[clang] [clang] Constant-evaluate format strings as last resort (PR #135864)

[Aaron Ballman via cfe-commits]

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@@ -3,6 +3,11 @@
 // RUN: %clang_cc1 -fblocks -fsyntax-only -verify -Wformat-nonliteral -isystem %S/Inputs -triple=x86_64-unknown-fuchsia %s
 // RUN: %clang_cc1 -fblocks -fsyntax-only -verify -Wformat-nonliteral -isystem %S/Inputs -triple=x86_64-linux-android %s
 
+// expected-note at -5{{format string was constant-evaluated}}
+// ^^^ there will be a <scratch space> SourceLocation caused by the
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AaronBallman wrote:

I'm not too worried about performance, but I can see where the concerns come from. It may be worth it to put a branch up on https://llvm-compile-time-tracker.com/ to verify we're not slowing things down too much, but I also don't think it's strictly required. (Checking diagnostic IDs to see if the check is disabled would be really awkward and I think we should avoid it in this case.)

https://github.com/llvm/llvm-project/pull/135864