[PATCH] D22391: [Sema] Add warning for implicitly casting a null constant to a non null pointer type

[Akira Hatanaka via cfe-commits]

ahatanak created this revision.
ahatanak added a reviewer: doug.gregor.
ahatanak added a subscriber: cfe-commits.

This patch makes clang issue a warning when a null constant is used in a context where a non null expression is expected. For example:

```
int * _Nonnull p0 = 0; // warning expected here
int * _Nonnull p1;
int * _Nonnull p2 = c ? p1 : 0; // warning expected here
```

A new function Sema::diagnoseNullPtrToNonnullCast is defined, which checks whether a null pointer constant is being cast to a _Nonnull pointer type, and called before ImplicitCastExprs are created.

rdar://problem/24724255
rdar://problem/22074116



https://reviews.llvm.org/D22391

Files:
  include/clang/Basic/DiagnosticSemaKinds.td
  include/clang/Sema/Sema.h
  lib/Sema/Sema.cpp
  lib/Sema/SemaExpr.cpp
  test/Sema/nullability.c
  test/SemaCXX/nullability.cpp

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