Check arguments counts.

sdk/lib/_internal/compiler/implementation/dart_types.dart

Index: sdk/lib/_internal/compiler/implementation/dart_types.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_types.dart b/sdk/lib/_internal/compiler/implementation/dart_types.dart
index 18c1b36f931edb3efbb9b42169e920d35011d4e7..7c78bd5a567f20682c5c7c07cfbe70d85478d8ab 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_types.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_types.dart
@@ -466,6 +466,19 @@ class FunctionType extends DartType {
 
   TypeKind get kind => TypeKind.FUNCTION;
 
+  DartType getNamedParameterType(SourceString name) {
+    Link<SourceString> namedParameter = namedParameters;
+    Link<DartType> namedParameterType = namedParameterTypes;
+    while (!namedParameter.isEmpty && !namedParameterType.isEmpty) {
+      if (namedParameter.head == name) {
+        return namedParameterType.head;
+      }
+      namedParameter = namedParameter.tail;
+      namedParameterType = namedParameterType.tail;
+    }
+    return null;
+  }
+
   DartType subst(Link<DartType> arguments, Link<DartType> parameters) {
     if (parameters.isEmpty) {
       assert(arguments.isEmpty);