Write our JS blobs for handling native classes in Dart.

frog/leg/ssa/builder.dart

Index: frog/leg/ssa/builder.dart
===================================================================
--- frog/leg/ssa/builder.dart	(revision 5817)
+++ frog/leg/ssa/builder.dart	(working copy)
@@ -1854,11 +1854,17 @@
     link = link.tail.tail;
     List<HInstruction> inputs = <HInstruction>[];
     addGenericSendArgumentsToList(link, inputs);
-    LiteralString type = node.arguments.head;
-    LiteralString literal = node.arguments.tail.head;
-    compiler.ensure(literal is LiteralString);
-    compiler.ensure(type is LiteralString);
-    push(new HForeign(literal.dartString, type.dartString, inputs));
+    Node type = node.arguments.head;
+    Node literal = node.arguments.tail.head;
+    if (literal is !StringNode || literal.dynamic.isInterpolation) {
+      compiler.cancel('JS code must be a string literal', node: literal);
+    }
+    if (type is !LiteralString) {
+      compiler.cancel(
+          'The type of a JS expression must be a string literal', node: type);
+    }
+    push(new HForeign(
+        literal.dynamic.dartString, type.dynamic.dartString, inputs));
   }
 
   void handleForeignUnintercepted(Send node) {
@@ -1941,6 +1947,36 @@
     }
   }
 
+  void handleForeignDartClosureToJs(Send node) {
+    Node closure = node.arguments.head;
+    if (!node.arguments.tail.isEmpty()) {
+      compiler.cancel(
+          'Invalid number of arguments in JS_TO_CLOSURE',
+          node: node);
+    }
+    Element element = elements[closure];
+    if (!Elements.isStaticOrTopLevelFunction(element)) {
+      compiler.cancel(
+          'JS_TO_CLOSURE requires a static or top-level method',
+          node: closure);
+    }
+    FunctionElement function = element;
+    FunctionParameters parameters = element.computeParameters(compiler);
+    if (parameters.optionalParameterCount !== 0) {
+      compiler.cancel(
+          'JS_TO_CLOSURE does not handle closure with optional parameters',
+          node: closure);
+    }
+    visit(closure);
+    List<HInstruction> inputs = <HInstruction>[pop()];
+    String invocationName = compiler.namer.closureInvocationName(
+        new Selector(SelectorKind.INVOCATION,
+                     parameters.requiredParameterCount));
+    push(new HForeign(new SourceString('#.$invocationName'),
+                      const SourceString('var'),
+                      inputs));
+  }
+
   handleForeignSend(Send node) {
     Element element = elements[node];
     if (element === compiler.findHelper(const SourceString('JS'))) {
@@ -1957,6 +1993,9 @@
     } else if (element === compiler.findHelper(
           const SourceString('JS_CALL_IN_ISOLATE'))) {
       handleForeignJsCallInIsolate(node);
+    } else if (element === compiler.findHelper(
+          const SourceString('DART_CLOSURE_TO_JS'))) {
+      handleForeignDartClosureToJs(node);
     } else if (element === currentLibrary.find(const SourceString('native'))) {
       native.handleSsaNative(this, node);
     } else {