When making modules transitively visible, don't take into account
whether they have missing header files.
Whether a module's headers happen to be present on the local file system
should make no difference to whether we make its contents visible when
importing another module that re-exports it. If we have an up-to-date
AST file that we can load, that's all that matters.
This fixes the ability to header syntax checking for modular headers in
C++20 mode (or in prior modes where -fmodules-local-submodule-visibility
is enabled but -fmodules is not).
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 18a92aa..31d004f 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1729,7 +1729,8 @@
llvm::SmallVector<Module *, 16> Worklist(1, WritingModule);
while (!Worklist.empty()) {
Module *M = Worklist.pop_back_val();
- if (!M->isAvailable())
+ // We don't care about headers in unimportable submodules.
+ if (M->isUnimportable())
continue;
// Map to disk files where possible, to pick up any missing stat