Fixed a bug in the ASTImporter that affects

types that have been imported multiple times.

The discussion below uses this diagram:

ASTContext     A      B      C
Decl           Da     Db     Dc
ASTImporter    \-Iab-/\-Iac-/
               \-----Iac----/

When a Decl D is imported from ASTContext A to
ASTContext B, the ASTImporter Iab records the
pair <Da, Db> in a DenseMap.  That way, if Iab
ever encounters Da again (for example, as the
DeclContext for another Decl), it can use the
imported version.  This is not an optimization,
it is critical: if I import the field "st_dev"
as part of importing "struct stat," the field
must have DeclContext equal to the parent
structure or we end up with multiple different
Decls containing different parts of "struct
stat."  "struct stat" is imported once and
recorded in the DenseMap; then the ASTImporter
finds that same version when looking for the
DeclContext of "st_dev."

The bug arises when Db is imported into another
ASTContext C and ASTContext B goes away.  This
often occurs when LLDB produces result variables
for expressions.  Ibc is aware of the transport
of Db to Dc, but a brand new ASTImporter, Iac,
is responsible for completing Dc from its source
upon request.  That ASTImporter has no mappings,
so it will produce a clone of Dc when attempting
to import its children.  That means that type
completion operations on Dc will fail.

The solution is to create Iac as soon as Ibc
imports D from B to C, and inform Iac of the
mapping between Da and Dc.  This allows type
completion to happen correctly.

llvm-svn: 147016

lldb/source/Symbol/ClangASTImporter.cpp

@@ -356,6 +356,11 @@ clang::Decl
         {
             to_context_md->m_origins[to] = origin_iter->second;
             
+            MinionSP direct_completer = m_master.GetMinion(&to->getASTContext(), origin_iter->second.ctx);
+            
+            if (direct_completer.get() != this)
+                direct_completer->ASTImporter::Imported(origin_iter->second.decl, to);
+            
             if (log)
                 log->Printf("    [ClangASTImporter] Propagated origin (Decl*)%p/(ASTContext*)%p from (ASTContext*)%p to (ASTContext*)%p",
                             origin_iter->second.decl,