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Phrase flag in terms of whether core::fmt machinery is required

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David Tolnay 2024-02-11 10:27:02 -08:00
parent d43b759e3a
commit f790bee2a4
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GPG key ID: F9BA143B95FF6D82
2 changed files with 8 additions and 10 deletions
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12
impl/src/attr.rs
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@ -18,9 +18,9 @@ pub struct Attrs<'a> {
#[derive(Clone)] #[derive(Clone)]
pub struct Display<'a> { pub struct Display<'a> {
pub original: &'a Attribute, pub original: &'a Attribute,
pub use_write_str: bool,
pub fmt: LitStr, pub fmt: LitStr,
pub args: TokenStream, pub args: TokenStream,
pub requires_fmt_machinery: bool,
pub has_bonus_display: bool, pub has_bonus_display: bool,
pub implied_bounds: Set<(usize, Trait)>, pub implied_bounds: Set<(usize, Trait)>,
} }
@ -106,12 +106,12 @@ fn parse_error_attribute<'a>(attrs: &mut Attrs<'a>, attr: &'a Attribute) -> Resu
let fmt: LitStr = input.parse()?; let fmt: LitStr = input.parse()?;
let args = parse_token_expr(input, false)?; let args = parse_token_expr(input, false)?;
let requires_fmt_machinery = !args.is_empty();
let display = Display { let display = Display {
original: attr, original: attr,
// This will be updated later if format_args are still required (i.e. has braces)
use_write_str: args.is_empty(),
fmt, fmt,
args, args,
requires_fmt_machinery,
has_bonus_display: false, has_bonus_display: false,
implied_bounds: Set::new(), implied_bounds: Set::new(),
}; };
@ -205,13 +205,13 @@ impl ToTokens for Display<'_> {
// Currently `write!(f, "text")` produces less efficient code than // Currently `write!(f, "text")` produces less efficient code than
// `f.write_str("text")`. We recognize the case when the format string // `f.write_str("text")`. We recognize the case when the format string
// has no braces and no interpolated values, and generate simpler code. // has no braces and no interpolated values, and generate simpler code.
tokens.extend(if self.use_write_str { tokens.extend(if self.requires_fmt_machinery {
quote! { quote! {
__formatter.write_str(#fmt) ::core::write!(__formatter, #fmt #args)
} }
} else { } else {
quote! { quote! {
::core::write!(__formatter, #fmt #args) __formatter.write_str(#fmt)
} }
}); });
} }

6
impl/src/fmt.rs
View file

@ -32,12 +32,10 @@ impl Display<'_> {
} }
} }
if self.use_write_str && fmt.contains('}') { self.requires_fmt_machinery = self.requires_fmt_machinery || fmt.contains('}');
self.use_write_str = false;
}
while let Some(brace) = read.find('{') { while let Some(brace) = read.find('{') {
self.use_write_str = false; self.requires_fmt_machinery = true;
out += &read[..brace + 1]; out += &read[..brace + 1];
read = &read[brace + 1..]; read = &read[brace + 1..];
if read.starts_with('{') { if read.starts_with('{') {