[clang] [Clang][Parse] Diagnose requires expressions with explicit object parameters (PR #88974)

[Krystian Stasiowski via cfe-commits]

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@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify %s
+
+auto x0 = requires (this int) { true; }; // expected-error {{a requires clause cannot have an explicit object parameter}}
+auto x1 = requires (int, this int) { true; }; // expected-error {{a requires clause cannot have an explicit object parameter}}
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sdkrystian wrote:

@cor3ntin sure, but non-type template parameter parsing doesn't use `ParseParameterDeclarationClause` -- it is done in [`ParseNonTypeTemplateParameter`](https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseTemplate.cpp#L895)

https://github.com/llvm/llvm-project/pull/88974