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Suggest borrowing arguments in generic positions when trait bounds ar…
…e satisfied This subsumes the suggestions to borrow arguments with `AsRef`/`Borrow` bounds and those to borrow arguments with `Fn` and `FnMut` bounds. It works for other traits implemented on references as well, such as `std::io::Read`, `std::io::Write`, and `core::fmt::Write`. Incidentally, by making the logic for suggesting borrowing closures general, this removes some spurious suggestions to mutably borrow `FnMut` closures in assignments, as well as an unhelpful suggestion to add a `Clone` constraint to an `impl Fn` argument.
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316 changes: 157 additions & 159 deletions
316
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
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27 changes: 12 additions & 15 deletions
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tests/ui/moves/auxiliary/suggest-borrow-for-generic-arg-aux.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,23 +1,20 @@ | ||
| //! auxiliary definitons for suggest-borrow-for-generic-arg.rs, to ensure the suggestion works on | ||
| //! functions defined in other crates. | ||
| use std::borrow::{Borrow, BorrowMut}; | ||
| use std::convert::{AsMut, AsRef}; | ||
| pub struct Bar; | ||
| use std::io::{self, Read, Write}; | ||
| use std::iter::Sum; | ||
|
|
||
| impl AsRef<Bar> for Bar { | ||
| fn as_ref(&self) -> &Bar { | ||
| self | ||
| } | ||
| pub fn write_stuff<W: Write>(mut writer: W) -> io::Result<()> { | ||
| writeln!(writer, "stuff") | ||
| } | ||
|
|
||
| impl AsMut<Bar> for Bar { | ||
| fn as_mut(&mut self) -> &mut Bar { | ||
| self | ||
| } | ||
| pub fn read_and_discard<R: Read>(mut reader: R) -> io::Result<()> { | ||
| let mut buf = Vec::new(); | ||
| reader.read_to_end(&mut buf).map(|_| ()) | ||
| } | ||
|
|
||
| pub fn foo<T: AsRef<Bar>>(_: T) {} | ||
| pub fn qux<T: AsMut<Bar>>(_: T) {} | ||
| pub fn bat<T: Borrow<T>>(_: T) {} | ||
| pub fn baz<T: BorrowMut<T>>(_: T) {} | ||
| pub fn sum_three<I: IntoIterator>(iter: I) -> <I as IntoIterator>::Item | ||
| where <I as IntoIterator>::Item: Sum | ||
| { | ||
| iter.into_iter().take(3).sum() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,22 +1,46 @@ | ||
| //! Test suggetions to borrow generic arguments instead of moving when all predicates hold after | ||
| //! substituting in the reference type. | ||
| //! Test suggetions to borrow generic arguments instead of moving. Tests for other instances of this | ||
| //! can be found in `moved-value-on-as-ref-arg.rs` and `borrow-closures-instead-of-move.rs` | ||
| //@ run-rustfix | ||
| //@ aux-build:suggest-borrow-for-generic-arg-aux.rs | ||
| //@ aux-crate:aux=suggest-borrow-for-generic-arg-aux.rs | ||
| //@ edition: 2021 | ||
|
|
||
| #![allow(unused_mut)] | ||
| extern crate suggest_borrow_for_generic_arg_aux as aux; | ||
| use std::io::{self, Write}; | ||
|
|
||
| pub fn main() { | ||
| let bar = aux::Bar; | ||
| aux::foo(&bar); //~ HELP consider borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| let mut bar = aux::Bar; | ||
| aux::qux(&mut bar); //~ HELP consider mutably borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| let bar = aux::Bar; | ||
| aux::bat(&bar); //~ HELP consider borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| let mut bar = aux::Bar; | ||
| aux::baz(&mut bar); //~ HELP consider mutably borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| // test for `std::io::Write` (#131413) | ||
| fn test_write() -> io::Result<()> { | ||
| let mut stdout = io::stdout(); | ||
| aux::write_stuff(&stdout)?; //~ HELP consider borrowing `stdout` | ||
| writeln!(stdout, "second line")?; //~ ERROR borrow of moved value: `stdout` | ||
|
|
||
| let mut buf = Vec::new(); | ||
| aux::write_stuff(&mut buf.clone())?; //~ HELP consider mutably borrowing `buf` | ||
| //~^ HELP consider cloning the value | ||
| writeln!(buf, "second_line") //~ ERROR borrow of moved value: `buf` | ||
| } | ||
|
|
||
| /// test for `std::io::Read` (#131413) | ||
| fn test_read() -> io::Result<()> { | ||
| let stdin = io::stdin(); | ||
| aux::read_and_discard(&stdin)?; //~ HELP consider borrowing `stdin` | ||
| aux::read_and_discard(stdin)?; //~ ERROR use of moved value: `stdin` | ||
|
|
||
| let mut bytes = std::collections::VecDeque::from([1, 2, 3, 4, 5, 6]); | ||
| aux::read_and_discard(&mut bytes.clone())?; //~ HELP consider mutably borrowing `bytes` | ||
