[clang] [clang] Expand invalid PCM diagnostic (PR #69489)

[Nuri Amari via cfe-commits]

https://github.com/NuriAmari created https://github.com/llvm/llvm-project/pull/69489

Summary:

When a PCM file is loaded, it can go wrong in various ways. The current diagnostic only produces the name of the malformed PCM, not why it is malformed. Expand the diagnostic to display what went wrong!

There is only one call site for this diagnostic, and it already passes the error message:

https://github.com/llvm/llvm-project/blob/main/clang/lib/Serialization/ASTReader.cpp#L4763-L4764

Test Plan:

The modified LIT test.

>From 3fa795fae47d00ece00e9414a268610d3c4a6bf3 Mon Sep 17 00:00:00 2001
From: Nuri Amari <nuriamari at meta.com>
Date: Fri, 22 Sep 2023 12:03:23 -0700
Subject: [PATCH] Expand invalid PCM diagnostic

Summary:

When a PCM file is loaded, it can go wrong in various ways. The current
diagnostic only produces the name of the malformed PCM, not why
it is malformed. Expand the diagnostic to display what went wrong!

There is only one call site for this diagnostic, and it
already passes the error message.

Test Plan:

The modified LIT test.
---
 clang/include/clang/Basic/DiagnosticSerializationKinds.td | 2 +-
 clang/test/Modules/explicit-build.cpp                     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSerializationKinds.td b/clang/include/clang/Basic/DiagnosticSerializationKinds.td
index a1ae23a62802104..1c049792d16eda4 100644
--- a/clang/include/clang/Basic/DiagnosticSerializationKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSerializationKinds.td
@@ -62,7 +62,7 @@ def err_ast_file_out_of_date : Error<
   "%select{PCH|module|AST}0 file '%1' is out of date and "
   "needs to be rebuilt%select{|: %3}2">, DefaultFatal;
 def err_ast_file_invalid : Error<
-  "file '%1' is not a valid precompiled %select{PCH|module|AST}0 file">, DefaultFatal;
+  "file '%1' is not a valid precompiled %select{PCH|module|AST}0 file: '%2'">, DefaultFatal;
 def note_module_file_imported_by : Note<
   "imported by %select{|module '%2' in }1'%0'">;
 def err_module_file_not_module : Error<
diff --git a/clang/test/Modules/explicit-build.cpp b/clang/test/Modules/explicit-build.cpp
index 16eb604708c9d83..42444369dc92c5f 100644
--- a/clang/test/Modules/explicit-build.cpp
+++ b/clang/test/Modules/explicit-build.cpp
@@ -161,7 +161,7 @@
 // RUN:            -fmodule-file=%t/not.pcm \
 // RUN:            %s 2>&1 | FileCheck --check-prefix=CHECK-BAD-FILE %s
 //
-// CHECK-BAD-FILE: fatal error: file '{{.*}}not.pcm' is not a valid precompiled module file
+// CHECK-BAD-FILE: fatal error: file '{{.*}}not.pcm' is not a valid precompiled module file: 'file too small to contain AST file magic'
 
 // RUN: not %clang_cc1 -x c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -Rmodule-build -fno-modules-error-recovery \
 // RUN:            -fmodule-file=%t/nonexistent.pcm \