[clang] [clang][Sema] fix Crash when lookup finds UnresolvedUsingValueDecl followed by '<' (PR #190322)

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+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// expected-no-diagnostics
+
+// This is a regression test that verifies handling a mix of using-declarations
+// from dependent and non-dependent base classes does not cause name lookup
+// to crash when a dependent entity cannot be converted to a TemplateDecl.
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firstmoonlight wrote:

Thanks, I have add namespace `GH174951`

https://github.com/llvm/llvm-project/pull/190322