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ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow #87069

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merged 5 commits into from
Jul 16, 2021
Merged

ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow #87069

merged 5 commits into from
Jul 16, 2021

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arora-aman
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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 11, 2021
nikomatsakis
nikomatsakis requested changes Jul 12, 2021
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compiler/rustc_typeck/src/expr_use_visitor.rs Outdated
match mode {
ConsumeMode::Move => self.delegate.consume(place_with_id, diag_expr_id, mode),
ConsumeMode::Copy => {
self.delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
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Hmm, I had expected to make this change within the upvar delegate, and not the ExprUseVisitor. It seems potentially useful to some clients to know that this was a "by-value copy" -- I think there is other code in clippy that uses this, for example.

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Otherwise we should just remove the ConsumeMode

nikomatsakis
nikomatsakis requested changes Jul 14, 2021
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Suggested edit to the comment, and a simplification

compiler/rustc_typeck/src/expr_use_visitor.rs Outdated
Comment on lines 29 to 35
// The value found at `place` is moved, depending
// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
//
// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
// id will be the id of the expression `expr` but the place itself will have
// the id of the binding in the pattern `pat`.
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Suggested change
// The value found at `place` is moved, depending
// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
//
// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
// id will be the id of the expression `expr` but the place itself will have
// the id of the binding in the pattern `pat`.
// The value found at `place` is moved, meaning that it is used by value
// and is not known to have `Copy` type.
//
// If a value is used by value but *does* have `Copy` type, that is treated as a
// "shared borrow". This corresponds to the minimal access that a closure needs
// to perform that operation (a shared reference).
//
// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
// id will be the id of the expression `expr` but the place itself will have
// the id of the binding in the pattern `pat`.

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I didn't add the detail about closures because ExprUseVisitor and therefore this delegate is used in other contexts too

compiler/rustc_typeck/src/expr_use_visitor.rs Outdated
Comment on lines 656 to 664
let mode = copy_or_move(mc, &place);
match mode {
ConsumeMode::Move => delegate.consume(place, discr_place.hir_id),
ConsumeMode::Copy => delegate.borrow(
place,
discr_place.hir_id,
ty::BorrowKind::ImmBorrow,
),
}
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Suggested change
let mode = copy_or_move(mc, &place);
match mode {
ConsumeMode::Move => delegate.consume(place, discr_place.hir_id),
ConsumeMode::Copy => delegate.borrow(
place,
discr_place.hir_id,
ty::BorrowKind::ImmBorrow,
),
}
self.delegate_consume(place, discr_place.hir_id);

Does this not work?

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we need 2229 enabled to make this work 🙃. The closure is passed to self.mc. I'll just refactor into a helper.

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@bors r+

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bors commented Jul 15, 2021

📌 Commit 75291ee has been approved by nikomatsakis

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 15, 2021
GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request Jul 15, 2021
@GuillaumeGomez
Rollup merge of rust-lang#87069 - sexxi-goose:copy_ref_always, r=niko…
5dd7ca3 
…matsakis

ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow

r? `@nikomatsakis`
@GuillaumeGomez GuillaumeGomez mentioned this pull request Jul 15, 2021
Closed
GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request Jul 15, 2021
@GuillaumeGomez
Rollup merge of rust-lang#87069 - sexxi-goose:copy_ref_always, r=niko…
8a8b285 
…matsakis

ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow

r? ``@nikomatsakis``
@GuillaumeGomez GuillaumeGomez mentioned this pull request Jul 15, 2021
Closed
@GuillaumeGomez GuillaumeGomez mentioned this pull request Jul 16, 2021
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Jul 16, 2021
@bors
Auto merge of rust-lang#87182 - GuillaumeGomez:rollup-whwohua, r=Guil…
59d92bd 
…laumeGomez

Rollup of 7 pull requests

Successful merges:

 - rust-lang#86983 (Add or improve natvis definitions for common standard library types)
 - rust-lang#87069 (ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow)
 - rust-lang#87138 (Correct invariant documentation for `steps_between`)
 - rust-lang#87145 (Make --cap-lints and related options leave crate hash alone)
 - rust-lang#87161 (RFC2229: Use the correct place type)
 - rust-lang#87162 (Fix type decl layout "overflow")
 - rust-lang#87167 (Fix sidebar display on small devices)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit c1ffca0 into rust-lang:master Jul 16, 2021
@rustbot rustbot added this to the 1.55.0 milestone Jul 16, 2021
flip1995 pushed a commit to flip1995/rust that referenced this pull request Jul 19, 2021
@GuillaumeGomez
Rollup merge of rust-lang#87069 - sexxi-goose:copy_ref_always, r=niko…
5c54d04 
…matsakis

ExprUseVisitor: Treat ByValue use of Copy types as ImmBorrow

r? ```@nikomatsakis```
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