prevent cached DartUnit from being referenced and resolved by multiple libraries

compiler/java/com/google/dart/compiler/DartCompiler.java

Index: compiler/java/com/google/dart/compiler/DartCompiler.java
===================================================================
--- compiler/java/com/google/dart/compiler/DartCompiler.java	(revision 6466)
+++ compiler/java/com/google/dart/compiler/DartCompiler.java	(working copy)
@@ -881,7 +881,9 @@
         return super.parse(dartSrc, prefixes, diet);
       }
       URI srcUri = dartSrc.getUri();
-      DartUnit parsedUnit = parsedUnits.get(srcUri);
+      // Remove the parsed unit from the map if present
+      // so that it will not be consumed a 2nd time if it is sourced by multiple libraries
+      DartUnit parsedUnit = parsedUnits.remove(srcUri);

[zundel, 2012/04/12 19:00:34]

couldn't you just not parse it a second time?  Or does this parsedUnits persist
between runs of the analyzer?

[danrubel, 2012/04/12 19:17:44]

If I analyze a library that imports two other libraries, each of which #source
the same file, and that file is in the parsedUnits cache, then that same
DartUnit ends up being referenced by two different libraries, and the resolver
breaks when it tries to resolve that DartUnit a 2nd time. This was the easiest
solution... remove the DartUnit from the cache once it is attached to a library.

       return parsedUnit == null ? super.parse(dartSrc, prefixes, diet) : parsedUnit;
     }
   }
@@ -1157,7 +1159,8 @@
    * instead of parsing and resolving the associated source from storage.
    * @param parsedUnits A collection of unresolved ASTs that should be used
    * instead of parsing the associated source from storage. Intended for
-   * IDE use when modified buffers must be analyzed. AST nodes in the map may be
+   * IDE use when modified buffers must be analyzed. 
+   * Units are removed from this map as they are used. AST nodes in the map may be
    * ignored if not referenced by {@code lib}. (May be null.)
    * @param config The compiler configuration (phases and backends
    * will not be used), but resolution and type-analysis will be