Change destructuring assignment lowering to use match.
#96588
Closed
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
Previously, `(a, b) = t` produced code like `{ let (lhs1, lhs2) = t; a = lhs1; b = lhs2; }`,
with this commit instead we produce `match t { (lhs1, lhs2) => { a = lhs1; b = lhs2; } }`.
The desired effect is to make sure that temporaries in the expression `t` aren't dropped too early,
in order to get better consistency between the behavior of e.g. `x = t` vs. `[x] = [t]` or `(x,) = (t,)`
(where `t` is an arbitrary expression).
rustbot
added
the
T-compiler
|
r? @oli-obk (rust-highfive has picked a reviewer for you, use r? to override) |
rust-highfive
added
the
S-waiting-on-review
|
The job Click to see the possible cause of the failure (guessed by this bot) |
|
@bors try |
|
⌛ Trying commit 33eac80 with merge 37c8ca9437b76fdac722d51b7bfac3893dc01c1c... |
|
☀️ Try build successful - checks-actions |
|
@craterbot test |
|
🚨 Error: failed to parse the command 🆘 If you have any trouble with Crater please ping |
|
Trying to address the diagnostics change that causes CI failure, I found that the current logic is flawed leading to code like this ICEing on current nightly fn main() {
let x: usize;
while (x,) = (0_usize,) {}
}I’ll come back to this (and open another issue, etc…) tomorrow. |
oli-obk
added
S-waiting-on-author
|
Ping from triage: |
rustbot
added
the
S-inactive
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Outdated suggestions cannot be applied.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.
Previously, lowering
(a, b) = tproduced code like{ let (lhs1, lhs2) = t; a = lhs1; b = lhs2; },with this PR,
match t { (lhs1, lhs2) => { a = lhs1; b = lhs2; } }is produced instead.The desired effect is to make sure that temporaries in the expression
taren't dropped too early,in order to get better consistency between the behavior of e.g.
x = tvs.[x] = [t]or(x,) = (t,)(where
tis an arbitrary expression).Fixes #96579
As also discussed shortly here, this is a breaking change (most commonly affecting drop order of temporaries of the RHS vs. old values in the places that are being assigned) and thus this will need a crater run, and probably approval from T-lang.
The PR is still missing tests at this point. And there's a
FIXMEto be addressed/discussed (though theFIXMEis no blocker for a crater run, as AFAICT – in anything – it could only affect diagnostics).