Remove unnecessary imports to tree.dart

R=het@google.com

Review URL: https://codereview.chromium.org/2203013003 .

pkg/compiler/lib/src/constant_system_dart.dart

@@ -8,7 +8,7 @@ import 'compiler.dart' show Compiler;
 import 'constants/constant_system.dart';
 import 'constants/values.dart';
 import 'dart_types.dart';
-import 'tree/tree.dart' show DartString;
+import 'tree/dartstring.dart' show DartString;
 
 const DART_CONSTANT_SYSTEM = const DartConstantSystem();
 

pkg/compiler/lib/src/constants/constant_system.dart

@@ -7,7 +7,7 @@ library dart2js.constant_system;
 import '../dart_types.dart';
 import '../compiler.dart' show Compiler;
 import '../resolution/operators.dart';
-import '../tree/tree.dart' show DartString;
+import '../tree/dartstring.dart' show DartString;
 import 'values.dart';
 
 abstract class Operation {

pkg/compiler/lib/src/constants/expressions.dart

@@ -16,7 +16,7 @@ import '../elements/elements.dart'
         PrefixElement,
         VariableElement;
 import '../resolution/operators.dart';
-import '../tree/tree.dart' show DartString;
+import '../tree/dartstring.dart' show DartString;
 import '../universe/call_structure.dart' show CallStructure;
 import 'evaluation.dart';
 import 'values.dart';

pkg/compiler/lib/src/constants/values.dart

@@ -9,7 +9,7 @@ import '../core_types.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart'
     show FieldElement, FunctionElement, PrefixElement;
-import '../tree/tree.dart' hide unparse;
+import '../tree/dartstring.dart';
 import '../util/util.dart' show Hashing;
 
 abstract class ConstantValueVisitor<R, A> {

pkg/compiler/lib/src/deferred_load.dart

@@ -36,7 +36,6 @@ import 'js_backend/js_backend.dart' show JavaScriptBackend;
 import 'resolution/resolution.dart' show AnalyzableElementX;
 import 'resolution/tree_elements.dart' show TreeElements;
 import 'tree/tree.dart' as ast;
-import 'tree/tree.dart' show Import, Node;
 import 'universe/use.dart' show StaticUse, TypeUse, TypeUseKind;
 import 'universe/world_impact.dart'
     show ImpactUseCase, WorldImpact, WorldImpactVisitorImpl;
@@ -93,8 +92,7 @@ class DeferredLoadTask extends CompilerTask {
   /// DeferredLibrary from dart:async
   ClassElement get deferredLibraryClass => compiler.deferredLibraryClass;
 
-  /// A synthetic [Import] representing the loading of the main
-  /// program.
+  /// A synthetic import representing the loading of the main program.
   final _DeferredImport _fakeMainImport = const _DeferredImport();
 
   /// The OutputUnit that will be loaded when the program starts.
@@ -235,7 +233,7 @@ class DeferredLoadTask extends CompilerTask {
     return imports.every((ImportElement import) => import.isDeferred);
   }
 
-  /// Returns a [Link] of every [Import] that imports [element] into [library].
+  /// Returns every [ImportElement] that imports [element] into [library].
   Iterable<ImportElement> _getImports(Element element, LibraryElement library) {
     if (element.isClassMember) {
       element = element.enclosingClass;
@@ -347,8 +345,8 @@ class DeferredLoadTask extends CompilerTask {
         // implicit constant expression are seen that we should be able to add
         // (like primitive constant literals like `true`, `"foo"` and `0`).
         // See dartbug.com/26406 for context.
-        treeElements
-            .forEachConstantNode((Node node, ConstantExpression expression) {
+        treeElements.forEachConstantNode(
+            (ast.Node node, ConstantExpression expression) {
           if (compiler.serialization.isDeserialized(analyzableElement)) {
             if (!expression.isImplicit && !expression.isPotential) {
               // Enforce evaluation of [expression].

