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Optimize escape_string_symbol() #159609

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rust-bors merged 1 commit into from
Jul 22, 2026
+16 −1
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Optimize escape_string_symbol() #159609

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17 changes: 16 additions & 1 deletion compiler/rustc_ast/src/util/literal.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
//! Code related to parsing literals.

use std::fmt::Write as _;
use std::{ascii, fmt, str};

use rustc_literal_escaper::{
Expand All @@ -14,8 +15,22 @@ use crate::token::{self, Token};
// Escapes a string, represented as a symbol. Reuses the original symbol,
// avoiding interning, if no changes are required.
pub fn escape_string_symbol(symbol: Symbol) -> Symbol {
// Don't use escape_default() here, because using it in conjunction with to_string()
// is slow.
let s = symbol.as_str();
let escaped = s.escape_default().to_string();
let mut escaped = String::with_capacity(s.len());
for c in s.chars() {
match c {
'\t' => escaped.push_str("\\t"),
'\r' => escaped.push_str("\\r"),
'\n' => escaped.push_str("\\n"),
'\\' => escaped.push_str("\\\\"),
'\'' => escaped.push_str("\\'"),
'\"' => escaped.push_str("\\\""),
'\x20'..='\x7e' => escaped.push(c),
c => write!(escaped, "\\u{{{:x}}}", c as u32).unwrap(),
}
}
if s == escaped { symbol } else { Symbol::intern(&escaped) }
}

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