allow deref patterns to move out of boxes #140022
Open
+221
−82
Conversation
This file contains 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
Since deref patterns on boxes will be lowered differently, I'll be making a separate test file for them. This makes sure we're still testing the generic `Deref(Mut)::deref(_mut)`-based lowering.
This allows deref patterns to move out of boxes. Implementation-wise, I've opted to put the information of whether a deref pattern uses a built-in deref or a method call in the THIR. It'd be a bit less code to check `.is_box()` everywhere, but I think this way feels more robust (and we don't have a `mutability` field in the THIR that we ignore when the smart pointer's a box). I'm not sure about the naming (or using `ByRef`), though.
rustbot
added
S-waiting-on-review
|
Some changes occurred in match lowering cc @Nadrieril Some changes occurred in match checking cc @Nadrieril |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
This adds a case to lower deref patterns on boxes using a built-in deref instead of a
Deref::dereforDerefMut::deref_mutcall: ifderef!(inner): Box<T>is matching on placeplace, the inner patterninnernow matches on*placerather than a temporary. No longer needing to call a method also means it won't borrow the scrutinee in match arms. This allows for bindings ininnerto move out of*place.For comparison with box patterns, this uses the same MIR lowering but different THIR. Consequently, deref patterns on boxes are treated the same as any other deref patterns in match exhaustiveness analysis. Box patterns can't quite be implemented in terms of deref patterns until exhaustiveness checking for deref patterns is implemented (I'll open a PR for exhaustiveness soon!).
Tracking issue: #87121
r? @Nadrieril