pkg/compiler/lib/src/inferrer/type_graph_inferrer.dart

@@ -15,8 +15,8 @@ import '../dart_types.dart' show DartType;
 import '../elements/elements.dart';
 import '../js_backend/js_backend.dart' show Annotations, JavaScriptBackend;
 import '../resolution/tree_elements.dart' show TreeElementMapping;
-import '../tree/tree.dart' as ast
-    show DartString, Node, LiteralBool, TryStatement;
+import '../tree/tree.dart' as ast show Node, LiteralBool, TryStatement;
+import '../tree/dartstring.dart' show DartString;
 import '../types/constants.dart' show computeTypeMask;
 import '../types/types.dart'
     show ContainerTypeMask, MapTypeMask, TypeMask, TypesInferrer;
@@ -227,7 +227,7 @@ class TypeInformationSystem extends TypeSystem<TypeInformation> {
 
   TypeInformation nonNullEmptyType;
 
-  TypeInformation stringLiteralType(ast.DartString value) {
+  TypeInformation stringLiteralType(DartString value) {
     return new StringLiteralTypeInformation(
         value, compiler.typesTask.stringType);
   }

pkg/compiler/lib/src/inferrer/type_graph_nodes.dart

@@ -14,7 +14,8 @@ import '../cps_ir/cps_ir_nodes.dart' as cps_ir show Node;
 import '../dart_types.dart' show DartType, FunctionType, TypeKind;
 import '../elements/elements.dart';
 import '../native/native.dart' as native;
-import '../tree/tree.dart' as ast show DartString, Node, LiteralBool, Send;
+import '../tree/tree.dart' as ast show Node, LiteralBool, Send;
+import '../tree/dartstring.dart' show DartString;
 import '../types/types.dart'
     show
         ContainerTypeMask,
@@ -1209,7 +1210,7 @@ class ConcreteTypeInformation extends TypeInformation {
 }
 
 class StringLiteralTypeInformation extends ConcreteTypeInformation {
-  final ast.DartString value;
+  final DartString value;
 
   StringLiteralTypeInformation(value, TypeMask mask)
       : super(new ValueTypeMask(mask, new StringConstantValue(value))),

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

@@ -11,7 +11,7 @@ import '../constant_system_dart.dart';
 import '../core_types.dart' show CoreTypes;
 import '../dart_types.dart';
 import '../elements/elements.dart' show ClassElement, FieldElement;
-import '../tree/tree.dart' show DartString, LiteralDartString;
+import '../tree/dartstring.dart' show DartString, LiteralDartString;
 import 'js_backend.dart';
 
 const JAVA_SCRIPT_CONSTANT_SYSTEM = const JavaScriptConstantSystem();

pkg/compiler/lib/src/js_emitter/constant_ordering.dart

@@ -8,7 +8,7 @@ import '../constants/values.dart';
 
 import '../dart_types.dart';
 import '../elements/elements.dart' show Element, Elements, FieldElement;
-import '../tree/tree.dart' show DartString;
+import '../tree/dartstring.dart' show DartString;
 import '../js_backend/js_backend.dart' show SyntheticConstantKind;
 
 /// A canonical but arbrary ordering of constants. The ordering is 'stable'

pkg/compiler/lib/src/ssa/optimize.dart

@@ -14,7 +14,7 @@ import '../js/js.dart' as js;
 import '../js_backend/backend_helpers.dart' show BackendHelpers;
 import '../js_backend/js_backend.dart';
 import '../native/native.dart' as native;
-import '../tree/tree.dart' as ast;
+import '../tree/dartstring.dart' as ast;
 import '../types/types.dart';
 import '../universe/selector.dart' show Selector;
 import '../universe/side_effects.dart' show SideEffects;

pkg/compiler/lib/src/string_validator.dart

@@ -10,7 +10,8 @@ import 'dart:collection';
 
 import 'common.dart';
 import 'tokens/token.dart' show Token;
-import 'tree/tree.dart';
+import 'tree/nodes.dart' show StringQuoting;
+import 'tree/dartstring.dart' show DartString;
 import 'util/characters.dart';
 
 class StringValidator {