ptr_cast_constness: check for implicit mut to const pointer coercion
#15747
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changelog: [`ptr_cast_constness`]: check for implicit mut to const pointer coercion Signed-off-by: Zihan <[email protected]>
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Lintcheck changes for cec69cd
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In my opinion, if we start linting this pattern, it should be a new lint.
ptr_cast_constness is specifically about as casts. The motivation is that it's easy to unintentionally also change the pointee type alongside with constness with normal as casts, so like accidentally going from *mut i32 to *const i64.
This is not true for implicit coercions like what is proposed. That can only ever go from *mut T to *const T without changing the pointee and seems entirely harmless to me. Looking at the lintcheck results, I'm also not too convinced that it adds much value.
It should then likely also be a restriction lint given that there's IMO not really any advantage, just forces the user to be more explicit.
I'll also open a thread on zulip soon to gather some other opinions.
Fixes #13667
changelog: [
ptr_cast_constness]: check for implicit mut to const pointer coercion