Support typedefs in function signatures.

sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart b/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
index f46526766fe5542a8136f4a43091a28d6ddf4522..cb4e509d5d91e9510b4699cb491457e946fd8441 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
@@ -13,6 +13,7 @@ abstract class TypeChecks {
 }
 
 typedef jsAst.Expression OnVariableCallback(TypeVariableType variable);
+typedef bool ShouldEncodeTypedefCallback(TypedefType variable);
 
 class RuntimeTypes {
   final Compiler compiler;
@@ -560,9 +561,12 @@ class RuntimeTypes {
     return jsAst.prettyPrint(representation, compiler).buffer.toString();
   }
 
-  jsAst.Expression getTypeRepresentation(DartType type,
-                                         OnVariableCallback onVariable) {
-    return representationGenerator.getTypeRepresentation(type, onVariable);
+  jsAst.Expression getTypeRepresentation(
+      DartType type,
+      OnVariableCallback onVariable,
+      [ShouldEncodeTypedefCallback shouldEncodeTypedef]) {
+    return representationGenerator.getTypeRepresentation(
+        type, onVariable, shouldEncodeTypedef);
   }
 
   bool isSimpleFunctionType(FunctionType type) {
@@ -606,6 +610,7 @@ class RuntimeTypes {
 class TypeRepresentationGenerator extends DartTypeVisitor {
   final Compiler compiler;
   OnVariableCallback onVariable;
+  ShouldEncodeTypedefCallback shouldEncodeTypedef;
 
   JavaScriptBackend get backend => compiler.backend;
   Namer get namer => backend.namer;
@@ -616,11 +621,16 @@ class TypeRepresentationGenerator extends DartTypeVisitor {
    * Creates a type representation for [type]. [onVariable] is called to provide
    * the type representation for type variables.
    */
-  jsAst.Expression getTypeRepresentation(DartType type,
-                                         OnVariableCallback onVariable) {
+  jsAst.Expression getTypeRepresentation(
+      DartType type,
+      OnVariableCallback onVariable,
+      ShouldEncodeTypedefCallback encodeTypedef) {
     this.onVariable = onVariable;
+    this.shouldEncodeTypedef =
+        (encodeTypedef != null) ? encodeTypedef : (TypedefType type) => false;
     jsAst.Expression representation = visit(type);
     this.onVariable = null;
+    this.shouldEncodeTypedef = null;
     return representation;
   }
 
@@ -629,7 +639,7 @@ class TypeRepresentationGenerator extends DartTypeVisitor {
   }
 
   visit(DartType type) {
-    return type.unalias(compiler).accept(this, null);
+    return type.accept(this, null);
   }
 
   visitTypeVariableType(TypeVariableType type, _) {
@@ -705,6 +715,25 @@ class TypeRepresentationGenerator extends DartTypeVisitor {
     return js('null');
   }
 
+  visitTypedefType(TypedefType type, _) {
+    bool shouldEncode = shouldEncodeTypedef(type);
+    DartType unaliasedType = type.unalias(compiler);
+    if (shouldEncode) {
+      jsAst.ObjectInitializer initializer = unaliasedType.accept(this, null);
+      // We have to encode the aliased type.
+      jsAst.Expression name = getJavaScriptClassName(type.element);
+      jsAst.Expression encodedTypedef =
+          type.treatAsRaw ? name : visitList(type.typeArguments, head: name);
+
+      // Add it to the function-type object.
+      jsAst.LiteralString tag = js.string(namer.typedefTag());
+      initializer.properties.add(new jsAst.Property(tag, encodedTypedef));
+      return initializer;
+    } else {
+      return unaliasedType.accept(this, null);
+    }
+  }
+
   visitType(DartType type, _) {
     compiler.internalError(NO_LOCATION_SPANNABLE,
         'Unexpected type: $type (${type.kind}).');