rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Introduce const Trait (always-const trait bounds)

Browse Source
This commit is contained in:
León Orell Valerian Liehr
2023-12-18 17:55:55 +01:00
parent 2fe50cd72c
commit 3eb48a35c8
69 changed files with 505 additions and 223 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
compiler/rustc_parse/src/parser/ty.rs
View File

@@ -86,6 +86,18 @@ fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
t == &token::ModSep || t == &token::Lt || t == &token::BinOp(token::Shl)
}
fn can_begin_dyn_bound_in_edition_2015(t: &Token) -> bool {
// `Not`, `Tilde` & `Const` are deliberately not part of this list to
// contain the number of potential regressions esp. in MBE code.
// `Const` would regress `rfc-2632-const-trait-impl/mbe-dyn-const-2015.rs`.
// `Not` would regress `dyn!(...)` macro calls in Rust 2015.
t.is_path_start()
|| t.is_lifetime()
|| t == &TokenKind::Question
|| t.is_keyword(kw::For)
|| t == &TokenKind::OpenDelim(Delimiter::Parenthesis)
}
impl<'a> Parser<'a> {
/// Parses a type.
pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
@@ -665,7 +677,8 @@ impl<'a> Parser<'a> {
self.check_keyword(kw::Dyn)
&& (self.token.uninterpolated_span().at_least_rust_2018()
|| self.look_ahead(1, |t| {
(t.can_begin_bound() || t.kind == TokenKind::BinOp(token::Star))
(can_begin_dyn_bound_in_edition_2015(t)
|| t.kind == TokenKind::BinOp(token::Star))
&& !can_continue_type_after_non_fn_ident(t)
}))
}
@@ -758,12 +771,12 @@ impl<'a> Parser<'a> {
/// Can the current token begin a bound?
fn can_begin_bound(&mut self) -> bool {
// This needs to be synchronized with `TokenKind::can_begin_bound`.
self.check_path()
|| self.check_lifetime()
|| self.check(&token::Not)
|| self.check(&token::Question)
|| self.check(&token::Tilde)
|| self.check_keyword(kw::Const)
|| self.check_keyword(kw::For)
|| self.check(&token::OpenDelim(Delimiter::Parenthesis))
}
@@ -812,8 +825,11 @@ impl<'a> Parser<'a> {
fn error_lt_bound_with_modifiers(&self, modifiers: TraitBoundModifiers) {
match modifiers.constness {
BoundConstness::Never => {}
BoundConstness::Maybe(span) => {
self.dcx().emit_err(errors::TildeConstLifetime { span });
BoundConstness::Always(span) | BoundConstness::Maybe(span) => {
self.dcx().emit_err(errors::ModifierLifetime {
span,
modifier: modifiers.constness.as_str(),
});
}
}
@@ -822,7 +838,7 @@ impl<'a> Parser<'a> {
BoundPolarity::Negative(span) | BoundPolarity::Maybe(span) => {
self.dcx().emit_err(errors::ModifierLifetime {
span,
sigil: modifiers.polarity.as_str(),
modifier: modifiers.polarity.as_str(),
});
}
}
@@ -848,7 +864,7 @@ impl<'a> Parser<'a> {
/// If no modifiers are present, this does not consume any tokens.
///
/// ```ebnf
/// TRAIT_BOUND_MODIFIERS = ["~const"] ["?" | "!"]
/// TRAIT_BOUND_MODIFIERS = [["~"] "const"] ["?" | "!"]
/// ```
fn parse_trait_bound_modifiers(&mut self) -> PResult<'a, TraitBoundModifiers> {
let constness = if self.eat(&token::Tilde) {
@@ -858,11 +874,8 @@ impl<'a> Parser<'a> {
self.sess.gated_spans.gate(sym::const_trait_impl, span);
BoundConstness::Maybe(span)
} else if self.eat_keyword(kw::Const) {
let span = self.prev_token.span;
self.sess.gated_spans.gate(sym::const_trait_impl, span);
self.dcx().emit_err(errors::ConstMissingTilde { span, start: span.shrink_to_lo() });
BoundConstness::Maybe(span)
self.sess.gated_spans.gate(sym::const_trait_impl, self.prev_token.span);
BoundConstness::Always(self.prev_token.span)
} else {
BoundConstness::Never
};