clang/Modules: Add missing diagnostics for malformed AST files

These were found via an audit.  In the case of `ParseLineTable` this is
actually dead code, since parsing the line table always succeeds, but
it's prudent to be defensive since it's possible an assertion there
could be converted to a `true` return in the future.

1 files changed, 6 insertions, 2 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index a5cd9e9f83e..b780335233b 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -3408,8 +3408,10 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       break;
 
     case SOURCE_MANAGER_LINE_TABLE:
-      if (ParseLineTable(F, Record))
+      if (ParseLineTable(F, Record)) {
+        Error("malformed SOURCE_MANAGER_LINE_TABLE in AST file");
         return Failure;
+      }
       break;
 
     case SOURCE_LOCATION_PRELOADS: {
@@ -4771,8 +4773,10 @@ ASTReader::ASTReadResult ASTReader::ReadExtensionBlock(ModuleFile &F) {
     switch (MaybeRecCode.get()) {
     case EXTENSION_METADATA: {
       ModuleFileExtensionMetadata Metadata;
-      if (parseModuleFileExtensionMetadata(Record, Blob, Metadata))
+      if (parseModuleFileExtensionMetadata(Record, Blob, Metadata)) {
+        Error("malformed EXTENSION_METADATA in AST file");
         return Failure;
+      }
 
       // Find a module file extension with this block name.
       auto Known = ModuleFileExtensions.find(Metadata.BlockName);