Disallow repeated formal parameters (issue 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 1016 matching lines @@
     parameter.is_field_initializer = true;
   }
 
   // At this point, we must see an identifier for the parameter name.
   parameter.name_pos = token_index_;
   parameter.name = ExpectIdentifier("parameter name expected");
   if (parameter.is_field_initializer) {
     params->has_field_initializer = true;
   }
 
+  // Check that the formal parameter is not repeated.
+  const intptr_t num_existing_parameters =
+      params->num_fixed_parameters + params->num_optional_parameters;
+  for (intptr_t i = 0; i < num_existing_parameters; i++) {
+    ParamDesc& existing_parameter = (*params->parameters)[i];
+    if (existing_parameter.name->Equals(*parameter.name)) {
+      ErrorMsg(parameter.name_pos, "repeated formal parameter");

[hausner, 2012/05/23 21:34:39]

In other places we use the phrase "duplicate", so maybe the error should be
"duplicate formal parameter name" ? You could even include the parameter name.

+    }
+  }
+
   if (CurrentToken() == Token::kLPAREN) {
     // This parameter is probably a closure. If we saw the keyword 'var'
     // or 'final', a closure is not legal here and we ignore the
     // opening parens.
     if (!var_seen && !parameter.is_final) {
       // The parsed parameter type is actually the function result type.
       const AbstractType& result_type =
           AbstractType::Handle(parameter.type->raw());
 
       // Finish parsing the function type parameter.
@@ skipping 7447 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart