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Auto merge of #77502 - varkor:const-generics-suggest-enclosing-braces, r=petrochenkov

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Suggest that expressions that look like const generic arguments should be enclosed in brackets

I pulled out the changes for const expressions from https://github.com/rust-lang/rust/pull/71592 (without the trait object diagnostic changes) and made some small changes; the implementation is `@estebank's.`

We're also going to want to make some changes separately to account for trait objects (they result in poor diagnostics, as is evident from one of the test cases here), such as an adaption of https://github.com/rust-lang/rust/pull/72273.

Fixes https://github.com/rust-lang/rust/issues/70753.

r? `@petrochenkov`
This commit is contained in:
bors 2020-10-27 09:25:54 +00:00
commit 20b1e05a8d
19 changed files with 782 additions and 35 deletions
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14
compiler/rustc_parse/src/parser/expr.rs
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@ -359,6 +359,18 @@ impl<'a> Parser<'a> {
/// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
// When parsing const expressions, stop parsing when encountering `>`.
(
Some(
AssocOp::ShiftRight
| AssocOp::Greater
| AssocOp::GreaterEqual
| AssocOp::AssignOp(token::BinOpToken::Shr),
),
_,
) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
return None;
}
(Some(op), _) => (op, self.token.span),
(None, Some((Ident { name: sym::and, span }, false))) => {
self.error_bad_logical_op("and", "&&", "conjunction");
@ -1715,7 +1727,7 @@ impl<'a> Parser<'a> {
let lo = self.prev_token.span;
let pat = self.parse_top_pat(GateOr::No)?;
self.expect(&token::Eq)?;
let expr = self.with_res(Restrictions::NO_STRUCT_LITERAL, |this| {
let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
})?;
let span = lo.to(expr.span);