| //~^ HELP consider cloning the value | ||
| aux::read_and_discard(bytes) //~ ERROR use of moved value: `bytes` | ||
| } | ||
|
|
||
| /// test that suggestions work with projection types in the callee's signature | ||
| fn test_projections() { | ||
| let mut iter = [1, 2, 3, 4, 5, 6].into_iter(); | ||
| let _six: usize = aux::sum_three(&mut iter.clone()); //~ HELP consider mutably borrowing `iter` | ||
| //~^ HELP consider cloning the value | ||
| let _fifteen: usize = aux::sum_three(iter); //~ ERROR use of moved value: `iter` | ||
| } | ||
|
|
||
| fn main() { | ||
| test_write().unwrap(); | ||
| test_read().unwrap(); | ||
| test_projections(); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,22 +1,46 @@ | ||
| //! Test suggetions to borrow generic arguments instead of moving when all predicates hold after | ||
| //! substituting in the reference type. | ||
| //! Test suggetions to borrow generic arguments instead of moving. Tests for other instances of this | ||
| //! can be found in `moved-value-on-as-ref-arg.rs` and `borrow-closures-instead-of-move.rs` | ||
| //@ run-rustfix | ||
| //@ aux-build:suggest-borrow-for-generic-arg-aux.rs | ||
| //@ aux-crate:aux=suggest-borrow-for-generic-arg-aux.rs | ||
| //@ edition: 2021 | ||
|
|
||
| #![allow(unused_mut)] | ||
| extern crate suggest_borrow_for_generic_arg_aux as aux; | ||
| use std::io::{self, Write}; | ||
|
|
||
| pub fn main() { | ||
| let bar = aux::Bar; | ||
| aux::foo(bar); //~ HELP consider borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| let mut bar = aux::Bar; | ||
| aux::qux(bar); //~ HELP consider mutably borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| let bar = aux::Bar; | ||
| aux::bat(bar); //~ HELP consider borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| let mut bar = aux::Bar; | ||
| aux::baz(bar); //~ HELP consider mutably borrowing `bar` | ||
| let _baa = bar; //~ ERROR use of moved value | ||
| // test for `std::io::Write` (#131413) | ||
| fn test_write() -> io::Result<()> { | ||
| let mut stdout = io::stdout(); | ||
| aux::write_stuff(stdout)?; //~ HELP consider borrowing `stdout` | ||
| writeln!(stdout, "second line")?; //~ ERROR borrow of moved value: `stdout` | ||
|
|
||
| let mut buf = Vec::new(); | ||
| aux::write_stuff(buf)?; //~ HELP consider mutably borrowing `buf` | ||
| //~^ HELP consider cloning the value | ||
| writeln!(buf, "second_line") //~ ERROR borrow of moved value: `buf` | ||
| } | ||
|
|
||
| /// test for `std::io::Read` (#131413) | ||
| fn test_read() -> io::Result<()> { | ||
| let stdin = io::stdin(); | ||
| aux::read_and_discard(stdin)?; //~ HELP consider borrowing `stdin` | ||
| aux::read_and_discard(stdin)?; //~ ERROR use of moved value: `stdin` | ||
|
|
||
| let mut bytes = std::collections::VecDeque::from([1, 2, 3, 4, 5, 6]); | ||
| aux::read_and_discard(bytes)?; //~ HELP consider mutably borrowing `bytes` | ||
| //~^ HELP consider cloning the value | ||
| aux::read_and_discard(bytes) //~ ERROR use of moved value: `bytes` | ||
| } | ||
|
|
||
| /// test that suggestions work with projection types in the callee's signature | ||
| fn test_projections() { | ||
| let mut iter = [1, 2, 3, 4, 5, 6].into_iter(); | ||
| let _six: usize = aux::sum_three(iter); //~ HELP consider mutably borrowing `iter` | ||
| //~^ HELP consider cloning the value | ||
| let _fifteen: usize = aux::sum_three(iter); //~ ERROR use of moved value: `iter` | ||
| } | ||
|
|
||
| fn main() { | ||
| test_write().unwrap(); | ||
| test_read().unwrap(); | ||
| test_projections(); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,63 +1,93 @@ | ||
| error[E0382]: use of moved value: `bar` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:12:16 | ||
| error[E0382]: borrow of moved value: `stdout` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:14:14 | ||
| | | ||
| LL | let bar = aux::Bar; | ||
| | --- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait | ||
| LL | aux::foo(bar); | ||
| | --- value moved here | ||
| LL | let _baa = bar; | ||
| | ^^^ value used here after move | ||
| LL | let mut stdout = io::stdout(); | ||
| | ---------- move occurs because `stdout` has type `Stdout`, which does not implement the `Copy` trait | ||
| LL | aux::write_stuff(stdout)?; | ||
| | ------ value moved here | ||
| LL | writeln!(stdout, "second line")?; | ||
| | ^^^^^^ value borrowed here after move | ||
| | | ||
| help: consider borrowing `bar` | ||
| help: consider borrowing `stdout` | ||
