[PATCH] D156728: [Sema] Ignore nullability qualifiers when deducing types for `auto` and `__auto_type`

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak created this revision.
ahatanak added reviewers: doug.gregor, rjmccall.
ahatanak added a project: clang.
Herald added a project: All.
ahatanak requested review of this revision.

Prior to https://reviews.llvm.org/D110216, the deduced types didn't inherit the nullability qualifiers of the initializer expressions. This patch restores the previous behavior.

See https://developer.apple.com/forums/thread/726000#726000021 for background.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156728

Files:
  clang/lib/Sema/SemaTemplateDeduction.cpp
  clang/test/Sema/nullability.c
  clang/test/SemaCXX/nullability.cpp


Index: clang/test/SemaCXX/nullability.cpp
===================================================================
--- clang/test/SemaCXX/nullability.cpp
+++ clang/test/SemaCXX/nullability.cpp
@@ -137,6 +137,21 @@
   Template<int*> tip;
 }
 
+namespace test_auto {
+
+template <class T>
+void foo(T t) {
+  int * _Nonnull x = t; // OK.
+}
+
+void test(int * _Nullable ptr) {
+  auto b = ptr; // _Nullable on ptr is ignored when b's type is deduced.
+  int * _Nonnull c = b; // OK.
+  foo(ptr); // _Nullable on ptr is ignored when T's type is deduced.
+}
+
+}
+
 namespace GH60344 {
 class a;
 template <typename b> using c = b _Nullable; // expected-error {{'_Nullable' cannot be applied to non-pointer type 'GH60344::a'}}
Index: clang/test/Sema/nullability.c
===================================================================
--- clang/test/Sema/nullability.c
+++ clang/test/Sema/nullability.c
@@ -125,9 +125,11 @@
   int *a = ptr; // okay
   _Nonnull int *b = ptr; // expected-warning{{implicit conversion from nullable pointer 'int * _Nullable' to non-nullable pointer type 'int * _Nonnull'}}
   b = ptr; // expected-warning{{implicit conversion from nullable pointer 'int * _Nullable' to non-nullable pointer type 'int * _Nonnull'}}
-  __auto_type _Nonnull c = ptr; // expected-warning{{implicit conversion from nullable pointer 'int * _Nullable' to non-nullable pointer type 'int * _Nullable _Nonnull'}}
+  __auto_type _Nonnull c = ptr; // expected-warning{{implicit conversion from nullable pointer 'int * _Nullable' to non-nullable pointer type 'int * _Nonnull'}}
 
   accepts_nonnull_1(ptr); // expected-warning{{implicit conversion from nullable pointer 'int * _Nullable' to non-nullable pointer type 'int * _Nonnull'}}
+  __auto_type d = ptr; // _Nullable on ptr is ignored when d's type is deduced.
+  b = d; // OK.
 }
 
 // Check nullability of conditional expressions.
Index: clang/lib/Sema/SemaTemplateDeduction.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateDeduction.cpp
+++ clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3879,8 +3879,11 @@
   // C++0x [temp.deduct.call]p3:
   //   If P is a cv-qualified type, the top level cv-qualifiers of P's type
   //   are ignored for type deduction.
-  if (ParamType.hasQualifiers())
+  // Ignore top level nullability qualifiers too.
+  if (ParamType.hasQualifiers()) {
     ParamType = ParamType.getUnqualifiedType();
+    (void)AttributedType::stripOuterNullability(ParamType);
+  }
 
   //   [...] If P is a reference type, the type referred to by P is
   //   used for type deduction.
@@ -3927,7 +3930,9 @@
     else {
       // - If A is a cv-qualified type, the top level cv-qualifiers of A's
       //   type are ignored for type deduction.
+      // Ignore top level nullability qualifiers too.
       ArgType = ArgType.getUnqualifiedType();
+      (void)AttributedType::stripOuterNullability(ArgType);
     }
   }
 


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