Fixes #1681. Improve object pattern testing in a pattern assignment

LanguageFeatures/Patterns/object_A02_t12.dart

@@ -0,0 +1,31 @@
+// Copyright (c) 2023, 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.
+
+/// @assertion objectPattern ::= typeName typeArguments? '(' patternFields? ')'
+/// ...
+/// As with record patterns, the getter name can be omitted and inferred from
+/// the variable pattern in the field subpattern which may be wrapped in a unary
+/// pattern
+///
+/// @description Check that it is a compile-time error if an object pattern with
+/// the omitted getter name in a declaration context declares a variable that
+/// already exists
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns,records
+
+import "patterns_lib.dart";
+
+main() {
+  int areaAsInt = 1, sizeAsInt = 1;
+  var Square(:areaAsInt) = Square(1);
+//            ^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  var Square(: int sizeAsInt) = Square(2);
+//                 ^^^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified}
+}

LanguageFeatures/Patterns/pattern_assignment_A01_t05.dart

@@ -17,7 +17,7 @@
 /// @description Check an object pattern in a pattern assignment
 /// @author [email protected]
 
-// SharedOptions=--enable-experiment=patterns
+// SharedOptions=--enable-experiment=patterns,records
 
 import "../../Utils/expect.dart";
 import "patterns_lib.dart";
@@ -31,9 +31,4 @@ main() {
   Square(areaAsInt: a2, sizeAsInt: b2) = Square(2);
   Expect.equals(4, a2);
   Expect.equals(2, b2);
-
-  int areaAsInt = 5, sizeAsInt = 6;
-  var Square(:areaAsInt,: int sizeAsInt) = Square(3);
-  Expect.equals(9, areaAsInt);
-  Expect.equals(3, sizeAsInt);
 }