Solve a error `.clone()` suggestion when moving a mutable reference by surechen · Pull Request #127579 · rust-lang/rust

surechen · 2024-07-10T15:25:08Z

If the moved value is a mut reference, it is used in a generic function and it's type is a generic param, suggest it can be reborrowed to avoid moving.

for example:

struct Y(u32);
// x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`.
fn generic<T>(x: T) {}

fixes #127285

rustbot · 2024-07-10T15:25:17Z

r? @lcnr

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lcnr · 2024-07-11T09:05:16Z

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

                } else {
                    (None, &[][..], 0)
                };
+                let mut reborrow = false;


Suggested change

let mut reborrow = false;

let mut suggest_reborrow = false;

Done. Thank you.

lcnr · 2024-07-11T09:09:52Z

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

                    && let node = self.infcx.tcx.hir_node_by_def_id(def_id)
                    && let Some(fn_sig) = node.fn_sig()
                    && let Some(ident) = node.ident()
                    && let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
                    && let Some(arg) = fn_sig.decl.inputs.get(pos + offset)


this only works for functions from the current crate, greatly lowering the usefulness of this new diagnostics.

You should instead be able to use tcx.fn_sig(def_id).skip_binder().skip_binder().inputs()[pos + offset].is_param()

this only works for functions from the current crate, greatly lowering the usefulness of this new diagnostics.

You should instead be able to use tcx.fn_sig(def_id).skip_binder().skip_binder().inputs()[pos + offset].is_param()

Done. Thank you.
Because is_param in

rust/compiler/rustc_middle/src/ty/sty.rs

Line 1048 in c92a8e4

pub fn is_param(self, index: u32) -> bool {

needs a arg index which I'm not sure what means, I don't use this function.

lcnr · 2024-07-11T09:12:38Z

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

+                    reborrow = is_sugg_reborrow();
+
                    let mut span: MultiSpan = arg.span.into();
                    span.push_span_label(


also I feel like we should not emit the "consider changing this parameter type in function generic to borrow instead if owning the value isn't necessary" note if a reborrow would work. so either suggest a reborrow or suggest changing the fn_sig, but not both

also I feel like we should not emit the "consider changing this parameter type in function generic to borrow instead if owning the value isn't necessary" note if a reborrow would work. so either suggest a reborrow or suggest changing the fn_sig, but not both

Done. Thank you.

bors · 2024-07-12T02:01:53Z

☔ The latest upstream changes (presumably #127614) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2024-07-16T11:35:20Z

☔ The latest upstream changes (presumably #127796) made this pull request unmergeable. Please resolve the merge conflicts.

surechen · 2024-07-16T12:12:38Z

Hello, I have made modifications, please review for me again. I received a conflict notification and I would like to resolve the conflict after approved.
Thank you @lcnr

lcnr · 2024-07-16T12:46:54Z

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

+                    }
+                    false
+                };
+                *has_suggest_reborrow = is_sugg_reborrow();


why use a closure here instead of inlining the code below into return true?

why use a closure here instead of inlining the code below into return true?

Thank you. I just think that because it's in the function suggest_ref_or_clone function, this judgment code checks a special situation and returns early, so maybe this check code could be organized into a closure. Should I abandon the closure here?

yes, abandon the closure

yes, abandon the closure

Done. Thank you.

…on and it's type is a generic param, it can be reborrowed to avoid moving. for example: ```rust struct Y(u32); // x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`. fn generic<T>(x: T) {} ``` fixes rust-lang#127285

lcnr · 2024-07-17T11:19:45Z

@bors r+ rollup

bors · 2024-07-17T11:19:47Z

📌 Commit 4821b84 has been approved by lcnr

It is now in the queue for this repository.

…iaskrgr Rollup of 8 pull requests Successful merges: - rust-lang#125042 (Use ordinal number in argument error) - rust-lang#127229 (rustdoc: click target for sidebar items flush left) - rust-lang#127337 (Move a few intrinsics to Rust abi) - rust-lang#127472 (MIR building: Stop using `unpack!` for `BlockAnd<()>`) - rust-lang#127579 (Solve a error `.clone()` suggestion when moving a mutable reference) - rust-lang#127769 (Don't use implicit features in `Cargo.toml` in `compiler/`) - rust-lang#127844 (Remove invalid further restricting suggestion for type bound) - rust-lang#127855 (Add myself to review rotation) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#127579 - surechen:fix_127285, r=lcnr Solve a error `.clone()` suggestion when moving a mutable reference If the moved value is a mut reference, it is used in a generic function and it's type is a generic param, suggest it can be reborrowed to avoid moving. for example: ```rust struct Y(u32); // x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`. fn generic<T>(x: T) {} ``` fixes rust-lang#127285

