[clang-tools-extra] [clang-tidy] Fix spurious errors from builtin macros in modernize-use-trailing-return-type (PR #184022)

[via cfe-commits]

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@@ -487,6 +487,15 @@ decltype(COMMAND_LINE_INT{}) h21();
 // CHECK-MESSAGES: :[[@LINE-1]]:30: warning: use a trailing return type for this function [modernize-use-trailing-return-type]
 // CHECK-FIXES: auto h21() -> decltype(COMMAND_LINE_INT{});
 
+// Builtin macros like __has_feature are registered as object-like macros but
+// require function-like syntax when expanded. Ensure the check does not cause
+// spurious "missing '(' after '__has_feature'" errors when they appear in the
+// raw lex span of a function return type.
+const decltype(__has_feature(cxx_constexpr)) h22();
+// CHECK-MESSAGES: :[[@LINE-1]]:46: warning: use a trailing return type for this function [modernize-use-trailing-return-type]
+const decltype(__has_builtin(__builtin_expect)) h23();
+// CHECK-MESSAGES: :[[@LINE-1]]:49: warning: use a trailing return type for this function [modernize-use-trailing-return-type]
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vadikmironov wrote:

Done, check() emits the warning, but no fixit and hence checking for the unchanged function.

https://github.com/llvm/llvm-project/pull/184022