Support lazy JS types.

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

Index: pkg/dev_compiler/lib/src/compiler/code_generator.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/code_generator.dart b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
index b7f3d5a048c61f3eb83779eb8979cf64a025c04e..361f5ec0198127d03ab3f0f684ebeaa356228e5d 100644
--- a/pkg/dev_compiler/lib/src/compiler/code_generator.dart
+++ b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
@@ -308,7 +308,8 @@ class CodeGenerator extends GeneralizingAstVisitor
   }
 
   List<String> _getJSName(Element e) {
-    if (findAnnotation(e.library, isPublicJSAnnotation) == null) {
+    if (e.library == null ||
+        findAnnotation(e.library, isPublicJSAnnotation) == null) {
       return null;
     }
 
@@ -322,6 +323,7 @@ class CodeGenerator extends GeneralizingAstVisitor
     if (findAnnotation(e, isPublicJSAnnotation) != null) {
       elementJSName = getAnnotationName(e, isPublicJSAnnotation) ?? '';
     }
+
     if (e is TopLevelVariableElement &&
         e.getter != null &&
         (e.getter.isExternal ||
@@ -2705,11 +2707,8 @@ class CodeGenerator extends GeneralizingAstVisitor
       var type = element.enclosingElement.type;
       var member = _emitMemberName(name, isStatic: isStatic, type: type);
 
-      // For static methods, we add the raw type name, without generics or
-      // library prefix. We don't need those because static calls can't use
-      // the generic type.
       if (isStatic) {
-        var dynType = _emitType(fillDynamicTypeArgs(type));
+        var dynType = _emitStaticAccess(type);
         return new JS.PropertyAccess(dynType, member);
       }
 
@@ -2908,6 +2907,40 @@ class CodeGenerator extends GeneralizingAstVisitor
     return typeParts;
   }
 
+  /// Emits an expression that lets you access statics on a [type] from code.
+  ///
+  /// If [nameType] is true, then the type will be named.  In addition,
+  /// if [hoistType] is true, then the named type will be hoisted.
+  JS.Expression _emitConstructorAccess(DartType type,
+      {bool nameType: true, bool hoistType: true}) {
+    return _emitJSInterop(type.element) ??
+        _emitType(type, nameType: nameType, hoistType: hoistType);
+  }
+
+  /// Emits an expression that lets you access statics on a [type] from code.
+  JS.Expression _emitStaticAccess(DartType type) {
+    // Make sure we aren't attempting to emit a static access path to a type
+    // that does not have a valid static access path.
+    assert(!type.isVoid &&
+        !type.isDynamic &&
+        !type.isBottom &&
+        type is! TypeParameterType);
+
+    // For statics, we add the raw type name, without generics or
+    // library prefix. We don't need those because static calls can't use
+    // the generic type.
+    type = fillDynamicTypeArgs(type);
+    var element = type.element;
+    _declareBeforeUse(element);
+
+    var interop = _emitJSInterop(element);
+    if (interop != null) return interop;
+
+    assert(type.name != '' && type.name != null);
+
+    return _emitTopLevelNameNoInterop(element);
+  }
+
   /// Emits a Dart [type] into code.
   ///
   /// If [lowerTypedef] is set, a typedef will be expanded as if it were a
@@ -2937,13 +2970,37 @@ class CodeGenerator extends GeneralizingAstVisitor
       return _callHelper('bottom');
     }
 
-    _declareBeforeUse(type.element);
+    var element = type.element;
+    _declareBeforeUse(element);
+
+    var interop = _emitJSInterop(element);
+    // Type parameters don't matter as JS interop types cannot be reified.
+    // We have to use lazy JS types because until we have proper module
+    // loading for JS libraries bundled with Dart libraries, we will sometimes
+    // need to load Dart libraries before the corresponding JS libraries are
+    // actually loaded.
+    // Given a JS type such as:
+    //     @JS('google.maps.Location')
+    //     class Location { ... }
+    // We can't emit a reference to MyType because the JS library that defines
+    // it may be loaded after our code. So for now, we use a special lazy type
+    // object to represent MyType.
+    // Anonymous JS types do not have a corresponding concrete JS type so we
+    // have to use a helper to define them.
+    if (interop != null) {
+      if (_isObjectLiteral(element)) {
+        return _callHelper(
+            'lazyAnonymousJSType(#)', js.string(element.displayName));
+      } else {
+        return _callHelper('lazyJSType(() => #, #)',
+            [interop, js.string(_getJSName(element).join('.'))]);
+      }
+    }
 
