Make method overrides with differing parameters a compile-time error

compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java

Index: compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
diff --git a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
index cb3b360b243223821d7f7ebe3d35926c89c213fe..9b219e567a598cfe1d70ea6037cfea9d57c59884 100644
--- a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
+++ b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
@@ -741,7 +741,7 @@ public class TypeAnalyzer implements DartCompilationPhase {
               sb);
         }
       }
-      // Finish current class. 
+      // Finish current class.
       setCurrentClass(null);
       return type;
     }
@@ -1693,23 +1693,26 @@ public class TypeAnalyzer implements DartCompilationPhase {
       }
 
       /**
-       * Report a static type error if member cannot override superElement, that is, they are not
-       * assignable.
+       * Report a static type error if member cannot override superElement, that
+       * is, they are not assignable.
        */
       private void checkOverride(DartExpression node, Element member, Element superElement) {
         String name = member.getName();
         Type superMember = typeAsMemberOf(superElement, currentClass);
-        if (member.getKind() == ElementKind.METHOD
-            && superElement.getKind() == ElementKind.METHOD) {
+        if (member.getKind() == ElementKind.METHOD && superElement.getKind() == ElementKind.METHOD) {
           if (!types.isSubtype(member.getType(), superMember)) {
-            typeError(node, TypeErrorCode.CANNOT_OVERRIDE_METHOD_NOT_SUBTYPE,
-                      name, superElement.getEnclosingElement().getName(),
-                      member.getType(), superMember);
+            MethodElement method = (MethodElement) member;
+            MethodElement superMethod = (MethodElement) superElement;
+            // Wrong # of parameters is a compile-time error and has already
+            // been checked.
+            if (method.getParameters().size() == superMethod.getParameters().size()) {
+              typeError(node, TypeErrorCode.CANNOT_OVERRIDE_METHOD_NOT_SUBTYPE, name, superElement
+                  .getEnclosingElement().getName(), member.getType(), superMember);
+            }
           }
         } else if (!types.isAssignable(superMember, member.getType())) {
-          typeError(node, TypeErrorCode.CANNOT_OVERRIDE_TYPED_MEMBER,
-                    name, superElement.getEnclosingElement().getName(),
-                    member.getType(), superMember);
+          typeError(node, TypeErrorCode.CANNOT_OVERRIDE_TYPED_MEMBER, name, superElement
+              .getEnclosingElement().getName(), member.getType(), superMember);
         }
       }
     }