analyzer: Report duplicate unnamed and "new"-named constructors

Bug: #46020
Change-Id: I5a737b8b227fa205e66650dd40d697e4e3ef0125
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/208821
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>

Author: srawlins

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

@@ -253,15 +253,18 @@ class DuplicateDefinitionVerifier {
 
   /// Check that there are no members with the same name.
   void _checkClassMembers(ClassElement element, List<ClassMember> members) {
-    Set<String> constructorNames = HashSet<String>();
-    Map<String, Element> instanceGetters = HashMap<String, Element>();
-    Map<String, Element> instanceSetters = HashMap<String, Element>();
-    Map<String, Element> staticGetters = HashMap<String, Element>();
-    Map<String, Element> staticSetters = HashMap<String, Element>();
+    var constructorNames = HashSet<String>();
+    var instanceGetters = HashMap<String, Element>();
+    var instanceSetters = HashMap<String, Element>();
+    var staticGetters = HashMap<String, Element>();
+    var staticSetters = HashMap<String, Element>();
 
     for (ClassMember member in members) {
       if (member is ConstructorDeclaration) {
         var name = member.name?.name ?? '';
+        if (name == 'new') {
+          name = '';
+        }
         if (!constructorNames.add(name)) {
           if (name.isEmpty) {
             _errorReporter.reportErrorForName(

pkg/analyzer/test/src/dart/resolution/class_test.dart

@@ -338,6 +338,28 @@ class C {
     ]);
   }
 
+  test_error_duplicateConstructorDefault_bothNew() async {
+    await assertErrorsInCode(r'''
+class C {
+  C.new();
+  C.new();
+}
+''', [
+      error(CompileTimeErrorCode.DUPLICATE_CONSTRUCTOR_DEFAULT, 23, 5),
+    ]);
+  }
+
+  test_error_duplicateConstructorDefault_oneNew() async {
+    await assertErrorsInCode(r'''
+class C {
+  C();
+  C.new();
+}
+''', [
+      error(CompileTimeErrorCode.DUPLICATE_CONSTRUCTOR_DEFAULT, 19, 5),
+    ]);
+  }
+
   test_error_duplicateConstructorName() async {
     await assertErrorsInCode(r'''
 class C {