[Modules] Don't infinite recurse on implicit import of circular modules in preamble

Update the Preprocessor's VisibleModuleSet when typo-correction creates
an implicit module import so that we won't accidentally write an invalid
SourceLocation into the preamble AST.  This would later lead to infinite
recursion when loading the preamble AST because we use the value in
ImportLocs to prevent visiting a module twice.

rdar://problem/24440990

llvm-svn: 260543

1 files changed, 1 insertions, 0 deletions

diff --git a/clang/lib/Basic/Module.cpp b/clang/lib/Basic/Module.cpp
index baeeb9edbdd..e119c0535eb 100644
--- a/clang/lib/Basic/Module.cpp
+++ b/clang/lib/Basic/Module.cpp
@@ -492,6 +492,7 @@ LLVM_DUMP_METHOD void Module::dump() const {
 
 void VisibleModuleSet::setVisible(Module *M, SourceLocation Loc,
                                   VisibleCallback Vis, ConflictCallback Cb) {
+  assert(Loc.isValid() && "setVisible expects a valid import location");
   if (isVisible(M))
     return;