Disallow repeated type parameters (issues 2239 & 2240).

runtime/vm/parser.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/parser.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/compiler_stats.h"
@@ skipping 3124 matching lines @@
 
 
 void Parser::ParseTypeParameters(const Class& cls) {
   TRACE_PARSER("ParseTypeParameters");
   if (CurrentToken() == Token::kLT) {
     const GrowableObjectArray& type_parameters_array =
         GrowableObjectArray::Handle(GrowableObjectArray::New());
     const GrowableObjectArray& bounds_array =
         GrowableObjectArray::Handle(GrowableObjectArray::New());
     intptr_t index = 0;
-    AbstractType& type_parameter = TypeParameter::Handle();
+    TypeParameter& type_parameter = TypeParameter::Handle();
+    TypeParameter& existing_type_parameter = TypeParameter::Handle();
+    String& existing_type_parameter_name = String::Handle();
     AbstractType& bound = Type::Handle();
     do {
       ConsumeToken();
       if (CurrentToken() != Token::kIDENT) {
         ErrorMsg("type parameter name expected");
       }
       String& type_parameter_name = *CurrentLiteral();
       type_parameter = TypeParameter::New(cls,
                                           index,
                                           type_parameter_name,
                                           token_index_);
+      // Check that the type parameter is not repeated.
+      for (intptr_t i = 0; i < index; i++) {
+        existing_type_parameter ^= type_parameters_array.At(i);
+        existing_type_parameter_name = existing_type_parameter.Name();
+        if (existing_type_parameter_name.Equals(type_parameter_name)) {
+          ErrorMsg("repeated type parameter");
+        }
+      }
       ConsumeToken();
       bound = Type::DynamicType();
       if (CurrentToken() == Token::kEXTENDS) {
         ConsumeToken();
         // A bound may refer to the owner of the type parameter it applies to,
         // i.e. to the class or interface currently being parsed.
         // Postpone resolution in order to avoid resolving the class and its
         // type parameters, as they are not fully parsed yet.
         bound = ParseType(ClassFinalizer::kDoNotResolve);
       }
@@ skipping 5317 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart