https://github.com/Li-Zheng-Rong created 
https://github.com/llvm/llvm-project/pull/199343

When checking for multiple source files declaring the same module, the 
comparison used raw string equality on file paths. This causes false positives 
when the same file is represented by different but equivalent path strings.

Use pathEqual(normalizePath(...), normalizePath(...)) instead to compare 
canonical paths, consistent with how clangd handles path comparisons elsewhere.

>From 6fe84eb5fecab14ca5ed411caa43d7a80527706e Mon Sep 17 00:00:00 2001
From: Li-Zheng-Rong <[email protected]>
Date: Sat, 23 May 2026 18:47:44 +0800
Subject: [PATCH] [NFC] [clangd] [C++20] [Modules] Fix false duplicate module
 warning for equivalent paths

When checking for multiple source files declaring the same module,
the comparison used raw string equality on file paths. This causes
false positives when the same file is represented by different but
equivalent path strings.

Use pathEqual(normalizePath(...), normalizePath(...)) instead to
compare canonical paths, consistent with how clangd handles path
comparisons elsewhere.
---
 clang-tools-extra/clangd/ProjectModules.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clangd/ProjectModules.cpp 
b/clang-tools-extra/clangd/ProjectModules.cpp
index d3727171bff12..33cbc715e9659 100644
--- a/clang-tools-extra/clangd/ProjectModules.cpp
+++ b/clang-tools-extra/clangd/ProjectModules.cpp
@@ -247,7 +247,8 @@ ModuleDependencyScanner::scan(PathRef FilePath,
     auto [Iter, Inserted] = ModuleNameToSource.try_emplace(
         ScanningResult->Provides->ModuleName, FilePath);
 
-    if (!Inserted && Iter->second != FilePath) {
+    if (!Inserted &&
+        !pathEqual(normalizePath(Iter->second), normalizePath(FilePath))) {
       elog("Detected multiple source files ({0}, {1}) declaring the same "
            "module: '{2}'. "
            "Now clangd may find the wrong source in such case.",

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