Implement type argument access and reification of runtime types.

pkg/compiler/lib/src/js_backend/codegen/codegen.dart

Index: pkg/compiler/lib/src/js_backend/codegen/codegen.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/codegen.dart b/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
index afa440bec33b65f56c0a90a43eeab57044668b4a..cf740e707344f772e645a0fd17feb5bc9d4c25c7 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
@@ -328,12 +328,6 @@ class CodeGenerator extends tree_ir.Visitor<dynamic, js.Expression> {
   }
 
   @override
-  js.Expression visitReifyTypeVar(tree_ir.ReifyTypeVar node) {
-    return giveup(node);
-    // TODO: implement visitReifyTypeVar
-  }
-
-  @override
   js.Expression visitThis(tree_ir.This node) {
     return new js.This();
   }
@@ -510,9 +504,49 @@ class CodeGenerator extends tree_ir.Visitor<dynamic, js.Expression> {
     visitStatement(node.next);
   }
 
+  js.Expression buildStaticHelperInvocation(FunctionElement helper,
+                                            List<js.Expression> arguments) {
+    registry.registerStaticUse(helper);
+    return buildStaticInvoke(new Selector.fromElement(helper), helper,
+        arguments);
+  }
+
+  @override
+  js.Expression visitReifyRuntimeType(tree_ir.ReifyRuntimeType node) {
+    FunctionElement createType = glue.getCreateRuntimeType();
+    FunctionElement typeToString = glue.getRuntimeTypeToString();
+    return buildStaticHelperInvocation(createType,
+        [buildStaticHelperInvocation(typeToString,
+            [visitExpression(node.value)])]);
+  }
+
+  @override
+  js.Expression visitReadTypeVariable(tree_ir.ReadTypeVariable node) {
+    if (node.context != node.variable.element.enclosingClass) {
+      giveup(node, 'substitution not implemented');

[asgerf, 2015/03/02 13:52:36]

I am confused. This should never happen because the context is always set to the
variable's enclosing class, and other the hand, some kind of substitution does
seem to be implemented below.

[karlklose, 2015/03/05 09:54:58]

Acknowledged.

+    }
+    js.Expression index = js.number(glue.getTypeVariableIndex(node.variable));
+    if (glue.needsSubstitutionForTypeVariableAccess(node.context)) {
+      js.Expression substitution = glue.getSubstitutionName(node.context);
+      return buildStaticHelperInvocation(
+          glue.getTypeArgumentWithSubstitution(),
+          [visitExpression(node.target), substitution, index]);
+    } else {
+      return buildStaticHelperInvocation(
+          glue.getTypeArgumentByIndex(),
+          [visitExpression(node.target), index]);
+    }
+  }
+
+
   // Dart-specific IR nodes
 
   @override
+  visitReifyTypeVar(tree_ir.ReifyTypeVar node) {
+    return errorUnsupportedNode(node);
+  }
+
+  @override
   visitFunctionExpression(tree_ir.FunctionExpression node) {
     return errorUnsupportedNode(node);
   }
@@ -532,7 +566,7 @@ class CodeGenerator extends tree_ir.Visitor<dynamic, js.Expression> {
     return errorUnsupportedNode(node);
   }
 
-  dynamic errorUnsupportedNode(tree_ir.DartSpecificNode node) {
+  errorUnsupportedNode(tree_ir.DartSpecificNode node) {
     throw "Unsupported node in JS backend: $node";
   }
 }