[PATCH] D142799: [Clang] Fix unconditional access to Attr pointer when checking if _Nullable is applicable to a type

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik created this revision.
shafik added reviewers: aaron.ballman, erichkeane.
Herald added a project: All.
shafik requested review of this revision.

In `TransformAttributedType(...)` when checking if `_Nullable` can be applied to a type it dereferences `TL.getAttr()` unconditionally which we can see from the code earlier in the function is not correct since it is expected to be `nullptr` in some cases.

It looks like the correct course of action is to use `TL.getModifiedLoc()` over `TL.getAttr()->getLocation()` in the case that `TL.getAttr()` returns a `nullptr`.

Fixes: https://github.com/llvm/llvm-project/issues/60344


https://reviews.llvm.org/D142799

Files:
  clang/lib/Sema/TreeTransform.h
  clang/test/SemaCXX/nullability.cpp


Index: clang/test/SemaCXX/nullability.cpp
===================================================================
--- clang/test/SemaCXX/nullability.cpp
+++ clang/test/SemaCXX/nullability.cpp
@@ -136,3 +136,9 @@
 void testNullabilityCompletenessWithTemplate() {
   Template<int*> tip;
 }
+
+namespace GH60344 {
+class a;
+template <typename b> using c = b _Nullable; // expected-error {{'_Nullable' cannot be applied to non-pointer type 'GH60344::a'}}
+c<a>;  // expected-note {{in instantiation of template type alias 'c' requested here}}
+}
Index: clang/lib/Sema/TreeTransform.h
===================================================================
--- clang/lib/Sema/TreeTransform.h
+++ clang/lib/Sema/TreeTransform.h
@@ -6992,7 +6992,8 @@
     // type sugar, and therefore cannot be diagnosed in any other way.
     if (auto nullability = oldType->getImmediateNullability()) {
       if (!modifiedType->canHaveNullability()) {
-        SemaRef.Diag(TL.getAttr()->getLocation(),
+        SemaRef.Diag((TL.getAttr() ? TL.getAttr()->getLocation()
+                                   : TL.getModifiedLoc().getBeginLoc()),
                      diag::err_nullability_nonpointer)
             << DiagNullabilityKind(*nullability, false) << modifiedType;
         return QualType();


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