[analyzer] Report duplicate getter also if setter occurs first

Fixes #59977.

Change-Id: I83ea36ff6f30c33625e50628a3bb2392caac9400
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/434061
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Jens Johansen <[email protected]>

Author: jensjoha

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

@@ -615,6 +615,11 @@ class MemberDuplicateDefinitionVerifier {
             [name],
           ),
         );
+      } else {
+        // Getter setter pair. Make sure the *getter* is in the getter map.
+        if (element is PropertyAccessorFragmentImpl && element.isGetter) {
+          getterScope[name] = element;
+        }
       }
     } else {
       getterScope[name] = element;

pkg/analyzer/test/src/diagnostics/duplicate_definition_test.dart

@@ -274,6 +274,26 @@ augment class C {
     );
   }
 
+  test_instance_getter_getter_setter() async {
+    await assertErrorsInCode(
+      r'''
+class A {
+  int? get b => null;
+  int? get b => 0;
+  void set b(int? value) {}
+}
+''',
+      [
+        error(
+          CompileTimeErrorCode.DUPLICATE_DEFINITION,
+          43,
+          1,
+          contextMessages: [message(testFile, 21, 1)],
+        ),
+      ],
+    );
+  }
+
   test_instance_getter_method() async {
     await assertErrorsInCode(
       r'''
@@ -302,6 +322,46 @@ class C {
 ''');
   }
 
+  test_instance_getter_setter_getter() async {
+    await assertErrorsInCode(
+      r'''
+class A {
+  int? get b => null;
+  void set b(int? value) {}
+  int? get b => 0;
+}
+''',
+      [
+        error(
+          CompileTimeErrorCode.DUPLICATE_DEFINITION,
+          71,
+          1,
+          contextMessages: [message(testFile, 21, 1)],
+        ),
+      ],
+    );
+  }
+
+  test_instance_getter_setter_setter() async {
+    await assertErrorsInCode(
+      r'''
+class A {
+  int? get b => null;
+  void set b(int? value) {}
+  void set b(int? value) {}
+}
+''',
+      [
+        error(
+          CompileTimeErrorCode.DUPLICATE_DEFINITION,
+          71,
+          1,
+          contextMessages: [message(testFile, 43, 1)],
+        ),
+      ],
+    );
+  }
+
   test_instance_method_getter() async {
     await assertErrorsInCode(
       r'''
@@ -463,6 +523,46 @@ class C {
 ''');
   }
 
+  test_instance_setter_getter_getter() async {
+    await assertErrorsInCode(
+      r'''
+class A {
+  void set b(int? value) {}
+  int? get b => null;
+  int? get b => 0;
+}
+''',
+      [
+        error(
+          CompileTimeErrorCode.DUPLICATE_DEFINITION,
+          71,
+          1,
+          contextMessages: [message(testFile, 49, 1)],
+        ),
+      ],
+    );
+  }
+
+  test_instance_setter_getter_setter() async {
+    await assertErrorsInCode(
+      r'''
+class A {
+  void set b(int? value) {}
+  int? get b => null;
+  void set b(int? value) {}
+}
+''',
+      [
+        error(
+          CompileTimeErrorCode.DUPLICATE_DEFINITION,
+          71,
+          1,
+          contextMessages: [message(testFile, 21, 1)],
+        ),
+      ],
+    );
+  }
+
   test_instance_setter_method() async {
     await assertErrorsInCode(
       r'''
@@ -537,6 +637,26 @@ augment class C {
 ''');
   }
 
+  test_instance_setter_setter_getter() async {
+    await assertErrorsInCode(
+      r'''
+class A {
+  void set b(int? value) {}
+  void set b(int? value) {}
+  int? get b => null;
+}
+''',
+      [
+        error(
+          CompileTimeErrorCode.DUPLICATE_DEFINITION,
+          49,
+          1,
+          contextMessages: [message(testFile, 21, 1)],
+        ),
+      ],
+    );
+  }
+
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_instance_setter_setter_inAugmentation() async {
     await assertErrorsInCode(