[DAS] Fixes completion suggestion for setter based on inheritance

[email protected]

Bug: #60298
Change-Id: I43b89744c74bd3bbfc664a505c0fc4d05cc87f5e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/414920
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Auto-Submit: Felipe Morschel <[email protected]>

Author: FMorschel

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

@@ -1076,7 +1076,7 @@ class DeclarationHelper {
     var referencingInterface = _referencingInterfaceFor(type.element3);
     for (var entry in membersByName.entries) {
       var members = entry.value;
-      var rawMember = members.bestMember;
+      var rawMember = _bestMember(members);
       if (rawMember is MethodElement) {
         if (includeMethods) {
           if (rawMember.isOperator) {
@@ -1505,6 +1505,54 @@ class DeclarationHelper {
     }
   }
 
+  /// Returns the element in [list] that is the best element to suggest.
+  ///
+  /// - If [mustBeAssignable] is `true` we look for the first setter:
+  ///   - If the setter is synthetic and contains a corresponding getter, we
+  ///     return the getter.
+  ///   - Otherwise, we return the setter.
+  /// - If [mustBeAssignable] is `false` or if there is no setter that meets the
+  ///   above criteria, we return the first getter.
+  /// - If the above are not possible, the first element in the list is
+  ///   returned under the assumption that it's lower in the hierarchy.
+  ExecutableElement _bestMember(List<ExecutableElement> list) {
+    var firstMember = list.first;
+    if (mustBeAssignable) {
+      if (firstMember case SetterElementImpl(
+        :var isSynthetic,
+        :var correspondingGetter2,
+      )) {
+        if (isSynthetic && correspondingGetter2 != null) {
+          return correspondingGetter2;
+        } else {
+          return firstMember;
+        }
+      }
+      for (var i = 1; i < list.length; i++) {
+        var member = list[i];
+        if (member case SetterElementImpl(
+          :var isSynthetic,
+          :var correspondingGetter2,
+        )) {
+          if (isSynthetic && correspondingGetter2 != null) {
+            return correspondingGetter2;
+          } else {
+            return member;
+          }
+        }
+      }
+    }
+    if (firstMember is SetterElement) {
+      for (var i = 1; i < list.length; i++) {
+        var member = list[i];
+        if (member is GetterElement) {
+          return member;
+        }
+      }
+    }
+    return firstMember;
+  }
+
   bool _canAccessInstanceMember(ExecutableElement element) {
     if (element.isStatic) {
       return false;
@@ -2535,25 +2583,6 @@ extension on Element {
   }
 }
 
-extension on List<ExecutableElement> {
-  /// Returns the element in this list that is the best element to suggest.
-  ///
-  /// Getters are preferred over setters, otherwise the first element in the
-  /// list is returned under the assumption that it's lower in the hierarchy.
-  ExecutableElement get bestMember {
-    ExecutableElement bestMember = this[0];
-    if (bestMember is SetterElement) {
-      for (var i = 1; i < length; i++) {
-        var member = this[i];
-        if (member is GetterElement) {
-          return member;
-        }
-      }
-    }
-    return bestMember;
-  }
-}
-
 extension on PropertyAccessorElement {
   /// Whether this accessor is an accessor for a constant variable.
   bool get isConst {

pkg/analysis_server/test/services/completion/dart/declaration/class_member_test.dart

@@ -21,6 +21,61 @@ mixin ClassMemberTestCases on AbstractCompletionDriverTest {
   @override
   bool get includeKeywords => false;
 
+  Future<void> test_abstractImplementation_missing() async {
+    await computeSuggestions('''
+class A {
+  A? v1;
+}
+
+class O extends A {}
+
+abstract class A2 implements A {
+  @override
+  O? get v1;
+}
+
+void f(A2 p) {
+  p.^ = null;
+}
+''');
+    assertResponse(r'''
+suggestions
+  v1
+    kind: field
+''');
+  }
+
+  Future<void> test_abstractImplementation_missing2() async {
+    await computeSuggestions('''
+class A {
+  A? get v1;
+}
+
+class O extends A {}
+
+class O2 extends O {}
+
+abstract class A2 implements A {
+  @override
+  O? v1;
+}
+
+abstract class A3 implements A2 {
+  @override
+  O2? get v1;
+}
+
+void f(A3 p) {
+  p.^ = null;
+}
+''');
+    assertResponse(r'''
+suggestions
+  v1
+    kind: field
+''');
+  }
+
   Future<void> test_inheritedFromPrivateClass() async {
     newFile('$testPackageLibPath/b.dart', '''
 library B;