Dedup `&mut *` reborrow suggestion in loops rust-lang#73534 added a reborrow suggestion in loops; rust-lang#127579 generalized this to generic parameters, making the suggestion triggers twice: ```rs use std::io::Read; fn decode_scalar(_reader: impl Read) {} fn decode_array(reader: &mut impl Read) { for _ in 0.. { decode_scalar(reader); } } ``` ``` error[E0382]: use of moved value: `reader` --> src/lib.rs:6:23 | 4 | fn decode_array(reader: &mut impl Read) { | ------ move occurs because `reader` has type `&mut impl Read`, which does not implement the `Copy` trait 5 | for _ in 0.. { | ------------ inside of this loop 6 | decode_scalar(reader); | ^^^^^^ value moved here, in previous iteration of loop | help: consider creating a fresh reborrow of `reader` here | 6 | decode_scalar(&mut *reader); | ++++++ help: consider creating a fresh reborrow of `reader` here | 6 | decode_scalar(&mut *reader); | ++++++ ``` This PR removes the suggestion in loops, as it requires generic parameters anyway (i.e., the reborrow is automatic if there is no generic params). `@rustbot` label +A-borrow-checker +A-diagnostics +A-suggestion-diagnostics +D-papercut

Rollup merge of rust-lang#138462 - ShE3py:mut-borrow-in-loop, r=oli-obk Dedup `&mut *` reborrow suggestion in loops rust-lang#73534 added a reborrow suggestion in loops; rust-lang#127579 generalized this to generic parameters, making the suggestion triggers twice: ```rs use std::io::Read; fn decode_scalar(_reader: impl Read) {} fn decode_array(reader: &mut impl Read) { for _ in 0.. { decode_scalar(reader); } } ``` ``` error[E0382]: use of moved value: `reader` --> src/lib.rs:6:23 | 4 | fn decode_array(reader: &mut impl Read) { | ------ move occurs because `reader` has type `&mut impl Read`, which does not implement the `Copy` trait 5 | for _ in 0.. { | ------------ inside of this loop 6 | decode_scalar(reader); | ^^^^^^ value moved here, in previous iteration of loop | help: consider creating a fresh reborrow of `reader` here | 6 | decode_scalar(&mut *reader); | ++++++ help: consider creating a fresh reborrow of `reader` here | 6 | decode_scalar(&mut *reader); | ++++++ ``` This PR removes the suggestion in loops, as it requires generic parameters anyway (i.e., the reborrow is automatic if there is no generic params). `@rustbot` label +A-borrow-checker +A-diagnostics +A-suggestion-diagnostics +D-papercut

rustbot assigned lcnr Jul 10, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 10, 2024

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surechen changed the title ~~Solve error .clone() suggestion when moving a mutable reference~~ [WIP] Solve error .clone() suggestion when moving a mutable reference Jul 10, 2024

surechen changed the title ~~[WIP] Solve error .clone() suggestion when moving a mutable reference~~ [WIP] Solve a error .clone() suggestion when moving a mutable reference Jul 11, 2024

surechen force-pushed the fix_127285 branch from 7739079 to eb11798 Compare July 11, 2024 04:36

surechen changed the title ~~[WIP] Solve a error .clone() suggestion when moving a mutable reference~~ Solve a error .clone() suggestion when moving a mutable reference Jul 11, 2024

lcnr reviewed Jul 11, 2024

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surechen force-pushed the fix_127285 branch 2 times, most recently from 2b60569 to 1f78e60 Compare July 11, 2024 15:45

surechen requested a review from lcnr July 11, 2024 15:49

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surechen changed the title ~~Solve a error .clone() suggestion when moving a mutable reference~~ [WIP] Solve a error .clone() suggestion when moving a mutable reference Jul 12, 2024

surechen force-pushed the fix_127285 branch from 1f78e60 to 85c6150 Compare July 12, 2024 14:47

surechen changed the title ~~[WIP] Solve a error .clone() suggestion when moving a mutable reference~~ Solve a error .clone() suggestion when moving a mutable reference Jul 12, 2024

lcnr reviewed Jul 16, 2024

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surechen force-pushed the fix_127285 branch from 85c6150 to 4821b84 Compare July 17, 2024 02:10

surechen requested a review from lcnr July 17, 2024 02:59

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 17, 2024

matthiaskrgr mentioned this pull request Jul 17, 2024

Rollup of 8 pull requests #127865

Merged

bors merged commit 23dd3a0 into rust-lang:master Jul 18, 2024

rustbot added this to the 1.81.0 milestone Jul 18, 2024

matthiaskrgr mentioned this pull request Jul 18, 2024

conflicting errors: index out of bounds #127915

Closed

ShE3py mentioned this pull request Mar 13, 2025

Dedup &mut * reborrow suggestion in loops #138462

Merged

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surechen commented Jul 10, 2024

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bors commented Jul 12, 2024

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lcnr commented Jul 17, 2024

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