ahatanak marked an inline comment as done.
ahatanak added inline comments.
================
Comment at: lib/Sema/SemaExprObjC.cpp:534
+ NSStringPointer, NSStringPointer);
+ return new (Context) ObjCBoxedExpr(SL, BoxedType, nullptr, SR);
+ }
----------------
rjmccall wrote:
> You're implicitly dropping sugar from the source expression here; I really
> think you should preserve that, and if it means you end up having to look
> through array-decay expressions, that's not the end of the world.
>
> The need for a special case here is just to allow us to compile these even if
> there isn't a boxing method available?
>
> Do you need to restrict the type of the string literal so that it doesn't
> apply to e.g. wide strings?
Line 516 checks that the pointee type has the same unqualified type as 'char'.
If the string literal inside the parentheses is of a wider type (e.g.,
`@(u"abc")`), this piece of code won't be executed, and a diagnostic is emitted
later ("illegal type 'const char16_t *' used in a boxed expression").
The original motivation for special-casing string literals inside boxed
expressions was to silence the `-Wnullable-to-nonnull-conversion` warning
mentioned here: https://oleb.net/2018/@keypath/. The warning is issued because
the return type of `stringWithUTF8String` is nullable.
```
...
+ (nullable instancetype)stringWithUTF8String:(const char
*)nullTerminatedCString;
...
NSString * _Nonnull ptr = @("abc"); // expected-error {{implicit conversion
from nullable pointer 'NSString * _Nullable' to non-nullable pointer type
'NSString * _Nonnull'}}
```
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D58729/new/
https://reviews.llvm.org/D58729
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