[clang] [Clang][Sema] Refactor collection of multi-level template argument lists (PR #106585)

[Krystian Stasiowski via cfe-commits]

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@@ -33,11 +33,12 @@ class D{}; // expected-note{{previous definition is here}}
 template<typename T>
 class D<T>{}; // expected-error{{class template partial specialization does not specialize any template argument; to define the primary template, remove the template argument list}} expected-error{{redefinition of 'D'}}
 
-template<typename T> requires C1<T> // expected-note{{previous template declaration is here}}
-class E{};
+template<typename T> requires C1<T>
+class E{}; // expected-note{{previous definition is here}}
 
-template<typename T> // expected-error{{requires clause differs in template redeclaration}}
+template<typename T>
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sdkrystian wrote:

I can move the point at which we emit the redefinition error to be after the check for equivalent _template-heads_, if you'd like. Then we would get the "requires clause differs in template redeclaration" error instead.

https://github.com/llvm/llvm-project/pull/106585