1 files changed, 20 insertions, 0 deletions
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index f57246bec09..4199cbe0f66 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1188,6 +1188,19 @@ compileModuleImpl(CompilerInstance &ImportingInstance, SourceLocation ImportLoc,
   return !Instance.getDiagnostics().hasErrorOccurred();
 }
 
+static const FileEntry *getPublicModuleMap(const FileEntry *File,
+                                           FileManager &FileMgr) {
+  StringRef Filename = llvm::sys::path::filename(File->getName());
+  SmallString<128> PublicFilename(File->getDir()->getName());
+  if (Filename == "module_private.map")
+    llvm::sys::path::append(PublicFilename, "module.map");
+  else if (Filename == "module.private.modulemap")
+    llvm::sys::path::append(PublicFilename, "module.modulemap");
+  else
+    return nullptr;
+  return FileMgr.getFile(PublicFilename);
+}
+
 /// \brief Compile a module file for the given module, using the options 
 /// provided by the importing compiler instance. Returns true if the module
 /// was built without errors.
@@ -1204,6 +1217,13 @@ static bool compileModuleImpl(CompilerInstance &ImportingInstance,
   bool Result;
   if (const FileEntry *ModuleMapFile =
           ModMap.getContainingModuleMapFile(Module)) {
+    // Canonicalize compilation to start with the public module map. This is
+    // vital for submodules declarations in the private module maps to be
+    // correctly parsed when depending on a top level module in the public one.
+    if (const FileEntry *PublicMMFile = getPublicModuleMap(
+            ModuleMapFile, ImportingInstance.getFileManager()))
+      ModuleMapFile = PublicMMFile;
+
     // Use the module map where this module resides.
     Result = compileModuleImpl(
         ImportingInstance, ImportLoc, Module->getTopLevelModuleName(),