Elements. Implement returning ConstantInitializer.

Change-Id: Ib0f3d569b28396cee2633630d8fc968c4fd822e4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/410900
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>

Author: scheglov

pkg/analyzer/api.txt

@@ -3635,6 +3635,7 @@ package:analyzer/dart/element/element2.dart:
   ConstantInitializer (class extends Object):
     new (constructor: ConstantInitializer Function())
     expression (getter: Expression)
+    fragment (getter: VariableFragment)
     evaluate (method: DartObject? Function())
   ConstructorElement2 (class extends Object implements ExecutableElement2, HasSinceSdkVersion):
     new (constructor: ConstructorElement2 Function())
@@ -4297,7 +4298,7 @@ package:analyzer/dart/element/element2.dart:
     computeConstantValue (method: DartObject? Function())
   VariableFragment (class extends Object implements Fragment):
     new (constructor: VariableFragment Function())
-    constantInitializer2 (getter: ConstantInitializer?)
+    constantInitializer2 (getter: Expression?)
     element (getter: VariableElement2)
     nextFragment (getter: VariableFragment?)
     previousFragment (getter: VariableFragment?)

pkg/analyzer/lib/dart/element/element2.dart

@@ -264,6 +264,11 @@ abstract class ConstantInitializer {
   /// have the default value.
   Expression get expression;
 
+  /// The [VariableFragment] that has [expression].
+  ///
+  /// The offsets are inside the [LibraryFragment] that contains [fragment].
+  VariableFragment get fragment;
+
   /// Returns the result of evaluating [expression], computes it if necessary.
   ///
   /// Returns `null` if the value could not be computed because of errors.
@@ -2890,7 +2895,7 @@ abstract class VariableFragment implements Fragment {
   ///
   /// Is `null` if this variable fragment is not a constant, or does not have
   /// the initializer or the default value specified.
-  ConstantInitializer? get constantInitializer2;
+  Expression? get constantInitializer2;
 
   @override
   VariableElement2 get element;

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

@@ -1337,6 +1337,31 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
   }
 }
 
+class ConstantInitializerImpl implements ConstantInitializer {
+  @override
+  final VariableElementImpl fragment;
+
+  @override
+  final ExpressionImpl expression;
+
+  /// The cached result of [evaluate].
+  Constant? _evaluationResult;
+
+  ConstantInitializerImpl({
+    required this.fragment,
+    required this.expression,
+  });
+
+  @override
+  DartObject? evaluate() {
+    if (_evaluationResult case DartObjectImpl result) {
+      return result;
+    }
+    // TODO(scheglov): implement it
+    throw UnimplementedError();
+  }
+}
+
 /// A [FieldElement] for a 'const' or 'final' field that has an initializer.
 ///
 // TODO(paulberry): we should rename this class to reflect the fact that it's
@@ -4285,6 +4310,11 @@ class ExtensionTypeElementImpl2 extends InterfaceElementImpl2
   }
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `FieldElement2`.
+abstract class FieldElement2OrMember
+    implements PropertyInducingElement2OrMember, FieldElement2 {}
+
 /// A concrete implementation of a [FieldElement].
 class FieldElementImpl extends PropertyInducingElementImpl
     with AugmentableElement<FieldElementImpl>
@@ -4403,7 +4433,7 @@ class FieldElementImpl2 extends PropertyInducingElementImpl2
         FragmentedAnnotatableElementMixin<FieldElementImpl>,
         FragmentedElementMixin<FieldElementImpl>,
         _HasSinceSdkVersionMixin
-    implements FieldElement2 {
+    implements FieldElement2OrMember {
   @override
   final FieldElementImpl firstFragment;
 
@@ -4493,7 +4523,8 @@ class FieldElementImpl2 extends PropertyInducingElementImpl2
 
 /// Common base class for all analyzer-internal classes that implement
 /// `FieldElement`.
-abstract class FieldElementOrMember implements FieldElement {
+abstract class FieldElementOrMember
+    implements PropertyInducingElementOrMember, FieldElement {
   @override
   TypeImpl get type;
 }
@@ -11791,12 +11822,11 @@ abstract class VariableElementImpl extends ElementImpl
   /// initializers.  However, analyzer also needs to handle incorrect Dart code,
   /// in which case there might be some constant variables that lack
   /// initializers.
-  Expression? get constantInitializer => null;
+  ExpressionImpl? get constantInitializer => null;
 
   @override
-  ConstantInitializer? get constantInitializer2 {
-    // TODO(scheglov): implement it
-    throw UnimplementedError();
+  ExpressionImpl? get constantInitializer2 {
+    return constantInitializer;
   }
 
