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Auto merge of #105805 - yanchen4791:issue-105227-fix, r=estebank
Suggest adding named lifetime when the return contains value borrowed from more than one lifetimes of function inputs fix for #105227. The problem: The suggestion of adding an explicit `'_` lifetime bound is **incorrect** when the function's return type contains a value which could be borrowed from more than one lifetimes of the function's inputs. Instead, a named lifetime parameter can be introduced in such a case. The solution: Checking the number of elided lifetimes in the function signature. If more than one lifetimes found in the function inputs when the suggestion of adding explicit `'_` lifetime, change it to using named lifetime parameter `'a` instead.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,26 @@ | ||
| // Regression test for issue #105227. | ||
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| // run-rustfix | ||
| #![allow(warnings)] | ||
| fn chars0<'a>(v :(&'a str, &'a str)) -> impl Iterator<Item = char> + 'a { | ||
| //~^ HELP to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a` | ||
| v.0.chars().chain(v.1.chars()) | ||
| //~^ ERROR hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds | ||
| } | ||
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| fn chars1<'a>(v0 : &'a str, v1 : &'a str) -> impl Iterator<Item = char> + 'a { | ||
| //~^ HELP to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a` | ||
| v0.chars().chain(v1.chars()) | ||
| //~^ ERROR hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bound | ||
| } | ||
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| fn chars2<'b>(v0 : &'b str, v1 : &'b str, v2 : &'b str) -> | ||
| //~^ HELP to declare that `impl Iterator<Item = char>` captures `'_`, you can use the named lifetime parameter `'b` | ||
| (impl Iterator<Item = char> + 'b , &'b str) | ||
| { | ||
| (v0.chars().chain(v1.chars()), v2) | ||
| //~^ ERROR hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bound | ||
| } | ||
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||
| fn main() { | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,26 @@ | ||
| // Regression test for issue #105227. | ||
|
|
||
| // run-rustfix | ||
| #![allow(warnings)] | ||
| fn chars0(v :(& str, &str)) -> impl Iterator<Item = char> { | ||
| //~^ HELP to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a` | ||
| v.0.chars().chain(v.1.chars()) | ||
| //~^ ERROR hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds | ||
| } | ||
|
|
||
| fn chars1(v0 : & str, v1 : &str) -> impl Iterator<Item = char> { | ||
| //~^ HELP to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a` | ||
| v0.chars().chain(v1.chars()) | ||
| //~^ ERROR hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bound | ||
| } | ||
|
|
||
| fn chars2<'b>(v0 : &str, v1 : &'_ str, v2 : &'b str) -> | ||
| //~^ HELP to declare that `impl Iterator<Item = char>` captures `'_`, you can use the named lifetime parameter `'b` | ||
| (impl Iterator<Item = char>, &'b str) | ||
| { | ||
| (v0.chars().chain(v1.chars()), v2) | ||
| //~^ ERROR hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bound | ||
| } | ||
|
|
||
| fn main() { | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| error[E0700]: hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds | ||
| --> $DIR/issue-105227.rs:7:5 | ||
| | | ||
| LL | fn chars0(v :(& str, &str)) -> impl Iterator<Item = char> { | ||
| | ----- hidden type `std::iter::Chain<Chars<'_>, Chars<'_>>` captures the anonymous lifetime defined here | ||
| LL | | ||
| LL | v.0.chars().chain(v.1.chars()) | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| help: to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a` | ||
| | | ||
| LL | fn chars0<'a>(v :(&'a str, &'a str)) -> impl Iterator<Item = char> + 'a { | ||
| | ++++ ++ ++ ++++ | ||
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| error[E0700]: hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds | ||
| --> $DIR/issue-105227.rs:13:5 | ||
| | | ||
| LL | fn chars1(v0 : & str, v1 : &str) -> impl Iterator<Item = char> { | ||
| | ----- hidden type `std::iter::Chain<Chars<'_>, Chars<'_>>` captures the anonymous lifetime defined here | ||
| LL | | ||
| LL | v0.chars().chain(v1.chars()) | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| help: to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a` | ||
| | | ||
| LL | fn chars1<'a>(v0 : &'a str, v1 : &'a str) -> impl Iterator<Item = char> + 'a { | ||
| | ++++ ++ ++ ++++ | ||
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| error[E0700]: hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds | ||
| --> $DIR/issue-105227.rs:21:5 | ||
| | | ||
| LL | fn chars2<'b>(v0 : &str, v1 : &'_ str, v2 : &'b str) -> | ||
| | ---- hidden type `std::iter::Chain<Chars<'_>, Chars<'_>>` captures the anonymous lifetime defined here | ||
| ... | ||
| LL | (v0.chars().chain(v1.chars()), v2) | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| help: to declare that `impl Iterator<Item = char>` captures `'_`, you can use the named lifetime parameter `'b` | ||
| | | ||
| LL ~ fn chars2<'b>(v0 : &'b str, v1 : &'b str, v2 : &'b str) -> | ||
| LL | | ||
| LL ~ (impl Iterator<Item = char> + 'b , &'b str) | ||
| | | ||
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| error: aborting due to 3 previous errors | ||
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| For more information about this error, try `rustc --explain E0700`. |