Suggest const_mut_refs
, not const_fn
for mutable references in const fn
#77136
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Resolves #77134.
Prior to #76850, most uses of
&mut
inconst fn
requiredinvolved two feature gates,const_mut_refs
andconst_fn
. The first allowed all mutable borrows of locals. The second allowed only locals, arguments and return values whose types contained&mut
. I switched the second check to theconst_mut_refs
gate. However, I forgot update the error message with the new suggestion.Alternatively, we could revert to having two different feature gates for this. OP's code never borrows anything mutably, so it didn't need
const_mut_refs
in the past, onlyconst_fn
. I'd prefer to keep everything under a single gate, however.r? @oli-obk