bjoernager/rust
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Stabilize format_args_capture

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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
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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();
}