +1003,6 @@ class ResolverVisitor extends ScopedVisitor {
     super.visitDefaultFormalParameter(node);
     ParameterElement element = node.declaredElement;
 
-    if (element.initializer != null && node.defaultValue != null) {
-      (element.initializer as FunctionElementImpl).returnType =
-          node.defaultValue.staticType;
-    }
     // Clone the ASTs for default formal parameters, so that we can use them
     // during constant evaluation.
     if (element is ConstVariableElement &&

pkg/analyzer/lib/src/summary2/top_level_inference.dart

@@ -11,7 +11,6 @@ import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/type_demotion.dart';
 import 'package:analyzer/src/dart/element/type_system.dart';
-import 'package:analyzer/src/generated/element_type_provider.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/idl.dart';
@@ -197,31 +196,6 @@ class _ConstructorInferenceNode extends _InferenceNode {
   }
 }
 
-class _FunctionElementForLink_Initializer
-    implements FunctionElementImpl, ElementImplWithFunctionType {
-  final _VariableInferenceNode _node;
-
-  @override
-  Element enclosingElement;
-
-  _FunctionElementForLink_Initializer(this._node);
-
-  @override
-  DartType get returnType =>
-      ElementTypeProvider.current.getExecutableReturnType(this);
-
-  @override
-  DartType get returnTypeInternal {
-    if (!_node.isEvaluated) {
-      _node._walker.walk(_node);
-    }
-    return LazyAst.getType(_node._node);
-  }
-
-  @override
-  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
-}
-
 class _InferenceDependenciesCollector extends RecursiveAstVisitor<void> {
   final Set<Element> _set = Set.identity();
 
@@ -356,14 +330,28 @@ class _InitializerInference {
       var inferenceNode =
           _VariableInferenceNode(_walker, _unitElement, _scope, node);
       _walker._nodes[element] = inferenceNode;
-      (element as PropertyInducingElementImpl).initializer =
-          _FunctionElementForLink_Initializer(inferenceNode);
+      (element as PropertyInducingElementImpl).typeInference =
+          _PropertyInducingElementTypeInference(inferenceNode);
     } else {
       LazyAst.setType(node, DynamicTypeImpl.instance);
     }
   }
 }
 
+class _PropertyInducingElementTypeInference
+    implements PropertyInducingElementTypeInference {
+  final _VariableInferenceNode _node;
+
+  _PropertyInducingElementTypeInference(this._node);
+
+  @override
+  void perform() {
+    if (!_node.isEvaluated) {
+      _node._walker.walk(_node);
+    }
+  }
+}
+
 class _VariableInferenceNode extends _InferenceNode {
   final _InferenceWalker _walker;
   final CompilationUnitElement _unitElement;

pkg/analyzer/lib/src/task/strong_mode.dart

@@ -292,15 +292,7 @@ class InstanceMemberInferrer {
 
       // Otherwise, declarations of static variables and fields that omit a
       // type will be inferred from their initializer if present.
-      var initializer = field.initializer;
-      if (initializer != null) {
-        var initializerType = initializer.returnType;
-        if (initializerType == null || initializerType.isDartCoreNull) {
-          initializerType = _dynamicType;
-        }
-        field.type = initializerType;
-        return;
-      }
+      field.typeInference?.perform();
 
       return;
     }

pkg/analyzer/pubspec.yaml

@@ -1,5 +1,5 @@
 name: analyzer
-version: 0.40.0
+version: 0.40.1-dev
 description: This package provides a library that performs static analysis of Dart code.
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/analyzer
 

pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart

@@ -1056,12 +1056,11 @@ class C {
     ClassDeclaration c = unit.declarations[0];
     FieldDeclaration declaration = c.members[0];
     VariableDeclaration field = declaration.fields.variables[0];
-    FunctionElement fieldInitializer = field.declaredElement.initializer;
 
     FunctionExpressionInvocation invocation = field.initializer;
     FunctionExpression closure = invocation.function.unParenthesized;
     FunctionElementImpl closureElement = closure.declaredElement;
-    expect(closureElement.enclosingElement, same(fieldInitializer));
+    expect(closureElement, isNotNull);
   }
 
   test_closure_inTopLevelVariable() async {
@@ -1073,13 +1072,11 @@ var v = (() => 42)();
 
     TopLevelVariableDeclaration declaration = unit.declarations[0];
     VariableDeclaration variable = declaration.variables.variables[0];
-    TopLevelVariableElement variableElement = variable.declaredElement;
-    FunctionElement variableInitializer = variableElement.initializer;
 
     FunctionExpressionInvocation invocation = variable.initializer;
     FunctionExpression closure = invocation.function.unParenthesized;
     FunctionElementImpl closureElement = closure.declaredElement;
-    expect(closureElement.enclosingElement, same(variableInitializer));
+    expect(closureElement, isNotNull);
   }
 
   test_conditionalExpression() async {

pkg/analyzer/test/src/task/strong/inferred_type_test.dart

@@ -354,26 +354,19 @@ main() {
   }
 
   test_bottom() async {
-    // When a type is inferred from the expression `null`, the inferred type is
-    // `dynamic`, but the inferred type of the initializer is `bottom`.
-    // TODO(paulberry): Is this intentional/desirable?
     await assertNoErrorsInCode('''
 var v = null;
 ''');
     var v = _resultUnitElement.topLevelVariables[0];
     _assertTypeStr(v.type, 'dynamic');
-    _assertTypeStr(v.initializer.type, 'Null Function()');
   }
 
   test_bottom_inClosure() async {
-    // When a closure's return type is inferred from the expression `null`, the
-    // inferred type is `dynamic`.
     await assertNoErrorsInCode('''
 var v = () => null;
 ''');
     var v = _resultUnitElement.topLevelVariables[0];
     _assertTypeStr(v.type, 'Null Function()');
-    _assertTypeStr(v.initializer.type, 'Null Function() Function()');
   }
 
   test_circularReference_viaClosures() async {
@@ -406,8 +399,8 @@ var y = () => x;
     var y = _resultUnitElement.topLevelVariables[1];
     expect(x.name, 'x');
     expect(y.name, 'y');
-    _assertTypeStr(x.initializer.returnType, 'dynamic Function()');
-    _assertTypeStr(y.initializer.returnType, 'dynamic Function()');
+    _assertTypeStr(x.type, 'dynamic');
+    _assertTypeStr(y.type, 'dynamic');
   }
 
   test_conflictsCanHappen2() async {
@@ -4117,7 +4110,7 @@ main() {
     ]);
 
     var y = findLocalVariable(_resultUnit, 'y');
-    _assertTypeStr(y.initializer.returnType, 'List<num>');
+    _assertTypeStr(y.type, 'List<num>');
   }
 
   test_nullLiteralShouldNotInferAsBottom() async {