[cfe] Report error on conflict between setter and prefix

An error was never reported for conflict between a prefix and a setter declared in the same library.

Tests added for both the simple case and cases for enhanced parts.

Change-Id: I752d519840eac714be7f64307a610bb4db142ac4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/452120
Reviewed-by: Chloe Stefantsova <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>

Author: johnniwinther

pkg/front_end/lib/src/source/source_compilation_unit.dart

@@ -1422,7 +1422,6 @@ class SourceCompilationUnitImpl implements SourceCompilationUnit {
     int charOffset,
   ) {
     Builder? existing = prefixNameSpace.lookup(name)?.getable;
-    existing ??= libraryBuilder.libraryNameSpace.lookup(name)?.getable;
     if (existing is PrefixBuilder) {
       assert(existing.next is! PrefixBuilder);
       int? deferredFileOffset;
@@ -1449,7 +1448,11 @@ class SourceCompilationUnitImpl implements SourceCompilationUnit {
       }
       prefixFragment.builder = existing;
       return false;
-    } else if (existing != null) {
+    }
+
+    LookupResult? result = libraryBuilder.libraryNameSpace.lookup(name);
+    if (result != null) {
+      NamedBuilder existing = result.getable ?? result.setable!;
       String fullName = name;
       _problemReporting.addProblem(
         codeDuplicatedDeclaration.withArgumentsOld(fullName),
@@ -1467,6 +1470,7 @@ class SourceCompilationUnitImpl implements SourceCompilationUnit {
         ],
       );
     }
+
     _prefixNameSpace.addLocalMember(
       name,
       prefixFragment.createPrefixBuilder(

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart

@@ -0,0 +1,13 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part 'nested_part_declarations_part1.dart';
+part 'nested_part_declarations_part3.dart';
+
+void declaredInMain() {
+  declaredInMain();
+  declaredInPart1();
+  declaredInPart2();
+  declaredInPart3();
+}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart.strong.expect

@@ -0,0 +1,30 @@
+library;
+import self as self;
+
+part nested_part_declarations_part1.dart;
+part nested_part_declarations_part3.dart;
+part nested_part_declarations_part2.dart;
+static method declaredInMain() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part1.dart */ declaredInPart1() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part2.dart */ declaredInPart2() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part3.dart */ declaredInPart3() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart.strong.modular.expect

@@ -0,0 +1,30 @@
+library;
+import self as self;
+
+part nested_part_declarations_part1.dart;
+part nested_part_declarations_part3.dart;
+part nested_part_declarations_part2.dart;
+static method declaredInMain() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part1.dart */ declaredInPart1() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part2.dart */ declaredInPart2() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part3.dart */ declaredInPart3() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart.strong.outline.expect

@@ -0,0 +1,14 @@
+library;
+import self as self;
+
+part nested_part_declarations_part1.dart;
+part nested_part_declarations_part3.dart;
+part nested_part_declarations_part2.dart;
+static method declaredInMain() → void
+  ;
+static method /* from org-dartlang-testcase:///nested_part_declarations_part1.dart */ declaredInPart1() → void
+  ;
+static method /* from org-dartlang-testcase:///nested_part_declarations_part2.dart */ declaredInPart2() → void
+  ;
+static method /* from org-dartlang-testcase:///nested_part_declarations_part3.dart */ declaredInPart3() → void
+  ;

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart.strong.transformed.expect

@@ -0,0 +1,30 @@
+library;
+import self as self;
+
+part nested_part_declarations_part1.dart;
+part nested_part_declarations_part3.dart;
+part nested_part_declarations_part2.dart;
+static method declaredInMain() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part1.dart */ declaredInPart1() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part2.dart */ declaredInPart2() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}
+static method /* from org-dartlang-testcase:///nested_part_declarations_part3.dart */ declaredInPart3() → void {
+  self::declaredInMain();
+  self::declaredInPart1();
+  self::declaredInPart2();
+  self::declaredInPart3();
+}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart.textual_outline.expect

@@ -0,0 +1,5 @@
+part 'nested_part_declarations_part1.dart';
+
+part 'nested_part_declarations_part3.dart';
+
+void declaredInMain() {}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations.dart.textual_outline_modelled.expect

@@ -0,0 +1,5 @@
+part 'nested_part_declarations_part1.dart';
+
+part 'nested_part_declarations_part3.dart';
+
+void declaredInMain() {}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations_part1.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of 'nested_part_declarations.dart';
+
+part 'nested_part_declarations_part2.dart';
+
+void declaredInPart1() {
+  declaredInMain();
+  declaredInPart1();
+  declaredInPart2();
+  declaredInPart3();
+}

pkg/front_end/testcases/enhanced_parts/nested_part_declarations_part2.dart

@@ -0,0 +1,12 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of 'nested_part_declarations_part1.dart';
+
+void declaredInPart2() {
+  declaredInMain();
+  declaredInPart1();
+  declaredInPart2();
+  declaredInPart3();
+}