[Modules] Improve ReadASTBlock error message when module not available
Point to the PCM file that could not be found.
rdar://problem/30381981
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index c5edca7..9d50f7a 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -2976,7 +2976,10 @@
Data += Len;
ModuleFile *OM = ModuleMgr.lookup(Name);
if (!OM) {
- Error("SourceLocation remap refers to unknown module");
+ std::string Msg =
+ "SourceLocation remap refers to unknown module, cannot find ";
+ Msg.append(Name);
+ Error(Msg);
return Failure;
}