[clang] [Clang] Added nullptr check to getFriendDecl access (PR #121056)

[via cfe-commits]

================
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+// Ensure the following out of line friend declaration doesn't cause the compiler to crash.
+
+class A {
+  friend bool operator==(const A&, const A&);
+  friend class B;
+};
+
+bool operator==(const A&, const A&) = default;
+
----------------
cor3ntin wrote:

I found a couple additional tests that are interesting (the second of which happens to crash gcc) https://compiler-explorer.com/z/eb6PeP6ar

https://github.com/llvm/llvm-project/pull/121056