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

[Younan Zhang via cfe-commits]

================
@@ -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();
+      ConceptDecl *ResolvedConcept = nullptr;
+
+      if (const auto * const TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
+        const auto Depth = TTP->getDepth();
+        const auto Pos = TTP->getPosition();
----------------
zyn0217 wrote:

```suggestion
        unsigned Depth = TTP->getDepth();
        unsigned Pos = TTP->getPosition();
```

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