[clang] [Clang] Fix handling of pack indexing types in constraints of redeclaration (PR #139057)

[via cfe-commits]

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@@ -779,3 +781,59 @@ template <typename T>
 consteval void S::mfn() requires (bool(&fn)) {}
 
 }
+
+
+namespace GH138255 {
+
+  template <typename... T>
+  concept C = true;
+
+  struct Func {
+      template<typename... Ts>
+      requires C<Ts...[0]>
+      static auto buggy() -> void;
+
+      template<typename... Ts>
+      requires C<Ts...[0]>
+      friend auto fr() -> void;
+
+      template<typename... Ts>
+      requires C<Ts...[0]>
+      friend auto fr2() -> void{}; // expected-note{{previous definition is here}}
+  };
+
+  template<typename... Ts>
+  requires C<Ts...[0]>
+  auto Func::buggy() -> void {}
+
+  template<typename... Ts>
+  requires C<Ts...[0]>
+  auto fr() -> void {}
+
+  template<typename... Ts>
+  requires C<Ts...[0]>
+  auto fr2() -> void {} // expected-error{{redefinition of 'fr2'}}
+
+
+  template <typename... Ts>
+  requires C<Ts...[0]>
+  struct Class;
+
+  template <typename... Ts>
+  requires C<Ts...[0]>
+  struct Class;
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cor3ntin wrote:

I'm checking that redeclaring does not cause a diagnostic

https://github.com/llvm/llvm-project/pull/139057