[clang] [Sema] Handle AttributedType in template deduction with derived-to-base conversions (PR #134361)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Ilya Biryukov (ilya-biryukov)

<details>
<summary>Changes</summary>

Fix #<!-- -->134356.

We accidentally skipped checking derived-to-base conversions because deduction did not strip sugar in the relevant code. This caused deduction failures when a parameter type had an attribute.

---
Full diff: https://github.com/llvm/llvm-project/pull/134361.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaTemplateDeduction.cpp (+1-1) 
- (added) clang/test/Sema/nullability-and-template-deduction.cpp (+16) 


``````````diff
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 9969f1762fe36..92283867c38cd 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4446,7 +4446,7 @@ static bool AdjustFunctionParmAndArgTypesForDeduction(
   //       transformed A can be a pointer to a derived class pointed to by
   //       the deduced A.
   if (isSimpleTemplateIdType(ParamType) ||
-      (isa<PointerType>(ParamType) &&
+      (ParamType->getAs<PointerType>() &&
        isSimpleTemplateIdType(
            ParamType->castAs<PointerType>()->getPointeeType())))
     TDF |= TDF_DerivedClass;
diff --git a/clang/test/Sema/nullability-and-template-deduction.cpp b/clang/test/Sema/nullability-and-template-deduction.cpp
new file mode 100644
index 0000000000000..3ea6d38d26b69
--- /dev/null
+++ b/clang/test/Sema/nullability-and-template-deduction.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -fsyntax-only %s -verify
+// expected-no-diagnostics
+
+template <class T> struct Base {};
+template <class T> struct Derived : Base<T> {};
+
+template <class T> void foo(Base<T> *_Nonnull);
+
+template <class T> void bar(Base<T> *);
+
+
+void test() {
+    Derived<int> d;
+    foo(&d);
+    bar(&d);
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/134361