async/i2c: fix lifetimes on transaction() #363
Merged
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Trying to implement i2c for a shared i2c bus behind an async mutex yielded lots of cursed lifetime errors, because
&'a mut [Operation<'b>]
is invariant on'b
, not covariant as one would expect...To fix this, the GAT future needs two lifetimes. Also counterintuitively, the future must be
+ 'a
, but NOT+ 'b
. ThenAddressMode: 'static
is needed because Rust wants annoyingwhere A: 'a
bounds otherwise.The async SPI PR has the same issue, will fix later. #347
With these fixes, implementing i2c on a mutex works nicely now:
cc @matoushybl