Get the basics of deferred libraries working.

pkg/dev_compiler/lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 3256 matching lines @@
     return new JS.Block(stmts);
   }
 
   @override
   JS.Block visitBlock(Block node) =>
       new JS.Block(_visitList(node.statements) as List<JS.Statement>,
           isScope: true);
 
   @override
   visitMethodInvocation(MethodInvocation node) {
+    if (_isDeferredLoadLibrary(node.target, node.methodName)) {
+      // We are calling loadLibrary() on a deferred library prefix.
+      return _callHelper('loadLibrary()');
+    }
+
     if (node.operator?.lexeme == '?.') {
       return _emitNullSafe(node);
     }
 
     var result = _emitForeignJS(node);
     if (result != null) return result;
 
     var target = _getTarget(node);
     if (target == null || isLibraryPrefix(target)) {
       return _emitFunctionCall(node);
@@ skipping 1247 matching lines @@
   }
 
   @override
   JS.This visitThisExpression(ThisExpression node) => new JS.This();
 
   @override
   JS.Super visitSuperExpression(SuperExpression node) => new JS.Super();
 
   @override
   visitPrefixedIdentifier(PrefixedIdentifier node) {
+    if (_isDeferredLoadLibrary(node.prefix, node.identifier)) {
+      // We are tearing off "loadLibrary" on a library prefix.
+      return _callHelper('loadLibrary');
+    }
+
     if (isLibraryPrefix(node.prefix)) {
       return _visit(node.identifier);
     } else {
       return _emitAccess(node.prefix, node.identifier, node.staticType);
     }
   }
 
   @override
   visitPropertyAccess(PropertyAccess node) {
     if (node.operator.lexeme == '?.') {
@@ skipping 1017 matching lines @@
 }
 
 bool isLibraryPrefix(Expression node) =>
     node is SimpleIdentifier && node.staticElement is PrefixElement;
 
 LibraryElement _getLibrary(AnalysisContext c, String uri) =>
     c.computeLibraryElement(c.sourceFactory.forUri(uri));
 
 bool _isDartRuntime(LibraryElement l) =>
     l.isInSdk && l.source.uri.toString() == 'dart:_runtime';
+
+/// Returns `true` if [target] is a prefix for a deferred library and [name]
+/// is "loadLibrary".
+///
+/// If so, the expression should be compiled to call the runtime's
+/// "loadLibrary" helper function.
+bool _isDeferredLoadLibrary(Expression target, SimpleIdentifier name) {
+  if (name.name != "loadLibrary") return false;
+
+  if (target is! SimpleIdentifier) return false;
+  var targetIdentifier = target as SimpleIdentifier;
+
+  if (targetIdentifier.staticElement is! PrefixElement) return false;
+  var prefix = targetIdentifier.staticElement as PrefixElement;
+
+  // The library the prefix is referring to must come from a deferred import.
+  var containingLibrary = (target.root as CompilationUnit).element.library;
+  var imports = containingLibrary.getImportsWithPrefix(prefix);
+  return imports.length == 1 && imports[0].isDeferred;
+}