[clang] [Clang] prevent recovery call expression from proceeding with explicit attributes and undeclared templates (PR #107786)

[Erich Keane via cfe-commits]

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@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+
+namespace GH49093 {
+  class B {
+  public:
+    static int a() { return 0; } // expected-note {{member is declared here}}
+    decltype(a< 0 >(0)) test;    // expected-error {{member 'a' used before its declaration}}
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erichkeane wrote:

I think it generally DOES make sense to try the lookup?  We shouldn't crash of course, but failing to do the lookup pretending it is NOT a template makes a lot of sense to me.  

https://github.com/llvm/llvm-project/pull/107786