[ASTImporter] Add importer specific lookup

Summary:
There are certain cases when normal C/C++ lookup (localUncachedLookup)
does not find AST nodes. E.g.:

Example 1:

  template <class T>
  struct X {
    friend void foo(); // this is never found in the DC of the TU.
  };

Example 2:

  // The fwd decl to Foo is not found in the lookupPtr of the DC of the
  // translation unit decl.
  struct A { struct Foo *p; };

In these cases we create a new node instead of returning with the old one.
To fix it we create a new lookup table which holds every node and we are
not interested in any C++ specific visibility considerations.
Simply, we must know if there is an existing Decl in a given DC.

Reviewers: a_sidorin, a.sidorin

Subscribers: mgorny, rnkovacs, dkrupp, Szelethus, cfe-commits

Differential Revision: https://reviews.llvm.org/D53708

llvm-svn: 349351

1 files changed, 6 insertions, 5 deletions

diff --git a/clang/lib/Frontend/ASTMerge.cpp b/clang/lib/Frontend/ASTMerge.cpp
index 2434113ab0d..4f622da118c 100644
--- a/clang/lib/Frontend/ASTMerge.cpp
+++ b/clang/lib/Frontend/ASTMerge.cpp
@@ -10,6 +10,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/ASTImporter.h"
+#include "clang/AST/ASTImporterLookupTable.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendActions.h"
@@ -38,6 +39,8 @@ void ASTMergeAction::ExecuteAction() {
                                        &CI.getASTContext());
   IntrusiveRefCntPtr<DiagnosticIDs>
       DiagIDs(CI.getDiagnostics().getDiagnosticIDs());
+  ASTImporterLookupTable LookupTable(
+      *CI.getASTContext().getTranslationUnitDecl());
   for (unsigned I = 0, N = ASTFiles.size(); I != N; ++I) {
     IntrusiveRefCntPtr<DiagnosticsEngine>
         Diags(new DiagnosticsEngine(DiagIDs, &CI.getDiagnosticOpts(),
@@ -51,11 +54,9 @@ void ASTMergeAction::ExecuteAction() {
     if (!Unit)
       continue;
 
-    ASTImporter Importer(CI.getASTContext(),
-                         CI.getFileManager(),
-                         Unit->getASTContext(),
-                         Unit->getFileManager(),
-                         /*MinimalImport=*/false);
+    ASTImporter Importer(CI.getASTContext(), CI.getFileManager(),
+                         Unit->getASTContext(), Unit->getFileManager(),
+                         /*MinimalImport=*/false, &LookupTable);
 
     TranslationUnitDecl *TU = Unit->getASTContext().getTranslationUnitDecl();
     for (auto *D : TU->decls()) {