Skip to content

On borrow return type, suggest borrowing from arg or owned return type#117914

Merged
bors merged 9 commits intorust-lang:masterfrom
estebank:issue-85843
Dec 12, 2023
Merged

On borrow return type, suggest borrowing from arg or owned return type#117914
bors merged 9 commits intorust-lang:masterfrom
estebank:issue-85843

Conversation

@estebank
Copy link
Contributor

@estebank estebank commented Nov 14, 2023

When we encounter a function with a return type that has an anonymous lifetime with no argument to borrow from, besides suggesting the 'static lifetime we now also suggest changing the arguments to be borrows or changing the return type to be an owned type.

error[E0106]: missing lifetime specifier
  --> $DIR/variadic-ffi-6.rs:7:6
   |
LL | ) -> &usize {
   |      ^ expected named lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
   |
LL | ) -> &'static usize {
   |       +++++++
help: instead, you are more likely to want to change one of the arguments to be borrowed...
   |
LL |     x: &usize,
   |        +
help: ...or alternatively, to want to return an owned value
   |
LL - ) -> &usize {
LL + ) -> usize {
   |

Fix #85843.

@rustbot
Copy link
Collaborator

rustbot commented Nov 14, 2023

r? @wesleywiser

(rustbot has picked a reviewer for you, use r? to override)

@rustbot 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 Nov 14, 2023
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rustbot rustbot added A-testsuite Area: The testsuite used to check the correctness of rustc T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Nov 14, 2023
@bors

This comment was marked as resolved.

Sign in to view
@estebank estebank force-pushed the issue-85843 branch 2 times, most recently from 61bc7d1 to 3e26c52 Compare November 16, 2023 16:55
@bors
Copy link
Collaborator

bors commented Nov 19, 2023

☔ The latest upstream changes (presumably #117683) made this pull request unmergeable. Please resolve the merge conflicts.

@estebank
On borrow return type, suggest borrowing from arg or owned return type
b7a23bc 
When we encounter a function with a return type that has an anonymous
lifetime with no argument to borrow from, besides suggesting the
`'static` lifetime we now also suggest changing the arguments to be
borrows or changing the return type to be an owned type.

```
error[E0106]: missing lifetime specifier
  --> $DIR/variadic-ffi-6.rs:7:6
   |
LL | ) -> &usize {
   |      ^ expected named lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
   |
LL | ) -> &'static usize {
   |       +++++++
help: instead, you are more likely to want to change one of the arguments to be borrowed...
   |
LL |     x: &usize,
   |        +
help: ...or alternatively, to want to return an owned value
   |
LL - ) -> &usize {
LL + ) -> usize {
   |
```

Fix rust-lang#85843.
@estebank
Account for impl Trait in lifetime suggestion
5fce361 
When encountering
```rust
fn g(mut x: impl Iterator<Item = &()>) -> Option<&()> { /* */ }
```
Suggest
```rust
fn g<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&'a ()> { /* */ }
```
@estebank
Tweak wording
d30252e
@estebank
Fix incorrect lifetime suggestion
dec7f00
@estebank
Suggest 'a when trait object assoc type has '_
2a92d82
@estebank
Account for '_ in lifetime suggestion
85f26ad
@estebank
Do not consider traits as ownable in suggestion
bb9d720
@estebank
Rely in resolve and not on path name for &str -> String suggestion
02bea16
@estebank
let-chain fmt
eee4cc6
wesleywiser
wesleywiser reviewed Nov 22, 2023
View reviewed changes
compiler/rustc_resolve/src/late/diagnostics.rs
Comment on lines +2957 to +2958
", but this is uncommon unless you're returning a borrowed value from a \
`const` or a `static`{owned}",
Copy link
Member

@wesleywiser wesleywiser Nov 22, 2023

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should we make these messages translatable?

Copy link
Contributor Author

@estebank estebank Nov 23, 2023

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We should, but I didn't want to make the PR too big to review.

@wesleywiser
Copy link
Member

wesleywiser commented Dec 12, 2023

@bors r+

@bors
Copy link
Collaborator

bors commented Dec 12, 2023

📌 Commit eee4cc6 has been approved by wesleywiser

It is now in the queue for this repository.

@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 Dec 12, 2023
@matthiaskrgr matthiaskrgr mentioned this pull request Dec 12, 2023
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Dec 12, 2023
@bors
Auto merge of rust-lang#118881 - matthiaskrgr:rollup-0rl3tir, r=matth…
028b6d1 
…iaskrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang#116740 (dont ICE when ConstKind::Expr for is_const_evaluatable)
 - rust-lang#117914 (On borrow return type, suggest borrowing from arg or owned return type)
 - rust-lang#117927 (Clarify how to choose a FutureIncompatibilityReason variant.)
 - rust-lang#118855 (Improve an error involving attribute values.)
 - rust-lang#118856 (rustdoc-search: clean up parser)
 - rust-lang#118865 (rustc_codegen_llvm: Enforce `rustc::potential_query_instability` lint)
 - rust-lang#118866 (llvm-wrapper: adapt for LLVM API change)
 - rust-lang#118868 (Correctly gate the parsing of match arms without body)
 - rust-lang#118877 (tests: CGU tests require build-pass, not check-pass (remove FIXME))

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit ffdb471 into rust-lang:master Dec 12, 2023
@rustbot rustbot added this to the 1.76.0 milestone Dec 12, 2023
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Dec 12, 2023
@rust-timer
Unrolled build for rust-lang#117914
f9c6bbf 
Rollup merge of rust-lang#117914 - estebank:issue-85843, r=wesleywiser

On borrow return type, suggest borrowing from arg or owned return type

When we encounter a function with a return type that has an anonymous lifetime with no argument to borrow from, besides suggesting the `'static` lifetime we now also suggest changing the arguments to be borrows or changing the return type to be an owned type.

```
error[E0106]: missing lifetime specifier
  --> $DIR/variadic-ffi-6.rs:7:6
   |
LL | ) -> &usize {
   |      ^ expected named lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
   |
LL | ) -> &'static usize {
   |       +++++++
help: instead, you are more likely to want to change one of the arguments to be borrowed...
   |
LL |     x: &usize,
   |        +
help: ...or alternatively, to want to return an owned value
   |
LL - ) -> &usize {
LL + ) -> usize {
   |
```

Fix rust-lang#85843.
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@wesleywiser wesleywiser wesleywiser approved these changes

Assignees

@wesleywiser wesleywiser

Labels

A-testsuite Area: The testsuite used to check the correctness of rustc S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

Projects

None yet

Milestone

1.76.0

Development

Successfully merging this pull request may close these issues.

Suggest borrowing from argument when return type is a borrow without an applicable lifetime

5 participants

@estebank @rustbot @rust-log-analyzer @bors @wesleywiser