   @override
@@ -11896,10 +11926,24 @@ abstract class VariableElementImpl extends ElementImpl
 
 abstract class VariableElementImpl2 extends ElementImpl2
     implements VariableElement2OrMember {
+  ConstantInitializerImpl? _constantInitializer;
+
   @override
   ConstantInitializer? get constantInitializer2 {
-    // TODO(scheglov): implement it
-    throw UnimplementedError();
+    if (_constantInitializer case var result?) {
+      return result;
+    }
+
+    for (var fragment in fragments.reversed) {
+      if (fragment.constantInitializer2 case ExpressionImpl expression) {
+        return _constantInitializer = ConstantInitializerImpl(
+          fragment: fragment as VariableElementImpl,
+          expression: expression,
+        );
+      }
+    }
+
+    return null;
   }
 
   @override

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

@@ -530,12 +530,7 @@ class FieldFormalParameterMember extends ParameterMember
 /// A field element defined in a parameterized type where the values of the type
 /// parameters are known.
 class FieldMember extends VariableMember
-    implements
-        FieldElementOrMember,
-        FieldElement2,
-        VariableElement2OrMember,
-        PropertyInducingElementOrMember,
-        PropertyInducingElement2OrMember {
+    implements FieldElementOrMember, FieldElement2OrMember {
   /// Initialize a newly created element to represent a field, based on the
   /// [declaration], with applied [substitution].
   FieldMember(
@@ -563,8 +558,7 @@ class FieldMember extends VariableMember
 
   @override
   ConstantInitializer? get constantInitializer2 {
-    // TODO(scheglov): implement it
-    throw UnimplementedError();
+    return baseElement.constantInitializer2;
   }
 
   @override
@@ -1229,8 +1223,7 @@ class ParameterMember extends VariableMember
 
   @override
   ConstantInitializer? get constantInitializer2 {
-    // TODO(scheglov): implement it
-    throw UnimplementedError();
+    return baseElement.constantInitializer2;
   }
 
   @override

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

@@ -2510,7 +2510,7 @@ class ResolverVisitor extends ThrowingAstVisitor<void>
 
     var element = node.declaredElement!;
     var initializer = element.constantInitializer;
-    if (initializer is InstanceCreationExpression) {
+    if (initializer is InstanceCreationExpressionImpl) {
       var constructorName = initializer.constructorName;
       var constructorElement = constructorName.staticElement;
       if (constructorElement != null) {

pkg/analyzer/test/src/summary/element_text.dart

@@ -288,6 +288,18 @@ class _Element2Writer extends _AbstractElementWriter {
     expect(element.nonSynthetic2, same(element));
   }
 
+  void _writeConstantInitializerExpression(String name, Expression expression) {
+    if (_idMap.existingExpressionId(expression) case var id?) {
+      _sink.writelnWithIndent('$name: $id');
+    } else {
+      var id = _idMap[expression];
+      _sink.writelnWithIndent('$name: $id');
+      _sink.withIndent(() {
+        _writeNode(expression);
+      });
+    }
+  }
+
   void _writeConstructorElement(ConstructorElement2 e) {
     // Check that the reference exists, and filled with the element.
     // var reference = e.reference;
@@ -510,6 +522,7 @@ class _Element2Writer extends _AbstractElementWriter {
   }
 
   void _writeFieldElement(FieldElement2 e) {
+    e as FieldElement2OrMember;
     DartType type = e.type;
     expect(type, isNotNull);
 
@@ -565,7 +578,7 @@ class _Element2Writer extends _AbstractElementWriter {
       // _writeTypeInferenceError(e);
       _writeType('type', e.type);
       // _writeShouldUseTypeForInitializerInference(e);
-      // _writeConstantInitializer(e);
+      _writeVariableElementConstantInitializer(e);
       // _writeNonSyntheticElement(e);
       // writeLinking();
       _writeElementReference('getter', e.getter2);
@@ -623,7 +636,7 @@ class _Element2Writer extends _AbstractElementWriter {
       // _writeTypeInferenceError(f);
       // _writeType('type', f.type);
       // _writeShouldUseTypeForInitializerInference(f);
-      // _writeConstantInitializer(f);
+      _writeVariableFragmentConstantInitializer(f);
       // _writeNonSyntheticElement(f);
       // writeLinking();
       _writeFragmentReference('previousFragment', f.previousFragment);
@@ -634,6 +647,7 @@ class _Element2Writer extends _AbstractElementWriter {
   }
 
