Elements. Deprecate supertype, mixins, and interfaces on InterfaceFragment

Deprecate the `supertype`, `mixins`, and `interfaces` getters on
`InterfaceFragment`. This information more accurately belongs on the
`InterfaceElement`, which represents the fully merged view of a class,
rather than on a single fragment declaration.

This change is part of an ongoing effort to consolidate class hierarchy
information at the element level. All internal call sites have been
updated to use the corresponding getters on `InterfaceElement`.

As part of this refactoring, the `isValidMixin` logic has also been
moved from `ClassFragmentImpl` to `ClassElementImpl` to align with this
principle.

Change-Id: Ia919eaa6328451d186e9f67e2c1bb8605856f109
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/445561
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Paul Berry <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: scheglov

pkg/analysis_server/lib/src/services/completion/dart/in_scope_completion_pass.dart

@@ -2752,8 +2752,8 @@ class InScopeCompletionPass extends SimpleAstVisitor<void> {
         offset <= node.argumentList.offset) {
       var container = constructor.parent;
       var superType = switch (container) {
-        ClassDeclaration() => container.declaredFragment?.supertype,
-        EnumDeclaration() => container.declaredFragment?.supertype,
+        ClassDeclaration() => container.declaredFragment?.element.supertype,
+        EnumDeclaration() => container.declaredFragment?.element.supertype,
         _ => null,
       };
       if (superType != null) {

pkg/analyzer/CHANGELOG.md

@@ -9,6 +9,9 @@
   Use `DeclaredVariablePattern.declaredFragment` instead.
 * Deprecate `VariableDeclaration.declaredElement` and `VariableDeclaration.declaredElement2`.
   Use `VariableDeclaration.declaredFragment` instead.
+* Deprecate `InterfaceFragment.interfaces`, use `InterfaceElement.interfaces` instead.
+* Deprecate `InterfaceFragment.mixins`, use `InterfaceElement.mixins` instead.
+* Deprecate `InterfaceFragment.supertype`, use `InterfaceElement.supertype` instead.
 
 ## 8.1.1
 * Fix for `EnumSet` usage when compiled to JavaScript.

pkg/analyzer/api.txt

@@ -3780,11 +3780,11 @@ package:analyzer/dart/element/element.dart:
     constructors (getter: List<ConstructorFragment>)
     constructors2 (getter: List<ConstructorFragment>, deprecated)
     element (getter: InterfaceElement)
-    interfaces (getter: List<InterfaceType>)
-    mixins (getter: List<InterfaceType>)
+    interfaces (getter: List<InterfaceType>, deprecated)
+    mixins (getter: List<InterfaceType>, deprecated)
     nextFragment (getter: InterfaceFragment?)
     previousFragment (getter: InterfaceFragment?)
-    supertype (getter: InterfaceType?)
+    supertype (getter: InterfaceType?, deprecated)
   JoinPatternVariableElement (class extends Object implements PatternVariableElement):
     new (constructor: JoinPatternVariableElement Function())
     firstFragment (getter: JoinPatternVariableFragment)

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

@@ -2516,13 +2516,15 @@ abstract class InterfaceFragment implements InstanceFragment {
   InterfaceElement get element;
 
   /// The interfaces that are implemented by this fragment.
+  @Deprecated('Use InterfaceElement.interfaces instead')
   List<InterfaceType> get interfaces;
 
   /// The mixins that are applied by this fragment.
   ///
   /// [ClassFragment] and [EnumFragment] can have mixins.
   ///
   /// [MixinFragment] cannot have mixins, so the empty list is returned.
+  @Deprecated('Use InterfaceElement.mixins instead')
   List<InterfaceType> get mixins;
 
   @override
@@ -2532,6 +2534,7 @@ abstract class InterfaceFragment implements InstanceFragment {
   InterfaceFragment? get previousFragment;
 
   /// The superclass declared by this fragment.
+  @Deprecated('Use InterfaceElement.supertype instead')
   InterfaceType? get supertype;
 }
 

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

@@ -417,7 +417,18 @@ class ClassElementImpl extends InterfaceElementImpl implements ClassElement {
 
