diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
index d4c6a342dd5e..e5bffb313f84 100644
--- a/pkg/analyzer/lib/src/fasta/ast_builder.dart
+++ b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -1656,6 +1656,14 @@ class AstBuilder extends StackListener {
           rightParenthesis: rightParenthesis,
         );
       }
+      // Check for extension type name conflict.
+      var representationName = representation.fieldName;
+      if (representationName.lexeme == builder.name.lexeme) {
+        errorReporter.errorReporter?.reportErrorForToken(
+          ParserErrorCode.MEMBER_WITH_CLASS_NAME,
+          representationName,
+        );
+      }
       declarations.add(
         builder.build(
           typeKeyword: typeKeyword,
diff --git a/pkg/analyzer/test/src/dart/parser/extension_type_test.dart b/pkg/analyzer/test/src/dart/parser/extension_type_test.dart
index 3ace940083ba..c4e2b2211d1e 100644
--- a/pkg/analyzer/test/src/dart/parser/extension_type_test.dart
+++ b/pkg/analyzer/test/src/dart/parser/extension_type_test.dart
@@ -166,6 +166,31 @@ ExtensionTypeDeclaration
 ''');
   }
 
+  test_error_fieldName_asDeclaration() {
+    final parseResult = parseStringWithErrors(r'''
+extension type A(int A) {}
+''');
+    parseResult.assertErrors([
+      error(ParserErrorCode.MEMBER_WITH_CLASS_NAME, 21, 1),
+    ]);
+
+    final node = parseResult.findNode.singleExtensionTypeDeclaration;
+    assertParsedNodeText(node, r'''
+ExtensionTypeDeclaration
+  extensionKeyword: extension
+  typeKeyword: type
+  name: A
+  representation: RepresentationDeclaration
+    leftParenthesis: (
+    fieldType: NamedType
+      name: int
+    fieldName: A
+    rightParenthesis: )
+  leftBracket: {
+  rightBracket: }
+''');
+  }
+
   test_error_formalParameterModifier_covariant_method_instance() {
     final parseResult = parseStringWithErrors(r'''
 extension type A(int it) {