[clang] [Clang][Preprocessor] Unify header-name lookahead for import and include (PR #191004)

[Hubert Tong via cfe-commits]

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@@ -422,6 +422,7 @@ Bug Fixes in This Version
 - Fixed a crash on _BitInt(N) arrays where 129 ≤ N ≤ 192 due to incorrect array filler lowering. (#GH189643)
 - Fixed the behavior in C23 of ``auto``, by emitting an error when an array type is specified for a ``char *``. (#GH162694)
 - Fixed incorrect rejection of ``auto`` with reordered declaration specifiers in C23. (#GH164121)
+- Fixed incorrect handling of header-name lookahead in C++ import and #include directives involving digraphs and macro expansion. (#GH190693)
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hubert-reinterpretcast wrote:

> Can we drop support for this path format in a future version of Clang?

I would imagine that this path format is not "actively" supported by Clang but rather supported as a consequence of the filesystem APIs on the host system (i.e., there's nothing to "drop" per se).

https://github.com/llvm/llvm-project/pull/191004