   @override
   @trackedIncludedInId
-  bool get isValidMixin => firstFragment.isValidMixin;
+  bool get isValidMixin {
+    var supertype = this.supertype;
+    if (supertype != null && !supertype.isDartCoreObject) {
+      return false;
+    }
+    for (var constructor in constructors) {
+      if (!constructor.isSynthetic && !constructor.isFactory) {
+        return false;
+      }
+    }
+    return true;
+  }
 
   @override
   ElementKind get kind => ElementKind.CLASS;
@@ -633,19 +644,6 @@ class ClassFragmentImpl extends InterfaceFragmentImpl
 
   bool get isExhaustive => isSealed;
 
-  bool get isValidMixin {
-    var supertype = this.supertype;
-    if (supertype != null && !supertype.isDartCoreObject) {
-      return false;
-    }
-    for (var constructor in constructors) {
-      if (!constructor.isSynthetic && !constructor.isFactory) {
-        return false;
-      }
-    }
-    return true;
-  }
-
   @override
   ClassFragmentImpl? get nextFragment {
     return super.nextFragment as ClassFragmentImpl?;
@@ -4998,10 +4996,11 @@ abstract class InterfaceFragmentImpl extends InstanceFragmentImpl
   @override
   InterfaceElementImpl get element;
 
+  @Deprecated('Use InterfaceElement.interfaces instead')
   @override
   List<InterfaceTypeImpl> get interfaces => element.interfaces;
 
-
+  @Deprecated('Use InterfaceElement.mixins instead')
   @override
   List<InterfaceTypeImpl> get mixins => element.mixins;
 
@@ -5015,6 +5014,7 @@ abstract class InterfaceFragmentImpl extends InstanceFragmentImpl
     return super.previousFragment as InterfaceFragmentImpl?;
   }
 
+  @Deprecated('Use InterfaceElement.supertype instead')
   @override
   InterfaceTypeImpl? get supertype => element.supertype;
 
@@ -7652,6 +7652,7 @@ class MixinFragmentImpl extends InterfaceFragmentImpl
   /// given [offset] in the file that contains the declaration of this element.
   MixinFragmentImpl({required super.name});
 
+  @Deprecated('Use InterfaceElement.mixins instead')
   @override
   List<InterfaceTypeImpl> get mixins => const [];
 
@@ -7668,6 +7669,7 @@ class MixinFragmentImpl extends InterfaceFragmentImpl
     return element.superclassConstraints;
   }
 
+  @Deprecated('Use InterfaceElement.supertype instead')
   @override
   InterfaceTypeImpl? get supertype => null;
 

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

@@ -4303,8 +4303,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
 
     var mixinSupertype = mixinElement.supertype;
     if (mixinSupertype == null || mixinSupertype.isDartCoreObject) {
-      // TODO(scheglov): don't use firstFragment
-      var mixins = mixinElement.firstFragment.mixins;
+      var mixins = mixinElement.mixins;
       if (mixins.isEmpty ||
           mixinElement.isMixinApplication && mixins.length < 2) {
         return false;
@@ -4588,7 +4587,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
       return;
     }
     // prepare super
-    var superType = fragment.supertype;
+    var superType = fragment.element.supertype;
     if (superType == null) {
       return;
     }

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

@@ -380,7 +380,7 @@ class LibraryBuilder {
         case ClassFragmentImpl():
           var element = interfaceFragment.element;
           if (!element.isDartCoreObject) {
-            if (interfaceFragment.supertype == null) {
+            if (element.supertype == null) {
               shouldResetClassHierarchies = true;
               element.supertype = objectType;
             }

pkg/linter/lib/src/rules/analyzer_public_api.dart

@@ -161,16 +161,13 @@ class _Visitor extends SimpleAstVisitor<void> {
         for (var typeParameter in typeParameters) {
           _checkTypeParameter(typeParameter, fragment: fragment);
         }
-        if (fragment case InterfaceFragment(
-          :var supertype,
-          :var interfaces,
-          :var mixins,
-        )) {
-          _checkType(supertype, fragment: fragment);
-          for (var t in interfaces) {
+        if (fragment is InterfaceFragment) {
+          var element = fragment.element;
+          _checkType(element.supertype, fragment: fragment);
+          for (var t in element.interfaces) {
             _checkType(t, fragment: fragment);
           }
-          for (var t in mixins) {
+          for (var t in element.mixins) {
             _checkType(t, fragment: fragment);
           }
         }