Replace transmute! macro with transmute fn
#190
Draft
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
jswrenn
force-pushed
the
more-transmute-ui-tests
branch
4 times, most recently
from
665ddc1 to
59917e3
Compare
As a consequence of this change, the phase in which some invalid transmutes are detected differs. The `transmute!` macro depended internally on `mem::transmute`, which cannot be used in generic contexts but provides pre-monomorphization errors if the source and destination types have different sizes. By contrast, the `transmute` function can be used in generic contexts, but does not report size errors until monomorphization. This increase in expressivity comes at the cost of some usability: size errors are currently only reported by invocations of `cargo build`; not `cargo check`.
kupiakos
reviewed
Jul 21, 2023
| // Used in `transmute!` below. | ||
| #[doc(hidden)] | ||
| pub use core::mem::transmute as __real_transmute; | ||
| pub trait TransmuteFrom<Src>: Sized { |
Contributor
There was a problem hiding this comment.
This trait does not need to be (and shouldn't be) pub, because it has a blanket implementation on T: Sized that transmute can use without declaring it in its where bounds.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
As a consequence of this change, the phase in which some invalid transmutes are detected differs. The
transmute!macro depended internally onmem::transmute, which cannot be used in generic contexts but provides pre-monomorphization errors if the source and destination types have different sizes. By contrast, thetransmutefunction can be used in generic contexts, but does not report size errors until monomorphization.This increase in expressivity comes at the cost of some usability: size errors are currently only reported by invocations of
cargo build; notcargo check.