nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2025-04-13 12:36:47 +00:00
Code Issues Packages Projects Releases Wiki Activity

Stabilize format_args_capture

Browse Source 
Works as expected, and there are widespread reports of success with it,
as well as interest in it.
This commit is contained in:
Josh Triplett 2021-11-01 16:18:36 +01:00
parent 89c3d84b75
commit 8c9bfaa5f3
18 changed files with 20 additions and 118 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
compiler/rustc_borrowck/src/lib.rs
View File

@ -3,7 +3,7 @@
#![feature(bool_to_option)]
#![feature(box_patterns)]
#![feature(crate_visibility_modifier)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(in_band_lifetimes)]
#![feature(iter_zip)]
#![feature(let_else)]

36
compiler/rustc_builtin_macros/src/format.rs
View File

@ -527,17 +527,9 @@ impl<'a, 'b> Context<'a, 'b> {
self.verify_arg_type(Exact(idx), ty)
}
None => {
let capture_feature_enabled = self
.ecx
.ecfg
.features
.map_or(false, |features| features.format_args_capture);
// For the moment capturing variables from format strings expanded from macros is
// disabled (see RFC #2795)
let can_capture = capture_feature_enabled && self.is_literal;
if can_capture {
if self.is_literal {
// Treat this name as a variable to capture from the surrounding scope
let idx = self.args.len();
self.arg_types.push(Vec::new());
@ -559,23 +551,15 @@ impl<'a, 'b> Context<'a, 'b> {
};
let mut err = self.ecx.struct_span_err(sp, &msg[..]);
if capture_feature_enabled && !self.is_literal {
err.note(&format!(
"did you intend to capture a variable `{}` from \
the surrounding scope?",
name
));
err.note(
"to avoid ambiguity, `format_args!` cannot capture variables \
when the format string is expanded from a macro",
);
} else if self.ecx.parse_sess().unstable_features.is_nightly_build() {
err.help(&format!(
"if you intended to capture `{}` from the surrounding scope, add \
`#![feature(format_args_capture)]` to the crate attributes",
name
));
}
err.note(&format!(
"did you intend to capture a variable `{}` from \
the surrounding scope?",
name
));
err.note(
"to avoid ambiguity, `format_args!` cannot capture variables \
when the format string is expanded from a macro",
);
err.emit();
}

2
compiler/rustc_errors/src/lib.rs
View File

@ -6,7 +6,7 @@
#![feature(crate_visibility_modifier)]
#![feature(backtrace)]
#![feature(if_let_guard)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(iter_zip)]
#![feature(let_else)]
#![feature(nll)]

2
compiler/rustc_expand/src/lib.rs
View File

@ -1,7 +1,7 @@
#![feature(crate_visibility_modifier)]
#![feature(decl_macro)]
#![feature(destructuring_assignment)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(if_let_guard)]
#![feature(iter_zip)]
#![feature(let_else)]

2
compiler/rustc_feature/src/accepted.rs
View File

@ -301,6 +301,8 @@ declare_features! (
(accepted, relaxed_struct_unsize, "1.58.0", Some(81793), None),
/// Allows dereferencing raw pointers during const eval.
(accepted, const_raw_ptr_deref, "1.58.0", Some(51911), None),
/// Allows capturing variables in scope using format_args!
(accepted, format_args_capture, "1.58.0", Some(67984), None),
// -------------------------------------------------------------------------
// feature-group-end: accepted features

3
compiler/rustc_feature/src/active.rs
View File

@ -539,9 +539,6 @@ declare_features! (
/// Be more precise when looking for live drops in a const context.
(active, const_precise_live_drops, "1.46.0", Some(73255), None),
/// Allows capturing variables in scope using format_args!
(active, format_args_capture, "1.46.0", Some(67984), None),
/// Allows `if let` guard in match arms.
(active, if_let_guard, "1.47.0", Some(51114), None),

2
compiler/rustc_lint/src/lib.rs
View File

@ -30,7 +30,7 @@
#![feature(bool_to_option)]
#![feature(box_patterns)]
#![feature(crate_visibility_modifier)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(iter_order_by)]
#![feature(iter_zip)]
#![feature(never_type)]

2
compiler/rustc_passes/src/lib.rs
View File

@ -7,7 +7,7 @@
#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
#![feature(crate_visibility_modifier)]
#![feature(in_band_lifetimes)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(iter_zip)]
#![feature(map_try_insert)]
#![feature(min_specialization)]

2
compiler/rustc_resolve/src/lib.rs
View File

@ -13,7 +13,7 @@
#![feature(drain_filter)]
#![feature(bool_to_option)]
#![feature(crate_visibility_modifier)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(iter_zip)]
#![feature(let_else)]
#![feature(never_type)]

2
compiler/rustc_typeck/src/lib.rs
View File

@ -58,7 +58,7 @@ This API is completely unstable and subject to change.
#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
#![feature(bool_to_option)]
#![feature(crate_visibility_modifier)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(if_let_guard)]
#![feature(in_band_lifetimes)]
#![feature(is_sorted)]

