Andrew Trick c9033ed938 Add a SIL attribute [without_actually_escaping]. ...

ConvertFunction and reabstraction thunks need this attribute. Otherwise,
there is no way to identify that withoutActuallyEscaping was used
to explicitly perform a conversion.

The destination of a [without_actually_escaping] conversion always has
an escaping function type. The source may have either an escaping or
@noescape function type. The conversion itself may be a nop, and there
is nothing distinctive about it. The thing that is special about these
conversions is that the source function type may have unboxed
captures. i.e. they have @inout_aliasable parameters. Exclusivity
requires that the compiler enforce a SIL data flow invariant that
nonescaping closures with unboxed captures can never be stored or
passed as an @escaping function argument. Adding this attribute allows
the compiler to enforce the invariant in general with an escape hatch
for withoutActuallyEscaping.

2018-08-14 17:14:25 -07:00

50 KiB

Raw Blame History

View Raw