[clang] [clang] mangle placeholder for deduced type as a template-prefix (PR #106335)

[via cfe-commits]

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@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -std=c++20 %s -triple %itanium_abi_triple -emit-llvm -o - | FileCheck %s
+
+template <template <class> class S>
+void create_unique()
+  requires (S{0}, true) {}
+
+template <class Fn> struct A {
+  constexpr A(Fn) {};
+};
+
+template void create_unique<A>();
+// CHECK: @_Z13create_uniqueI1AEvvQcmtlT_Li0EELb1E(
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h-vetinari wrote:

> @AaronBallman: I think we've missed the 19.x cycle for this because it involves an ABI break (and final goes out in less than a week [...]

The process does have some leeway for further RCs though if there are many (or critical) regressions, c.f. statement from @tru [here](https://discourse.llvm.org/t/llvm-19-release-schedule-and-planning/79828):
> We have previously inserted a 4th RC when there were a lot of outstanding bugs.



https://github.com/llvm/llvm-project/pull/106335