Issue 6073. Fixes for 'export'.

compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java

Index: compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java b/compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
index 2a4e52b933eb38a420af520becab31c69e16f81f..3cb47c748f863b5073eba05d4464818746c6c814 100644
--- a/compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
+++ b/compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
@@ -7,6 +7,7 @@ package com.google.dart.compiler.resolver;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
 import com.google.dart.compiler.DartCompilationError;
 import com.google.dart.compiler.DartCompilerContext;
 import com.google.dart.compiler.DartCompilerListener;
@@ -35,6 +36,7 @@ import com.google.dart.compiler.util.apache.StringUtils;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 /**
  * Builds all class elements and types of a library. Once all libraries
@@ -63,18 +65,25 @@ public class TopLevelElementBuilder {
    * libraries.
    */
   public void fillInLibraryScope(LibraryUnit library, DartCompilerListener listener) {
+    fillInLibraryScope(library, listener, Sets.newHashSet());
+  }
+    
+    /**
+     * Fill the scope for this library, using its own top-level elements and elements from imported
+     * libraries.
+     */
+  private void fillInLibraryScope(LibraryUnit library, DartCompilerListener listener,
+      Set<Object> processedObjects) {
     Scope importScope = library.getElement().getImportScope();
     Scope scope = library.getElement().getScope();
     
-    // We are processing this library now, or already done this. 
-    if (library.getElement().getScope().isStateProgress()
-        || library.getElement().getScope().isStateReady()) {
+    // We are done with this library. 
+    if (library.getElement().getScope().isStateReady()) {
       return;
     }
-    library.getElement().getScope().markStateProgress();
 
     // Fill "library" scope.
-    {
+    if (processedObjects.add(library)) {

[Brian Wilkerson, 2012/10/20 17:39:43]

I don't understand this. If we've already processed this library, shouldn't we
return without doing any further work? But it looks like we'll skip past the
'if' block to process the imports and exports a second time. It probably won't
hurt anything because we're also adding the imports and exports to the set of
processed objects, but it seems inefficient.

[scheglov, 2012/10/20 18:21:27]

We need this for the case when library A imports B and B imports A, and B
reexports something from C, which is used by A. In this case we process A until
we find import of B, then dive into processing B, process it until import of A,
dive again into processing A but skip all imports which were already process in
A before.

[Brian Wilkerson, 2012/10/20 19:05:18]

Ah! The joys of mutually recursive libraries! Thanks, I understand now.

       List<Element> exportedElements = Lists.newArrayList();
       {
         DartUnit selfUnit = library.getSelfDartUnit();
@@ -100,8 +109,12 @@ public class TopLevelElementBuilder {
       }
     }
 
+    // Fill "import" scope.
     Map<String, LibraryPrefixElement> libraryPrefixElements = Maps.newHashMap();
     for (LibraryImport libraryImport : library.getImports()) {
+      if (!processedObjects.add(libraryImport)) {
+        continue;
+      }
       LibraryUnit lib = libraryImport.getLibrary();
       // Prepare scope for this import.
       Scope scopeForImport;
@@ -128,7 +141,7 @@ public class TopLevelElementBuilder {
         }
       }
       // Prepare "lib" scope.
-      fillInLibraryScope(lib, listener);
+      fillInLibraryScope(lib, listener, processedObjects);
       // Fill "library" scope with element exported from "lib".
       for (Element element : lib.getElement().getExportedElements()) {
         String name = element.getName();
@@ -141,10 +154,14 @@ public class TopLevelElementBuilder {
         }
       }
     }
+
     // Fill "library" export scope with re-exports.
     for (LibraryExport export : library.getExports()) {
+      if (!processedObjects.add(export)) {
+        continue;
+      }
       LibraryUnit lib = export.getLibrary();
-      fillInLibraryScope(lib, listener);
+      fillInLibraryScope(lib, listener, processedObjects);
       for (Element element : lib.getElement().getExportedElements()) {
         String name = element.getName();
         // re-export only in not defined locally
@@ -157,6 +174,7 @@ public class TopLevelElementBuilder {
         }
       }
     }
+
     // Done.
     library.getElement().getScope().markStateReady();
   }