[analysis_server] RemoveLeadingUnderscore to handle conflicting names

Fixes #50142

Change-Id: I68c225e0528c643a29f2454607464d3896f25d36
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/262606
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: asashour

pkg/analysis_server/lib/src/services/correction/dart/remove_leading_underscore.dart

@@ -57,9 +57,22 @@ class RemoveLeadingUnderscore extends CorrectionProducer {
     // Find references to the identifier.
     List<SimpleIdentifier>? references;
     if (element is LocalVariableElement) {
-      var root = node.thisOrAncestorOfType<Block>();
-      if (root != null) {
-        references = findLocalElementReferences(root, element);
+      var block = node.thisOrAncestorOfType<Block>();
+      if (block != null) {
+        references = findLocalElementReferences(block, element);
+
+        var declaration = block.thisOrAncestorOfType<MethodDeclaration>() ??
+            block.thisOrAncestorOfType<FunctionDeclaration>();
+
+        if (declaration != null) {
+          if (isDeclaredIn(declaration, newName)) {
+            var suffix = -1;
+            do {
+              suffix++;
+            } while (isDeclaredIn(declaration, '$newName$suffix'));
+            newName = '$newName$suffix';
+          }
+        }
       }
     } else if (element is ParameterElement) {
       if (!element.isNamed) {

pkg/analysis_server/lib/src/services/correction/util.dart

@@ -466,6 +466,33 @@ bool hasDisplayName(Element? element, String name) {
   return element?.displayName == name;
 }
 
+/// Return whether the specified [name] is declared inside the [root] node
+/// or not.
+bool isDeclaredIn(AstNode root, String name) {
+  bool isDeclaredIn(FormalParameterList? parameters) {
+    if (parameters != null) {
+      for (var parameter in parameters.parameters) {
+        if (parameter.name?.lexeme == name) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  if (root is MethodDeclaration && isDeclaredIn(root.parameters)) {
+    return true;
+  }
+  if (root is FunctionDeclaration &&
+      isDeclaredIn(root.functionExpression.parameters)) {
+    return true;
+  }
+
+  var collector = _DeclarationCollector(name);
+  root.accept(collector);
+  return collector.isDeclared;
+}
+
 /// Checks if given [DartNode] is the left hand side of an assignment, or a
 /// declaration of a variable.
 bool isLeftHandOfAssignment(SimpleIdentifier node) {
@@ -1542,6 +1569,20 @@ class _CollectReferencedUnprefixedNames extends RecursiveAstVisitor {
   }
 }
 
+class _DeclarationCollector extends RecursiveAstVisitor<void> {
+  final String name;
+  bool isDeclared = false;
+
+  _DeclarationCollector(this.name);
+
+  @override
+  void visitVariableDeclaration(VariableDeclaration node) {
+    if (node.name.lexeme == name) {
+      isDeclared = true;
+    }
+  }
+}
+
 class _ElementReferenceCollector extends RecursiveAstVisitor<void> {
   final Element element;
   final List<SimpleIdentifier> references = [];

pkg/analysis_server/test/src/services/correction/fix/remove_leading_underscore_test.dart

@@ -89,6 +89,69 @@ void f() {
 ''');
   }
 
+  Future<void> test_localVariable_conflictWithParameter() async {
+    await resolveTestCode('''
+class A {
+  void m({int? foo}) {
+    var _foo = 1;
+    print(foo);
+    print(_foo);
+  }
+}
+''');
+    await assertHasFix('''
+class A {
+  void m({int? foo}) {
+    var foo0 = 1;
+    print(foo);
+    print(foo0);
+  }
+}
+''');
+  }
+
+  Future<void> test_localVariable_conflictWithVariable() async {
+    await resolveTestCode('''
+void f() {
+  var _foo = 1;
+  var foo = true;
+  print(_foo);
+  print(foo);
+}
+''');
+    await assertHasFix('''
+void f() {
+  var foo0 = 1;
+  var foo = true;
+  print(foo0);
+  print(foo);
+}
+''');
+  }
+
+  Future<void> test_localVariable_conflictWithVariable_existing() async {
+    await resolveTestCode('''
+void f() {
+  var _foo = 1;
+  var foo = true;
+  var foo0 = true;
+  print(_foo);
+  print(foo);
+  print(foo0);
+}
+''');
+    await assertHasFix('''
+void f() {
+  var foo1 = 1;
+  var foo = true;
+  var foo0 = true;
+  print(foo1);
+  print(foo);
+  print(foo0);
+}
+''');
+  }
+
   Future<void> test_parameter_closure() async {
     await resolveTestCode('''
 void f() {