Report a compile-time error when a setter has not exactly one formal parameter.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

 // 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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   DartType getType(Node node);
@@ skipping 3019 matching lines @@
           } else {
             compiler.onDeprecatedFeature(formalParameters, 'getter parameters');
           }
         }
       }
       LinkBuilder<Element> parametersBuilder =
         visitor.analyzeNodes(formalParameters.nodes);
       requiredParameterCount  = parametersBuilder.length;
       parameters = parametersBuilder.toLink();
     }
     DartType returnType = compiler.resolveReturnType(element, returnNode);

[ngeoffray, 2012/12/09 20:44:00]

This can move line 3050.

+    if (element.isSetter() && (requiredParameterCount != 1 ||
+                               visitor.optionalParameterCount != 0)) {
+      // If there are no formal parameters, we already reported an error above.

[ngeoffray, 2012/12/09 20:44:00]

Somehow this looks a bit brittle. Could you instead switch on the element kind
and report errors for each?

+      if (formalParameters != null) {
+        compiler.reportMessage(compiler.spanFromNode(formalParameters),
+                               MessageKind.ILLEGAL_SETTER_FORMALS.error([]),
+                               Diagnostic.ERROR);
+      }
+    }
     return new FunctionSignature(parameters,
                                  visitor.optionalParameters,
                                  requiredParameterCount,
                                  visitor.optionalParameterCount,
                                  visitor.optionalParametersAreNamed,
                                  returnType);
   }
 
   // TODO(ahe): This is temporary.
   void resolveExpression(Node node) {
@@ skipping 159 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }