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Add NonZeroXxx::from_mut #129
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ACP-acceptedAPI Change Proposal is accepted (seconded with no objections)API Change Proposal is accepted (seconded with no objections)T-libs-apiapi-change-proposalA proposal to add or alter unstable APIs in the standard librariesA proposal to add or alter unstable APIs in the standard libraries
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ACP-acceptedAPI Change Proposal is accepted (seconded with no objections)API Change Proposal is accepted (seconded with no objections)T-libs-apiapi-change-proposalA proposal to add or alter unstable APIs in the standard librariesA proposal to add or alter unstable APIs in the standard libraries
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Problem statement
Add a function to convert a
&mut xxxto&mut NonZeroXxx.Motivation, use-cases
My project requires working on a
&mut NonZeroU32(because onlyNonZeroU32implements a certain trait I want to use), but the value actually came from a&mut u32somewhere deep inside my data structures, so it would be inconvenient to create a separateNonZeroU32and proxy back the result later on.Solution sketches
For
n: &mut i32, if*n != 0is currently true, and we provide the aforementioned function to map this reference into a&mut NonZeroI32, since the originalncannot be dereferenced without dropping the new&mut NonZeroI32, it is safe to work with the&mut NonZeroI32directly.Links and related work
As this change is very simple, I have already implemented it in a libcore patch: rust-lang/rust#103730
What happens now?
This issue is part of the libs-api team API change proposal process. Once this issue is filed the libs-api team will review open proposals in its weekly meeting. You should receive feedback within a week or two.