Introduces the new syntax for deferred loading

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

Index: sdk/lib/_internal/compiler/implementation/elements/modelx.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/modelx.dart b/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
index eb48b99e04a22800f2bd563b2ab8db66228b09dc..480f3f6bdf6b3222b3d859fd5a3d2c56a1d94ec2 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
@@ -76,6 +76,7 @@ abstract class ElementX implements Element {
     return enclosingElement != null && enclosingElement.isClass();
   }
   bool isInstanceMember() => false;
+  bool isDeferredLoaderFunction() => false;
 
   bool isFactoryConstructor() => modifiers.isFactory();
   bool isGenerativeConstructor() =>
@@ -1027,6 +1028,10 @@ class PrefixElementX extends ElementX implements PrefixElement {
 
   bool isDeferred = false;
 
+  // Only needed for deferred imports.
+  Import _import;

[floitsch, 2014/03/17 14:15:41]

I don't really like this.

Every prefix comes from imports. Having a field that only works in special
circumstances feels wrong.
Could we have a list of imports, and a `singleImport` that throws if there is
more than one?

[Johnni Winther, 2014/03/18 12:29:14]

Or rename to `deferredImport` ?

[sigurdm, 2014/03/19 12:46:30]

Done.

+  Import get import => _import;
+
   PrefixElementX(String prefix, Element enclosing, this.firstPosition)
       : super(prefix, ElementKind.PREFIX, enclosing);
 
@@ -1042,8 +1047,9 @@ class PrefixElementX extends ElementX implements PrefixElement {
 
   accept(ElementVisitor visitor) => visitor.visitPrefixElement(this);
 
-  void markAsDeferred() {
+  void markAsDeferred(Import import) {
     isDeferred = true;
+    _import = import;
   }
 }
 
@@ -1655,6 +1661,33 @@ class FunctionElementX extends ElementX with AnalyzableElement
   accept(ElementVisitor visitor) => visitor.visitFunctionElement(this);
 }
 
+class DeferredLoaderFunctionElementX extends FunctionElementX {

[karlklose, 2014/03/17 14:05:00]

This element should have source code information.

When, for example, calling it with too many arguments, we may print a hint and
then we would need the source code location to point to.

[sigurdm, 2014/03/19 12:46:30]

Done.

+  PrefixElement prefix;
+  DeferredLoaderFunctionElementX(prefix)

[karlklose, 2014/03/17 14:05:00]

`prefix` -> `this.prefix`.

[sigurdm, 2014/03/19 12:46:30]

Not fixed - we still need to pass on the prefix to super.

+      : prefix = prefix,
+        super("loadLibrary",
+              ElementKind.FUNCTION,
+              Modifiers.EMPTY,
+              prefix, true);
+
+  FunctionSignature computeSignature(Compiler compiler) {
+    if (functionSignature != null) return functionSignature;
+    compiler.withCurrentElement(this, () {
+      functionSignature = new FunctionSignatureX(const Link(),
+          const Link(), 0, 0, false, compiler.types.dynamicType);
+    });
+    return functionSignature;
+  }
+
+  bool isMember() => false;
+
+  bool get isSynthesized => true;
+
+  bool isForeign(Compiler compiler) => true;
+
+  bool isDeferredLoaderFunction() => true;
+}
+
 class ConstructorBodyElementX extends FunctionElementX
     implements ConstructorBodyElement {
   FunctionElement constructor;