Add deferred loading to Kernel.

pkg/compiler/lib/src/kernel/kernel_visitor.dart

Index: pkg/compiler/lib/src/kernel/kernel_visitor.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel_visitor.dart b/pkg/compiler/lib/src/kernel/kernel_visitor.dart
index 8ba98d0bea7888a493cd276aa5633eabf2f41ff5..f947a3f247d06f498b39de8e6e96385fbeba7574 100644
--- a/pkg/compiler/lib/src/kernel/kernel_visitor.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_visitor.dart
@@ -214,6 +214,10 @@ class KernelVisitor extends Object
 
   bool isVoidContext = false;
 
+  /// If non-null, reference to a deferred library that a subsequent getter is
+  /// using.
+  ir.DeferredImport _deferredLibrary;
+
   KernelVisitor(this.currentElement, this.elements, this.kernel);
 
   KernelVisitor get sendVisitor => this;
@@ -363,7 +367,16 @@ class KernelVisitor extends Object
   }
 
   @override
-  void previsitDeferredAccess(Send node, PrefixElement prefix, _) {}
+  void previsitDeferredAccess(Send node, PrefixElement prefix, _) {
+    // This is visited before any element access, and if it is deferred,
+    // prefix.isDeferred = true.
+    if (prefix != null && prefix.isDeferred) {
+      _deferredLibrary = new ir.DeferredImport(
+          kernel.libraries[prefix.deferredImport.importedLibrary], prefix.name);
+    } else {
+      _deferredLibrary = null;
+    }
+  }
 
   @override
   internalError(Spannable spannable, String message) {
@@ -1994,7 +2007,14 @@ class KernelVisitor extends Object
   }
 
   ir.Expression buildStaticGet(Element element) {
-    return buildStaticAccessor(element).buildSimpleRead();
+    var expression = buildStaticAccessor(element).buildSimpleRead();
+    if (_deferredLibrary != null) {
+      ir.Let let = new ir.Let(
+          makeOrReuseVariable(new ir.CheckLibraryIsLoaded(_deferredLibrary)),
+          expression);
+      return let;
+    }
+    return expression;
   }
 
   @override
@@ -2232,21 +2252,31 @@ class KernelVisitor extends Object
   @override
   ir.Expression handleStaticGetterGet(Send node, FunctionElement getter, _) {
     if (getter.isDeferredLoaderGetter) {
-      // TODO(ahe): Support deferred load.
-      return new ir.InvalidExpression();
+      // This is the LoadLibrary call.
+      var deferredLibrary = new ir.DeferredImport(

[sra1, 2017/02/14 03:14:06]

I would expect there to be a single shared DeferredImport.
There is a list of them in the Library.
How to they get added there?

[Emily Fortuna, 2017/02/14 20:56:28]

Changed to PutIfAbsent. I'm not convinced this is an improvement though. It adds
a whole bunch of checks.

+          kernel.libraries[getter.prefix.deferredImport.importedLibrary],
+          getter.prefix.name);
+      assert(deferredLibrary != null);
+      return new ir.LoadLibrary(deferredLibrary);
     }
-    return buildStaticGet(getter);
+    var expression = buildStaticGet(getter);
+    return expression;
   }
 
   @override
   ir.Expression handleStaticGetterInvoke(Send node, FunctionElement getter,
       NodeList arguments, CallStructure callStructure, _) {
+    var expression;
     if (getter.isDeferredLoaderGetter) {
-      // TODO(ahe): Support deferred load.
-      return new ir.InvalidExpression();
+      var deferredLibrary = new ir.DeferredImport(
+          kernel.libraries[getter.prefix.deferredImport.importedLibrary],
+          getter.prefix.name);
+      assert(deferredLibrary != null);
+      expression = new ir.LoadLibrary(deferredLibrary);

[sra1, 2017/02/14 03:14:06]

This code is the same as above.
I'd put it in a separate function so that if we threw our LoadLibrary and
directly make a js_runtime call, it would be in one place.

[Emily Fortuna, 2017/02/14 20:56:28]

done. See above.

+    } else {
+      expression = buildStaticGet(getter);
     }
-    return associateNode(
-        buildCall(buildStaticGet(getter), callStructure, arguments), node);
+    return associateNode(buildCall(expression, callStructure, arguments), node);
   }
 
   @override
@@ -2816,7 +2846,8 @@ class KernelVisitor extends Object
         if (currentElement.isGenerativeConstructor) {
           return buildGenerativeConstructor(currentElement, null, null);
         } else {
-          return internalError(currentElement, "Unhandled synthetic function.");
+          return internalError(currentElement,
+              "Unhandled synthetic function.");
         }
       } else {
         Node node = currentElement.node;