Evaluate within a coroutine an expression which results in a type matching the following customisation points, emitting the
T if successful, immediately returning
from the calling function if unsuccessful:
Default overloads for these customisation points are provided. See the recipe for supporting foreign input to
Hints are given to the compiler that the expression will be unsuccessful. If you expect success, you should use
An internal temporary to hold the value of the expression is created, which generally invokes a copy/move. If you wish to never copy/move, you can tell this macro to create the internal temporary as a reference instead.
Availability: GCC and clang only. Use
#ifdef OUTCOME_CO_TRYX to determine if available.
Overridable: Not overridable.
for most of the mechanics.
This macro makes use of a proprietary extension in GCC and clang to emit the
T from a successful expression. You can thus use
OUTCOME_CO_TRYX(expr) directly in expressions e.g.
auto x = y + OUTCOME_CO_TRYX(foo(z));.
Be aware there are compiler quirks in preserving the rvalue/lvalue/etc-ness of emitted
T’s, specifically copy or move constructors may be called unexpectedly and/or copy elision not work as expected. If these prove to be problematic, use