[dart2dart] Cut declaration types by default if we check that it is safe to do so.

lib/compiler/implementation/dart_backend/backend.dart

Index: lib/compiler/implementation/dart_backend/backend.dart
diff --git a/lib/compiler/implementation/dart_backend/backend.dart b/lib/compiler/implementation/dart_backend/backend.dart
index f8436915f549084f126612d43627f88d6f351c85..842d0302b6466bb3f6d0cb0dd4c009e503417c82 100644
--- a/lib/compiler/implementation/dart_backend/backend.dart
+++ b/lib/compiler/implementation/dart_backend/backend.dart
@@ -89,6 +89,67 @@ class DartBackend extends Backend {
   Map<Element, TreeElements> get resolvedElements =>
       compiler.enqueuer.resolution.resolvedElements;
 
+  /**
+   * Tells whether it is safe to remove type declarations from variables, functions

[Anton Muhin, 2012/09/17 18:45:15]

nit: isn't this string too long?

[Roman, 2012/09/18 10:24:08]

Sorry, forgot to check long lines before sending to review. Fixed everywhere.

+   * parameters. It becomes not safe if:
+   * 1) TypeError is used somewhere in the code,
+   * 2) The code has typedefs in right hand side of IS checks,
+   * 3) The code has classes which extend typedefs, have type arguments typedefs
+   *    or type variable bounds typedefs.
+   * These restrictions can be less strict.
+   */
+  bool isSafeToRemoveTypeDeclarations(Map<ClassElement, Set<Element>> classMembers) {

[Anton Muhin, 2012/09/17 18:45:15]

generic question: why do you have to parse elements?  isn't information in
DartTypes enough for you?

[Roman, 2012/09/18 10:24:08]

Unfortunately, no. When I have:
class A extends B<C> {}

then type A supertype refers to generic B<T> instead of concrete B<C>.

+    Set<DartType> processedTypes = new Set<DartType>();
+    List<DartType> workQueue = new List<DartType>();
+    workQueue.addAll(classMembers.getKeys().map((classElement) => classElement.type));

[Anton Muhin, 2012/09/17 18:45:15]

ditto for this line and all the lines below

+    workQueue.addAll(compiler.resolverWorld.isChecks);
+    DartType typeErrorType = compiler.coreLibrary.find(new SourceString('TypeError')).type;
+    if (workQueue.indexOf(typeErrorType) != -1) {
+      return true;
+    }
+
+    void processTypeArguments(Element classElement, NodeList typeArguments) {
+      if (typeArguments == null) return;
+      for (Node typeArgument in typeArguments.nodes.toList()) {

[Anton Muhin, 2012/09/17 18:45:15]

do you need .toList()?

[Roman, 2012/09/18 10:24:08]

Indeed I don't, Link is iterable. Removed.

+        if (typeArgument is TypeVariable) {
+          typeArgument = typeArgument.bound;
+        }
+        if (typeArgument == null) continue;
+        assert(typeArgument is TypeAnnotation);
+        DartType argumentType = compiler.resolveTypeAnnotation(classElement, typeArgument);
+        assert(argumentType !== null);
+        workQueue.add(argumentType);

[Anton Muhin, 2012/09/17 18:45:15]

shouldn't you check processedTypes before adding anything into the queue?

[Roman, 2012/09/18 10:24:08]

Not necessary, when I pop next work element, I check if it was processed.

[Anton Muhin, 2012/09/18 10:27:03]

Yes, I know, we can just consume less memory.  Overall, you may want to revisit
your approach and bailout earlier on addition of 'bad' type.

On 2012/09/18 10:24:08, Roman wrote:

[Roman, 2012/09/18 13:12:21]

It is possible that we can add processed items several times, but right now it's
not clear that we're wasting much memory or are experiencing significant
slowdown because of this.

+      }
+    }
+
+    while (!workQueue.isEmpty()) {
+      DartType type = workQueue.removeLast();
+      if (processedTypes.contains(type)) continue;
+      processedTypes.add(type);
+      if (type is TypedefType) return true;
+      if (type is InterfaceType) {
+        ClassElement element = type.element;
+        ClassNode node = element.parseNode(compiler);
+        // Check class type args.
+        processTypeArguments(element, node.typeParameters);
+        // Check superclass type args.
+        if (node.superclass !== null) {
+          NodeList typeArguments = node.superclass.typeArguments;
+          processTypeArguments(element, node.superclass.typeArguments);
+        }
+        // Check interfaces type args.
+        for (Node interfaceNode in node.interfaces) {
+          processTypeArguments(element, (interfaceNode as TypeAnnotation).typeArguments);
+        }
+        // Check all supertypes.
+        if (element.allSupertypes !== null) {
+          workQueue.addAll(element.allSupertypes.toList());
+        }
+      }
+    }
+    return false;
+  }
+
   DartBackend(Compiler compiler, this.cutDeclarationTypes)
       : tasks = <CompilerTask>[],
         super(compiler);
@@ -233,13 +294,14 @@ class DartBackend extends Backend {
       }
     }
     topLevelElements.forEach(makePlaceholders);
-
     // Create renames.
     Map<Node, String> renames = new Map<Node, String>();
     Map<LibraryElement, String> imports = new Map<LibraryElement, String>();
+    bool shouldCutDeclarationTypes =
+        cutDeclarationTypes || !isSafeToRemoveTypeDeclarations(classMembers);
     renamePlaceholders(
         compiler, collector, renames, imports,
-        fixedMemberNames, cutDeclarationTypes);
+        fixedMemberNames, shouldCutDeclarationTypes));
 
     // Sort elements.
     final sortedTopLevels = sortElements(topLevelElements);
@@ -288,6 +350,21 @@ class DartBackend extends Backend {
   log(String message) => compiler.log('[DartBackend] $message');
 }
 
+/*

[Anton Muhin, 2012/09/17 18:45:15]

commented out code

[Roman, 2012/09/18 10:24:08]

That was my first emotional attempt to write another visitor./ Removed.

+class TypedefRhsChecker extends AbstractVisitor {
+  static bool hasTypedefsRhs(Node node) {
+    TypedefRhsChecker checker = new TypedefRhsChecker();
+    node.accept(checker);
+  }
+
+  visitNode(Node node) { node.visitChildren(this); }
+
+  visitSend(Send node) {
+    if (node.isOperator && node.op)
+  }
+}
+*/
+
 /**
  * Some elements are not recorded by resolver now,
  * for example, typedefs or classes which are only