Correctly document CTFE behavior of is_null and methods that call is_null. #134325
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I have rewritten the comment to be hopefully easier to understand. Hopefully this wording doesn't commit rust to any guarantees that we don't want to make? |
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The "panic in const if CTFE doesn't know the answer" behavior was discussed to be the desired behavior in rust-lang#74939, and is currently how the function actually behaves. I intentionally wrote this documentation to allow for the possibility that a panic might not occur even if the pointer is out of bounds, because of rust-lang#133700 and other potential changes in the future.
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I have applied RalfJung's proposed wording changes. I've also edited the "Behavior during const evaluation" heading to "Panics during const evaluation", and made it a level 1 heading, to match the typical "Panics" heading. Does this need a beta backport, since the is_null methods are const-stabilized in beta? |
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There are a bunch of |
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LGTM, thanks :) @bors r+ rollup |
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The "panic in const if CTFE doesn't know the answer" behavior was discussed to be the desired behavior in #74939, and is currently how the function actually behaves.
I intentionally wrote this documentation to allow for the possibility that a panic might not occur even if the pointer is out of bounds, because of #133700 and other potential changes in the future.
This is beta-nominated since
const fn is_nullstabilization is in beta already but the docs there are wrong, and it seems better to have the docs be correct at the time of stabilization.