2
library/alloc/src/lib.rs
View File

@ -105,7 +105,7 @@
#![feature(fmt_internals)]
#![feature(fn_traits)]
#![feature(inherent_ascii_escape)]
#![feature(format_args_capture)]
#![cfg_attr(bootstrap, feature(format_args_capture))]
#![feature(inplace_iteration)]
#![feature(iter_advance_by)]
#![feature(iter_zip)]

47
src/doc/unstable-book/src/library-features/format-args-capture.md
View File

@ -1,47 +0,0 @@
# `format_args_capture`
The tracking issue for this feature is: [#67984]
[#67984]: https://github.com/rust-lang/rust/issues/67984
------------------------
Enables `format_args!` (and macros which use `format_args!` in their implementation, such
as `format!`, `print!` and `panic!`) to capture variables from the surrounding scope.
This avoids the need to pass named parameters when the binding in question
already exists in scope.
```rust
#![feature(format_args_capture)]
let (person, species, name) = ("Charlie Brown", "dog", "Snoopy");
// captures named argument `person`
print!("Hello {person}");
// captures named arguments `species` and `name`
format!("The {species}'s name is {name}.");
```
This also works for formatting parameters such as width and precision:
```rust
#![feature(format_args_capture)]
let precision = 2;
let s = format!("{:.precision$}", 1.324223);
assert_eq!(&s, "1.32");
```
A non-exhaustive list of macros which benefit from this functionality include:
- `format!`
- `print!` and `println!`
- `eprint!` and `eprintln!`
- `write!` and `writeln!`
- `panic!`
- `unreachable!`
- `unimplemented!`
- `todo!`
- `assert!` and similar
- macros in many thirdparty crates, such as `log`

6
src/test/ui/fmt/feature-gate-format-args-capture.rs
View File

@ -1,6 +0,0 @@
fn main() {
format!("{foo}"); //~ ERROR: there is no argument named `foo`
// panic! doesn't hit format_args! unless there are two or more arguments.
panic!("{foo} {bar}", bar=1); //~ ERROR: there is no argument named `foo`
}

18
src/test/ui/fmt/feature-gate-format-args-capture.stderr
View File

@ -1,18 +0,0 @@
error: there is no argument named `foo`
--> $DIR/feature-gate-format-args-capture.rs:2:14
|
LL | format!("{foo}");
| ^^^^^
|
= help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: there is no argument named `foo`
--> $DIR/feature-gate-format-args-capture.rs:5:13
|
LL | panic!("{foo} {bar}", bar=1);
| ^^^^^
|
= help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: aborting due to 2 previous errors

2
src/test/ui/fmt/format-args-capture-macro-hygiene.rs
View File

@ -1,5 +1,3 @@
#![feature(format_args_capture)]
fn main() {
format!(concat!("{foo}")); //~ ERROR: there is no argument named `foo`
format!(concat!("{ba", "r} {}"), 1); //~ ERROR: there is no argument named `bar`

2
src/test/ui/fmt/format-args-capture-missing-variables.rs
View File

@ -1,5 +1,3 @@
#![feature(format_args_capture)]
fn main() {
format!("{} {foo} {} {bar} {}", 1, 2, 3);
//~^ ERROR: cannot find value `foo` in this scope

1
src/test/ui/fmt/format-args-capture.rs
View File

@ -1,5 +1,4 @@
// run-pass
#![feature(format_args_capture)]
#![feature(cfg_panic)]
fn main() {

5
src/test/ui/fmt/ifmt-bad-arg.stderr
View File

@ -64,7 +64,6 @@ error: there is no argument named `foo`
LL | format!("{} {foo} {} {bar} {}", 1, 2, 3);
| ^^^^^
|
= help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: there is no argument named `bar`
--> $DIR/ifmt-bad-arg.rs:27:26
@ -72,7 +71,6 @@ error: there is no argument named `bar`
LL | format!("{} {foo} {} {bar} {}", 1, 2, 3);
| ^^^^^
|
= help: if you intended to capture `bar` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: there is no argument named `foo`
--> $DIR/ifmt-bad-arg.rs:31:14
@ -80,7 +78,6 @@ error: there is no argument named `foo`
LL | format!("{foo}");
| ^^^^^
|
= help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: multiple unused formatting arguments
--> $DIR/ifmt-bad-arg.rs:32:17
@ -162,7 +159,6 @@ error: there is no argument named `valueb`
LL | format!("{valuea} {valueb}", valuea=5, valuec=7);
| ^^^^^^^^
|
= help: if you intended to capture `valueb` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: named argument never used
--> $DIR/ifmt-bad-arg.rs:45:51
@ -214,7 +210,6 @@ error: there is no argument named `foo`
LL | {foo}
| ^^^^^
|
= help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
error: invalid format string: expected `'}'`, found `'t'`
--> $DIR/ifmt-bad-arg.rs:75:1