| | | ||
| LL | aux::foo(&bar); | ||
| | + | ||
| LL | aux::write_stuff(&stdout)?; | ||
| | + | ||
|
|
||
| error[E0382]: use of moved value: `bar` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:15:16 | ||
| error[E0382]: borrow of moved value: `buf` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:19:14 | ||
| | | ||
| LL | let mut bar = aux::Bar; | ||
| | ------- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait | ||
| LL | aux::qux(bar); | ||
| | --- value moved here | ||
| LL | let _baa = bar; | ||
| | ^^^ value used here after move | ||
| LL | let mut buf = Vec::new(); | ||
| | ------- move occurs because `buf` has type `Vec<u8>`, which does not implement the `Copy` trait | ||
| LL | aux::write_stuff(buf)?; | ||
| | --- value moved here | ||
| LL | | ||
| LL | writeln!(buf, "second_line") | ||
| | ^^^ value borrowed here after move | ||
| | | ||
| help: consider mutably borrowing `bar` | ||
| help: consider mutably borrowing `buf` | ||
| | | ||
| LL | aux::qux(&mut bar); | ||
| | ++++ | ||
| LL | aux::write_stuff(&mut buf)?; | ||
| | ++++ | ||
| help: consider cloning the value if the performance cost is acceptable | ||
| | | ||
| LL | aux::write_stuff(buf.clone())?; | ||
| | ++++++++ | ||
|
|
||
| error[E0382]: use of moved value: `bar` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:18:16 | ||
| error[E0382]: use of moved value: `stdin` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:26:27 | ||
| | | ||
| LL | let bar = aux::Bar; | ||
| | --- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait | ||
| LL | aux::bat(bar); | ||
| | --- value moved here | ||
| LL | let _baa = bar; | ||
| | ^^^ value used here after move | ||
| LL | let stdin = io::stdin(); | ||
| | ----- move occurs because `stdin` has type `Stdin`, which does not implement the `Copy` trait | ||
| LL | aux::read_and_discard(stdin)?; | ||
| | ----- value moved here | ||
| LL | aux::read_and_discard(stdin)?; | ||
| | ^^^^^ value used here after move | ||
| | | ||
| help: consider borrowing `bar` | ||
| help: consider borrowing `stdin` | ||
| | | ||
| LL | aux::bat(&bar); | ||
| | + | ||
| LL | aux::read_and_discard(&stdin)?; | ||
| | + | ||
|
|
||
| error[E0382]: use of moved value: `bar` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:21:16 | ||
| error[E0382]: use of moved value: `bytes` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:31:27 | ||
| | | ||
| LL | let mut bytes = std::collections::VecDeque::from([1, 2, 3, 4, 5, 6]); | ||
| | --------- move occurs because `bytes` has type `VecDeque<u8>`, which does not implement the `Copy` trait | ||
| LL | aux::read_and_discard(bytes)?; | ||
| | ----- value moved here | ||
| LL | | ||
| LL | aux::read_and_discard(bytes) | ||
| | ^^^^^ value used here after move | ||
| | | ||
| help: consider mutably borrowing `bytes` | ||
| | | ||
| LL | aux::read_and_discard(&mut bytes)?; | ||
| | ++++ | ||
| help: consider cloning the value if the performance cost is acceptable | ||
| | | ||
| LL | aux::read_and_discard(bytes.clone())?; | ||
| | ++++++++ | ||
|
|
||
| error[E0382]: use of moved value: `iter` | ||
| --> $DIR/suggest-borrow-for-generic-arg.rs:39:42 | ||
| | | ||
| LL | let mut iter = [1, 2, 3, 4, 5, 6].into_iter(); | ||
| | -------- move occurs because `iter` has type `std::array::IntoIter<usize, 6>`, which does not implement the `Copy` trait | ||
| LL | let _six: usize = aux::sum_three(iter); | ||
| | ---- value moved here | ||
| LL | | ||
| LL | let _fifteen: usize = aux::sum_three(iter); | ||
| | ^^^^ value used here after move | ||
| | | ||
| LL | let mut bar = aux::Bar; | ||
| | ------- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait | ||
| LL | aux::baz(bar); | ||
| | --- value moved here | ||
| LL | let _baa = bar; | ||
| | ^^^ value used here after move | ||
| help: consider mutably borrowing `iter` | ||
| | | ||
| help: consider mutably borrowing `bar` | ||
| LL | let _six: usize = aux::sum_three(&mut iter); | ||
| | ++++ | ||
| help: consider cloning the value if the performance cost is acceptable | ||
| | | ||
| LL | aux::baz(&mut bar); | ||
| | ++++ | ||
| LL | let _six: usize = aux::sum_three(iter.clone()); | ||
| | ++++++++ | ||
|
|
||
| error: aborting due to 4 previous errors | ||
| error: aborting due to 5 previous errors | ||
|
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||
| For more information about this error, try `rustc --explain E0382`. |
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