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Rollup merge of rust-lang#89922 - JohnTitor:update-e0637, r=jackh726
Update E0637 description to mention `&` w/o an explicit lifetime name Deal with rust-lang#89824 (comment). Another solution would be splitting the error code into two as (I think) it's a bit unclear to users why they have the same error code.
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@@ -1,35 +1,51 @@ | ||
An underscore `_` character has been used as the identifier for a lifetime. | ||
`'_` lifetime name or `&T` without an explicit lifetime name has been used | ||
on illegal place. | ||
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Erroneous code example: | ||
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```compile_fail,E0106,E0637 | ||
fn longest<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ||
//^^ `'_` is a reserved lifetime name | ||
fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ||
//^^ `'_` is a reserved lifetime name | ||
if str1.len() > str2.len() { | ||
str1 | ||
} else { | ||
str2 | ||
} | ||
} | ||
fn and_without_explicit_lifetime<T>() | ||
where | ||
T: Into<&u32>, | ||
//^ `&` without an explicit lifetime name | ||
{ | ||
} | ||
``` | ||
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`'_`, cannot be used as a lifetime identifier because it is a reserved for the | ||
anonymous lifetime. To fix this, use a lowercase letter such as 'a, or a series | ||
of lowercase letters such as `'foo`. For more information, see [the | ||
book][bk-no]. For more information on using the anonymous lifetime in rust | ||
nightly, see [the nightly book][bk-al]. | ||
First, `'_` cannot be used as a lifetime identifier in some places | ||
because it is a reserved for the anonymous lifetime. Second, `&T` | ||
without an explicit lifetime name cannot also be used in some places. | ||
To fix them, use a lowercase letter such as `'a`, or a series | ||
of lowercase letters such as `'foo`. For more information about lifetime | ||
identifier, see [the book][bk-no]. For more information on using | ||
the anonymous lifetime in Rust 2018, see [the Rust 2018 blog post][blog-al]. | ||
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Corrected example: | ||
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``` | ||
fn longest<'a>(str1: &'a str, str2: &'a str) -> &'a str { | ||
fn underscore_lifetime<'a>(str1: &'a str, str2: &'a str) -> &'a str { | ||
if str1.len() > str2.len() { | ||
str1 | ||
} else { | ||
str2 | ||
} | ||
} | ||
fn and_without_explicit_lifetime<'foo, T>() | ||
where | ||
T: Into<&'foo u32>, | ||
{ | ||
} | ||
``` | ||
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[bk-no]: https://doc.rust-lang.org/book/appendix-02-operators.html#non-operator-symbols | ||
[bk-al]: https://doc.rust-lang.org/nightly/edition-guide/rust-2018/ownership-and-lifetimes/the-anonymous-lifetime.html | ||
[blog-al]: https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html#more-lifetime-elision-rules |
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@@ -1,9 +1,17 @@ | ||
struct Foo<'a: '_>(&'a u8); //~ ERROR cannot be used here | ||
fn foo<'a: '_>(_: &'a u8) {} //~ ERROR cannot be used here | ||
fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ||
//~^ ERROR: `'_` cannot be used here [E0637] | ||
//~| ERROR: missing lifetime specifier | ||
if str1.len() > str2.len() { | ||
str1 | ||
} else { | ||
str2 | ||
} | ||
} | ||
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struct Bar<'a>(&'a u8); | ||
impl<'a: '_> Bar<'a> { //~ ERROR cannot be used here | ||
fn bar() {} | ||
fn and_without_explicit_lifetime<T>() | ||
where | ||
T: Into<&u32>, //~ ERROR: `&` without an explicit lifetime name cannot be used here [E0637] | ||
{ | ||
} | ||
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fn main() {} |
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@@ -1,21 +1,28 @@ | ||
error[E0637]: `'_` cannot be used here | ||
--> $DIR/E0637.rs:1:16 | ||
--> $DIR/E0637.rs:1:24 | ||
| | ||
LL | struct Foo<'a: '_>(&'a u8); | ||
| ^^ `'_` is a reserved lifetime name | ||
LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ||
| ^^ `'_` is a reserved lifetime name | ||
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error[E0637]: `'_` cannot be used here | ||
--> $DIR/E0637.rs:2:12 | ||
error[E0637]: `&` without an explicit lifetime name cannot be used here | ||
--> $DIR/E0637.rs:13:13 | ||
| | ||
LL | fn foo<'a: '_>(_: &'a u8) {} | ||
| ^^ `'_` is a reserved lifetime name | ||
LL | T: Into<&u32>, | ||
| ^ explicit lifetime name needed here | ||
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error[E0637]: `'_` cannot be used here | ||
--> $DIR/E0637.rs:5:10 | ||
error[E0106]: missing lifetime specifier | ||
--> $DIR/E0637.rs:1:62 | ||
| | ||
LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ||
| ------- ------- ^^ expected named lifetime parameter | ||
| | ||
= help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `str1` or `str2` | ||
help: consider introducing a named lifetime parameter | ||
| | ||
LL | impl<'a: '_> Bar<'a> { | ||
| ^^ `'_` is a reserved lifetime name | ||
LL | fn underscore_lifetime<'a, '_>(str1: &'a str, str2: &'a str) -> &'a 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 E0637`. | ||
Some errors have detailed explanations: E0106, E0637. | ||
For more information about an error, try `rustc --explain E0106`. |