[clang] [Clang] Fix ICE in constraint normalization when substituting concept template parameters (PR #184406)

[Younan Zhang via cfe-commits]

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@@ -4481,11 +4481,39 @@ ExprResult Sema::SubstConceptTemplateArguments(
 
     ExprResult TransformUnresolvedLookupExpr(UnresolvedLookupExpr *E,
                                              bool IsAddressOfOperand = false) {
-      if (E->isConceptReference()) {
-        ExprResult Res = SemaRef.SubstExpr(E, MLTAL);
-        return Res;
-      }
-      return E;
+      if (!E->isConceptReference())
+        return E;
+
+      NamedDecl *D = *E->decls_begin();
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zyn0217 wrote:

Can we assert here? (There is only a single decl which is the concept decl/TTPD)

https://github.com/llvm/llvm-project/pull/184406