[llvm-branch-commits] [clang] release/22.x: [clang][AST] Fix assertion in `getFullyQualifiedType` for AutoType (#186105) (PR #186882)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/186882

Backport 86c4e96

Requested by: @devajithvs

>From 56bf6b4ba84ccfaf3325dced797a1a9f45ebb677 Mon Sep 17 00:00:00 2001
From: Devajith <devajith.valaparambil.sreeramaswamy at cern.ch>
Date: Thu, 12 Mar 2026 14:23:50 +0100
Subject: [PATCH] [clang][AST] Fix assertion in `getFullyQualifiedType` for
 AutoType (#186105)

getFullyQualifiedType() asserts "Unhandled type node" when the input
QualType is an AutoType.

This was exposed by clang-repl's value printer:
```
clang-repl> namespace N { struct D {}; }
clang-repl> auto x = N::D(); x // asserts
```

Strip AutoType early before the type-specific handling.

(cherry picked from commit 86c4e96856a645a4015adf0e4d1a779e5662c6ca)
---
 clang/lib/AST/QualTypeNames.cpp         | 5 +++++
 clang/test/Interpreter/pretty-print.cpp | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/clang/lib/AST/QualTypeNames.cpp b/clang/lib/AST/QualTypeNames.cpp
index 191841649a86f..9e3885e100c6b 100644
--- a/clang/lib/AST/QualTypeNames.cpp
+++ b/clang/lib/AST/QualTypeNames.cpp
@@ -369,6 +369,11 @@ NestedNameSpecifier createNestedNameSpecifier(const ASTContext &Ctx,
 /// versions of any template parameters.
 QualType getFullyQualifiedType(QualType QT, const ASTContext &Ctx,
                                bool WithGlobalNsPrefix) {
+  // Use the underlying deduced type for AutoType
+  if (const auto *AT = dyn_cast<AutoType>(QT.getTypePtr()))
+    if (AT->isDeduced())
+      QT = AT->getDeducedType();
+
   // In case of myType* we need to strip the pointer first, fully
   // qualify and attach the pointer once again.
   if (isa<PointerType>(QT.getTypePtr())) {
diff --git a/clang/test/Interpreter/pretty-print.cpp b/clang/test/Interpreter/pretty-print.cpp
index bad71cdd48f0b..f0548358d65db 100644
--- a/clang/test/Interpreter/pretty-print.cpp
+++ b/clang/test/Interpreter/pretty-print.cpp
@@ -60,6 +60,15 @@ struct S5 { int foo() { return 42; }};
 &S5::foo
 // CHECK-NEXT: (int (S5::*)()) Function @0x{{[0-9a-f]+}}
 
+// Namespaced types deduced via auto
+namespace Outer { struct Foo {}; }
+auto x = Outer::Foo(); x
+// CHECK-NEXT: (Outer::Foo &) @0x{{[0-9a-f]+}}
+
+namespace Outer { template<class T> struct Bar {}; }
+auto y = Outer::Bar<int>(); y
+// CHECK-NEXT: (Outer::Bar<int> &) @0x{{[0-9a-f]+}}
+
 // int i = 12;
 // int &iref = i;
 // iref