Disallow repeated formal parameters (issue 2240).

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 7923)
+++ runtime/vm/parser.cc	(working copy)
@@ -1034,6 +1034,16 @@
     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