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rustc_span: Provide a reserved identifier check for a specific edition #80272

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rustc_span: Provide a reserved identifier check for a specific edition
Edition evaluation is kept lazy because it may be expensive.
petrochenkov committed Dec 21, 2020
commit 00ff7fe6bd068b457fcd70de943d4ed81d58e1a5
43 changes: 32 additions & 11 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
@@ -13,7 +13,7 @@ use std::fmt;
use std::hash::{Hash, Hasher};
use std::str;

use crate::{Span, DUMMY_SP, SESSION_GLOBALS};
use crate::{Edition, Span, DUMMY_SP, SESSION_GLOBALS};

#[cfg(test)]
mod tests;
@@ -1609,12 +1609,32 @@ pub mod sym {
}

impl Symbol {
fn is_used_keyword_2018(self) -> bool {
self >= kw::Async && self <= kw::Dyn
fn is_special(self) -> bool {
self <= kw::Underscore
}

fn is_unused_keyword_2018(self) -> bool {
self == kw::Try
fn is_used_keyword_always(self) -> bool {
self >= kw::As && self <= kw::While
}

fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
(self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
}

fn is_unused_keyword_always(self) -> bool {
self >= kw::Abstract && self <= kw::Yield
}

fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
self == kw::Try && edition() >= Edition::Edition2018
}

pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
self.is_special()
|| self.is_used_keyword_always()
|| self.is_unused_keyword_always()
|| self.is_used_keyword_conditional(edition)
|| self.is_unused_keyword_conditional(edition)
}

/// A keyword or reserved identifier that can be used as a path segment.
@@ -1642,26 +1662,27 @@ impl Ident {
// Returns `true` for reserved identifiers used internally for elided lifetimes,
// unnamed method parameters, crate root module, error recovery etc.
pub fn is_special(self) -> bool {
self.name <= kw::Underscore
self.name.is_special()
}

/// Returns `true` if the token is a keyword used in the language.
pub fn is_used_keyword(self) -> bool {
// Note: `span.edition()` is relatively expensive, don't call it unless necessary.
self.name >= kw::As && self.name <= kw::While
|| self.name.is_used_keyword_2018() && self.span.rust_2018()
self.name.is_used_keyword_always()
|| self.name.is_used_keyword_conditional(|| self.span.edition())
}

/// Returns `true` if the token is a keyword reserved for possible future use.
pub fn is_unused_keyword(self) -> bool {
// Note: `span.edition()` is relatively expensive, don't call it unless necessary.
self.name >= kw::Abstract && self.name <= kw::Yield
|| self.name.is_unused_keyword_2018() && self.span.rust_2018()
self.name.is_unused_keyword_always()
|| self.name.is_unused_keyword_conditional(|| self.span.edition())
}

/// Returns `true` if the token is either a special identifier or a keyword.
pub fn is_reserved(self) -> bool {
self.is_special() || self.is_used_keyword() || self.is_unused_keyword()
// Note: `span.edition()` is relatively expensive, don't call it unless necessary.
self.name.is_reserved(|| self.span.edition())
}

/// A keyword or reserved identifier that can be used as a path segment.