Revert "[Modules] Don't fail when an unused textual header is missing. (#138227)"

This reverts commit 64bb60a471a5ddc9c9bec413c65fdab730a1e4b0.

Revert to give more time affected parties to adjust to the change.

1 files changed, 2 insertions, 4 deletions

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 4175959..e899e0c 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -310,10 +310,8 @@ void ModuleMap::resolveHeader(Module *Mod,
   } else if (Header.HasBuiltinHeader && !Header.Size && !Header.ModTime) {
     // There's a builtin header but no corresponding on-disk header. Assume
     // this was supposed to modularize the builtin header alone.
-  } else if ((Header.Kind == Module::HK_Excluded) ||
-             (Header.Kind == Module::HK_Textual)) {
-    // Ignore excluded and textual header files as a module can be built with
-    // such headers missing.
+  } else if (Header.Kind == Module::HK_Excluded) {
+    // Ignore missing excluded header files. They're optional anyway.
   } else {
     // If we find a module that has a missing header, we mark this module as
     // unavailable and store the header directive for displaying diagnostics.