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make const_generics_defaults use the unstable syntax mechanism

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This is important to not accidentally stabilize the parsing of the syntax while it still is experimental and not formally accepted
This commit is contained in:
Rémy Rakic 2020-12-31 18:32:06 +01:00
parent 1fc3c4c16d
commit 942b7ce2c1
9 changed files with 45 additions and 35 deletions
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17
compiler/rustc_parse/src/parser/generics.rs
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@ -5,7 +5,7 @@ use rustc_ast::{
self as ast, Attribute, GenericBounds, GenericParam, GenericParamKind, WhereClause,
};
use rustc_errors::PResult;
use rustc_span::symbol::kw;
use rustc_span::symbol::{kw, sym};
impl<'a> Parser<'a> {
/// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
@ -56,8 +56,19 @@ impl<'a> Parser<'a> {
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
// Parse optional const generics default value.
let default = if self.eat(&token::Eq) { Some(self.parse_const_arg()?) } else { None };
// Parse optional const generics default value, taking care of feature gating the spans
// with the unstable syntax mechanism.
let default = if self.eat(&token::Eq) {
// The gated span goes from the `=` to the end of the const argument that follows (and
// which could be a block expression).
let start = self.prev_token.span;
let const_arg = self.parse_const_arg()?;
let span = start.to(const_arg.value.span);
self.sess.gated_spans.gate(sym::const_generics_defaults, span);
Some(const_arg)
} else {
None
};
Ok(GenericParam {
ident,