[Clang][Sema] ASTContext::getUnconstrainedType propagates dependence

Author: sdkrystian

clang/docs/ReleaseNotes.rst

@@ -723,6 +723,7 @@ Bug Fixes to C++ Support
 - Clang now ignores template parameters only used within the exception specification of candidate function
   templates during partial ordering when deducing template arguments from a function declaration or when
   taking the address of a function template.
+- Fix a bug with checking constrained non-type template parameters for equivalence.
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/AST/ASTContext.cpp

@@ -5910,7 +5910,8 @@ QualType ASTContext::getUnconstrainedType(QualType T) const {
   if (auto *AT = CanonT->getAs<AutoType>()) {
     if (!AT->isConstrained())
       return T;
-    return getQualifiedType(getAutoType(QualType(), AT->getKeyword(), false,
+    return getQualifiedType(getAutoType(QualType(), AT->getKeyword(),
+                                        AT->isDependentType(),
                                         AT->containsUnexpandedParameterPack()),
                             T.getQualifiers());
   }

clang/test/CXX/temp/temp.decls/temp.fct/temp.func.order/p2.cpp

@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// expected-no-diagnostics
+
+template<typename T>
+concept C = sizeof(T) == sizeof(int);
+
+template<auto N>
+struct A;
+
+template<C auto N>
+struct A<N>;