[clang] [Clang] [Sema] Fix a crash when a `friend` function is redefined as deleted (PR #135679)

[Shafik Yaghmour via cfe-commits]

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@@ -271,3 +271,33 @@ void operators() {
   if (to_int_int) {} // expected-error {{attempt to use a deleted function: deleted (TO<int, int>, operator bool)}}
   static_cast<bool>(to_int_int); // expected-error {{static_cast from 'TO<int, int>' to 'bool' uses deleted function: deleted (TO<int, int>, operator bool)}}
 };
+
+namespace gh135506 {
+struct a {
+  // FIXME: We currently don't diagnose these invalid redeclarations if the
+  // second declaration is defaulted or deleted. This probably needs to be
+  // handled in ParseCXXInlineMethodDef() after parsing the defaulted/deleted
+  // body.
+  friend consteval int f() { return 3; }
+  friend consteval int f() = delete("foo");
+
+  friend consteval int g() { return 3; }
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shafik wrote:

We should also test `constexpr` as well.

https://github.com/llvm/llvm-project/pull/135679