Ensure that function elements inside local variable elements have unique locations.

Fixes #44216.

Bug: #44216
Change-Id: I5ccf8bb5f90396eabfec470a289a193d2aef16ec
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/173881
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

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

@@ -4392,7 +4392,7 @@ class FunctionElementImpl extends ExecutableElementImpl
   String get identifier {
     String identifier = super.identifier;
     Element enclosing = enclosingElement;
-    if (enclosing is ExecutableElement) {
+    if (enclosing is ExecutableElement || enclosing is VariableElement) {
       identifier += "@$nameOffset";
     }
     return identifier;

pkg/analyzer/test/src/dart/element/element_test.dart

@@ -36,6 +36,7 @@ main() {
     defineReflectiveTests(ElementImplTest);
     defineReflectiveTests(LibraryElementImplTest);
     defineReflectiveTests(TopLevelVariableElementImplTest);
+    defineReflectiveTests(UniqueLocationTest);
   });
 }
 
@@ -2288,6 +2289,50 @@ class TypeParameterTypeImplTest extends AbstractTypeTest {
   }
 }
 
+@reflectiveTest
+class UniqueLocationTest extends PubPackageResolutionTest {
+  test_ambiguous_closure_in_executable() async {
+    await resolveTestCode('''
+void f() => [() => 0, () => 1];
+''');
+    expect(findNode.functionExpression('() => 0').declaredElement.location,
+        isNot(findNode.functionExpression('() => 1').declaredElement.location));
+  }
+
+  test_ambiguous_closure_in_local_variable() async {
+    await resolveTestCode('''
+void f() {
+  var x = [() => 0, () => 1];
+}
+''');
+    expect(findNode.functionExpression('() => 0').declaredElement.location,
+        isNot(findNode.functionExpression('() => 1').declaredElement.location));
+  }
+
+  test_ambiguous_closure_in_top_level_variable() async {
+    await resolveTestCode('''
+var x = [() => 0, () => 1];
+''');
+    expect(findNode.functionExpression('() => 0').declaredElement.location,
+        isNot(findNode.functionExpression('() => 1').declaredElement.location));
+  }
+
+  test_ambiguous_local_variable_in_executable() async {
+    await resolveTestCode('''
+f() {
+  {
+    int x = 0;
+  }
+  {
+    int x = 1;
+  }
+}
+''');
+    expect(findNode.variableDeclaration('x = 0').declaredElement.location,
+        isNot(findNode.variableDeclaration('x = 1').declaredElement.location));
+  }
+}
+
 @reflectiveTest
 class VoidTypeImplTest extends AbstractTypeTest {
   /// Reference {code VoidTypeImpl.getInstance()}.

pkg/nnbd_migration/test/api_test.dart

@@ -247,6 +247,28 @@ void main() {
     await _checkSingleFileChanges(content, expected);
   }
 
+  Future<void> test_ambiguous_closure_parameter_in_local_variable() async {
+    var content = '''
+Object f<T>(Object Function(T) callback, Object obj) => 0;
+g() {
+  var y = f<Map<String, int>>(
+      (x) => x.keys,
+      f<List<bool>>(
+          (x) => x.last, 0));
+}
+''';
+    var expected = '''
+Object f<T>(Object Function(T) callback, Object obj) => 0;
+g() {
+  var y = f<Map<String, int>>(
+      (x) => x.keys,
+      f<List<bool>>(
+          (x) => x.last, 0));
+}
+''';
+    await _checkSingleFileChanges(content, expected);
+  }
+
   Future<void> test_argumentError_checkNotNull_implies_non_null_intent() async {
     var content = '''
 void f(int i) {