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

[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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apple-fcloutier wrote:

Not that I'm aware of. Before this change, <scratch space> buffers are used only for macro expansion. (The other specially-named buffers are `<built-in>` and `<command line>`, but we really could call it anything.) As far as I know, diagnosing based on the string result of compile-time evaluation is unprecedented and we need to do _something_ new one way or another.

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