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Fix format string grammar in docs and improve alignment error message

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This commit is contained in:
Nilotpal Gupta 2025-08-19 11:10:32 +05:30
parent 269d5b56bc
commit fdbaaac245
4 changed files with 19 additions and 9 deletions
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4
compiler/rustc_parse_format/src/lib.rs
View file

@ -858,7 +858,9 @@ impl<'input> Parser<'input> {
self.errors.insert(
0,
ParseError {
description: "expected format parameter to occur after `:`".to_owned(),
description:
"expected alignment specifier after `:` in format string; example: `{:>?}`"
.to_owned(),
note: None,
label: format!("expected `{}` to occur after `:`", alignment),
span: range,

2
library/alloc/src/fmt.rs
View file

@ -354,7 +354,7 @@
//! sign := '+' | '-'
//! width := count
//! precision := count | '*'
//! type := '?' | 'x?' | 'X?' | identifier
//! type := '?' | 'x?' | 'X?' | 'o' | 'x' | 'X' | 'p' | 'b' | 'e' | 'E'
//! count := parameter | integer
//! parameter := argument '$'
//! ```

8
tests/ui/fmt/format-string-wrong-order.rs
View file

@ -13,9 +13,11 @@ fn main() {
format!("{?:#?}", bar);
//~^ ERROR invalid format string: expected format parameter to occur after `:`
format!("Hello {<5:}!", "x");
//~^ ERROR invalid format string: expected format parameter to occur after `:`
//~^ ERROR invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
format!("Hello {^5:}!", "x");
//~^ ERROR invalid format string: expected format parameter to occur after `:`
//~^ ERROR invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
format!("Hello {>5:}!", "x");
//~^ ERROR invalid format string: expected format parameter to occur after `:`
//~^ ERROR invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
println!("{0:#X>18}", 12345);
//~^ ERROR invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
}

14
tests/ui/fmt/format-string-wrong-order.stderr
View file

@ -50,23 +50,29 @@ LL | format!("{?:#?}", bar);
|
= note: `?` comes after `:`, try `:?` instead
error: invalid format string: expected format parameter to occur after `:`
error: invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
--> $DIR/format-string-wrong-order.rs:15:21
|
LL | format!("Hello {<5:}!", "x");
| ^ expected `<` to occur after `:` in format string
error: invalid format string: expected format parameter to occur after `:`
error: invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
--> $DIR/format-string-wrong-order.rs:17:21
|
LL | format!("Hello {^5:}!", "x");
| ^ expected `^` to occur after `:` in format string
error: invalid format string: expected format parameter to occur after `:`
error: invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
--> $DIR/format-string-wrong-order.rs:19:21
|
LL | format!("Hello {>5:}!", "x");
| ^ expected `>` to occur after `:` in format string
error: aborting due to 9 previous errors
error: invalid format string: expected alignment specifier after `:` in format string; example: `{:>?}`
--> $DIR/format-string-wrong-order.rs:21:20
|
LL | println!("{0:#X>18}", 12345);
| ^ expected `>` to occur after `:` in format string
error: aborting due to 10 previous errors