   void _writeFormalParameterElement(FormalParameterElement e) {
+    e as FormalParameterElementMixin;
     // if (e.isNamed && e.enclosingElement2 is ExecutableElement) {
     //   expect(e.reference, isNotNull);
     // } else {
@@ -688,7 +702,7 @@ class _Element2Writer extends _AbstractElementWriter {
         e.formalParameters,
         _writeFormalParameterElement,
       );
-      // _writeConstantInitializer(e);
+      _writeVariableElementConstantInitializer(e);
       // _writeNonSyntheticElement(e);
       // _writeFieldFormalParameterField(e);
       // _writeSuperConstructorParameter(e);
@@ -739,7 +753,7 @@ class _Element2Writer extends _AbstractElementWriter {
       // _writeCodeRange(f);
       // _writeTypeParameterElements(e.typeParameters);
       // _writeFragmentList('parameters', f, f.parameters2, _writeFormalParameterFragments);
-      // _writeConstantInitializer(e);
+      _writeVariableFragmentConstantInitializer(f);
       // _writeNonSyntheticElement(e);
       // _writeFieldFormalParameterField(e);
       // _writeSuperConstructorParameter(e);
@@ -1626,7 +1640,7 @@ class _Element2Writer extends _AbstractElementWriter {
       // _writeTypeInferenceError(e);
       _writeType('type', e.type);
       // _writeShouldUseTypeForInitializerInference(e);
-      // _writeConstantInitializer(e);
+      _writeVariableElementConstantInitializer(e);
       // _writeNonSyntheticElement(e);
       // writeLinking();
       _writeElementReference('getter', e.getter2);
@@ -1682,7 +1696,7 @@ class _Element2Writer extends _AbstractElementWriter {
       // _writeTypeInferenceError(f);
       // _writeType('type', f.type);
       // _writeShouldUseTypeForInitializerInference(f);
-      // _writeConstantInitializer(f);
+      _writeVariableFragmentConstantInitializer(f);
       // _writeNonSyntheticElement(f);
       // writeLinking();
       _writeFragmentReference('previousFragment', f.previousFragment);
@@ -1828,6 +1842,25 @@ class _Element2Writer extends _AbstractElementWriter {
 
     // _assertNonSyntheticElementSelf(f);
   }
+
+  void _writeVariableElementConstantInitializer(VariableElement2OrMember e) {
+    if (e.constantInitializer2 case var initializer?) {
+      _sink.writelnWithIndent('constantInitializer');
+      _sink.withIndent(() {
+        _writeFragmentReference('fragment', initializer.fragment);
+        _writeConstantInitializerExpression(
+          'expression',
+          initializer.expression,
+        );
+      });
+    }
+  }
+
+  void _writeVariableFragmentConstantInitializer(VariableFragment f) {
+    if (f.constantInitializer2 case var initializer?) {
+      _writeConstantInitializerExpression('constantInitializer', initializer);
+    }
+  }
 }
 
 /// Writes the canonical text presentation of elements.
@@ -2943,24 +2976,31 @@ class _ElementWriter extends _AbstractElementWriter {
 }
 
 class _IdMap {
+  final Map<Expression, String> expressionMap = Map.identity();
   final Map<Element, String> fieldMap = Map.identity();
   final Map<Element, String> getterMap = Map.identity();
   final Map<Element, String> partMap = Map.identity();
   final Map<Element, String> setterMap = Map.identity();
 
-  String operator [](Element element) {
-    if (element is FieldElement) {
-      return fieldMap[element] ??= 'field_${fieldMap.length}';
-    } else if (element is TopLevelVariableElement) {
-      return fieldMap[element] ??= 'variable_${fieldMap.length}';
-    } else if (element is PropertyAccessorElement && element.isGetter) {
-      return getterMap[element] ??= 'getter_${getterMap.length}';
-    } else if (element is PartElementImpl) {
-      return partMap[element] ??= 'part_${partMap.length}';
-    } else if (element is PropertyAccessorElement && element.isSetter) {
-      return setterMap[element] ??= 'setter_${setterMap.length}';
+  String operator [](Object object) {
+    if (object is Expression) {
+      return expressionMap[object] ??= 'expression_${expressionMap.length}';
+    } else if (object is FieldElement) {
+      return fieldMap[object] ??= 'field_${fieldMap.length}';
+    } else if (object is TopLevelVariableElement) {
+      return fieldMap[object] ??= 'variable_${fieldMap.length}';
+    } else if (object is PropertyAccessorElement && object.isGetter) {
+      return getterMap[object] ??= 'getter_${getterMap.length}';
+    } else if (object is PartElementImpl) {
+      return partMap[object] ??= 'part_${partMap.length}';
+    } else if (object is PropertyAccessorElement && object.isSetter) {
+      return setterMap[object] ??= 'setter_${setterMap.length}';
     } else {
       return '???';
     }
   }
+
+  String? existingExpressionId(Expression object) {
+    return expressionMap[object];
+  }
 }