     // TODO(jmesserly): like constants, should we hoist function types out of
     // methods? Similar issue with generic types. For all of these, we may want
     // to canonicalize them too, at least when inside the same library.
     var name = type.name;
-    var element = type.element;
     if (name == '' || name == null || lowerTypedef) {
       // TODO(jmesserly): should we change how typedefs work? They currently
       // go through use similar logic as generic classes. This makes them
@@ -2957,9 +3014,7 @@ class CodeGenerator extends GeneralizingAstVisitor
       return new JS.Identifier(name);
     }
 
-    if (type == subClass?.type) {
-      return className;
-    }
+    if (type == subClass?.type) return className;
 
     if (type is ParameterizedType) {
       var args = type.typeArguments;
@@ -2982,12 +3037,16 @@ class CodeGenerator extends GeneralizingAstVisitor
       }
     }
 
-    return _emitTopLevelName(element);
+    return _emitTopLevelNameNoInterop(element);
   }
 
   JS.PropertyAccess _emitTopLevelName(Element e, {String suffix: ''}) {
     var interop = _emitJSInterop(e);
     if (interop != null) return interop;
+    return _emitTopLevelNameNoInterop(e, suffix: suffix);
+  }
+
+  JS.PropertyAccess _emitTopLevelNameNoInterop(Element e, {String suffix: ''}) {
     String name = getJSExportName(e) + suffix;
     return new JS.PropertyAccess(
         emitLibraryName(e.library), _propertyName(name));
@@ -3211,7 +3270,7 @@ class CodeGenerator extends GeneralizingAstVisitor
     // the generic type.
     ClassElement classElement = element.enclosingElement;
     var type = classElement.type;
-    var dynType = _emitType(fillDynamicTypeArgs(type));
+    var dynType = _emitStaticAccess(type);
     var member = _emitMemberName(element.name, isStatic: true, type: type);
     return _visit(rhs).toAssignExpression(
         annotate(new JS.PropertyAccess(dynType, member), lhs));
@@ -3362,6 +3421,19 @@ class CodeGenerator extends GeneralizingAstVisitor
     return helperMethodName;
   }
 
+  JS.Expression _emitTarget(Expression target, Element element, bool isStatic) {
+    if (isStatic) {
+      if (element is ConstructorElement) {
+        return _emitConstructorAccess(element.enclosingElement.type);
+      }
+      if (element is ExecutableElement) {
+        return _emitStaticAccess(
+            (element.enclosingElement as ClassElement).type);
+      }
+    }
+    return _visit(target);
+  }
+
   /// Emits a (possibly generic) instance method call.
   JS.Expression _emitMethodCallInternal(
       Expression target,
@@ -3374,7 +3446,7 @@ class CodeGenerator extends GeneralizingAstVisitor
     bool isStatic = element is ExecutableElement && element.isStatic;
     var memberName = _emitMemberName(name, type: type, isStatic: isStatic);
 
-    JS.Expression jsTarget = _visit(target);
+    JS.Expression jsTarget = _emitTarget(target, element, isStatic);
     if (isDynamicInvoke(target) || isDynamicInvoke(node.methodName)) {
       if (_inWhitelistCode(target)) {
         var vars = <JS.MetaLetVariable, JS.Expression>{};
@@ -3899,7 +3971,7 @@ class CodeGenerator extends GeneralizingAstVisitor
     var classElem = element.enclosingElement;
     var interop = _emitJSInterop(classElem);
     if (interop != null) return interop;
-    var typeName = _emitType(type);
+    var typeName = _emitConstructorAccess(type);
     if (name != null || element.isFactory) {
       var namedCtor = _constructorName(element);
       return new JS.PropertyAccess(typeName, namedCtor);
@@ -3925,7 +3997,7 @@ class CodeGenerator extends GeneralizingAstVisitor
       if (element == null) {
         // TODO(jmesserly): this only happens if we had a static error.
         // Should we generate a throw instead?
-        ctor = _emitType(type,
+        ctor = _emitConstructorAccess(type,
             nameType: options.hoistInstanceCreation,
             hoistType: options.hoistInstanceCreation);
         if (name != null) {
@@ -4749,7 +4821,7 @@ class CodeGenerator extends GeneralizingAstVisitor
           [_emitDynamicOperationName('dload'), _visit(target), name]);
     }
 
-    var jsTarget = _visit(target);
+    var jsTarget = _emitTarget(target, member, isStatic);
     bool isSuper = jsTarget is JS.Super;
 
     if (isSuper && member is FieldElement && !member.isSynthetic) {
@@ -5123,7 +5195,8 @@ class CodeGenerator extends GeneralizingAstVisitor
       // TODO(vsm): When we canonicalize, we need to treat private symbols
       // correctly.
       var name = js.string(node.components.join('.'), "'");
-      return js.call('#.new(#)', [_emitType(types.symbolType), name]);
+      return js
+          .call('#.new(#)', [_emitConstructorAccess(types.symbolType), name]);
     }
 
     return _emitConst(emitSymbol);