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Rework pattern and expression nonterminal kinds.

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Merge `PatParam`/`PatWithOr`, and `Expr`/`Expr2021`, for a few reasons.

- It's conceptually nice, because the two pattern kinds and the two
  expression kinds are very similar.

- With expressions in particular, there are several places where both
  expression kinds get the same treatment.

- It removes one unreachable match arm.

- Most importantly, for #124141 I will need to introduce a new type
  `MetaVarKind` that is very similar to `NonterminalKind`, but records a
  couple of extra fields for expression metavars. It's nicer to have a
  single `MetaVarKind::Expr` expression variant to hold those extra
  fields instead of duplicating them across two variants
  `MetaVarKind::{Expr,Expr2021}`. And then it makes sense for patterns
  to be treated the same way, and for `NonterminalKind` to also be
  treated the same way.

I also clarified the comments, because I have long found them a little
hard to understand.
This commit is contained in:
Nicholas Nethercote 2024-06-23 08:13:56 +10:00
parent 70fa67c0b2
commit e2aa38e6ab
5 changed files with 71 additions and 60 deletions
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28
compiler/rustc_parse/src/parser/nonterminal.rs
View file

@ -1,5 +1,7 @@
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, Nonterminal::*, NonterminalKind, Token};
use rustc_ast::token::{
self, Delimiter, Nonterminal::*, NonterminalKind, NtExprKind::*, NtPatKind::*, Token,
};
use rustc_ast::HasTokens;
use rustc_ast_pretty::pprust;
use rustc_data_structures::sync::Lrc;
@ -36,14 +38,14 @@ impl<'a> Parser<'a> {
}
match kind {
NonterminalKind::Expr2021 { inferred: _ } => {
NonterminalKind::Expr(Expr2021 { .. }) => {
token.can_begin_expr()
// This exception is here for backwards compatibility.
&& !token.is_keyword(kw::Let)
// This exception is here for backwards compatibility.
&& !token.is_keyword(kw::Const)
}
NonterminalKind::Expr => {
NonterminalKind::Expr(Expr) => {
token.can_begin_expr()
// This exception is here for backwards compatibility.
&& !token.is_keyword(kw::Let)
@ -74,7 +76,7 @@ impl<'a> Parser<'a> {
token::Interpolated(nt) => may_be_ident(nt),
_ => false,
},
NonterminalKind::PatParam { .. } | NonterminalKind::PatWithOr => match &token.kind {
NonterminalKind::Pat(pat_kind) => match &token.kind {
// box, ref, mut, and other identifiers (can stricten)
token::Ident(..) | token::NtIdent(..) |
token::OpenDelim(Delimiter::Parenthesis) | // tuple pattern
@ -89,7 +91,7 @@ impl<'a> Parser<'a> {
token::Lt | // path (UFCS constant)
token::BinOp(token::Shl) => true, // path (double UFCS)
// leading vert `|` or-pattern
token::BinOp(token::Or) => matches!(kind, NonterminalKind::PatWithOr),
token::BinOp(token::Or) => matches!(pat_kind, PatWithOr),
token::Interpolated(nt) => may_be_ident(nt),
_ => false,
},
@ -135,31 +137,25 @@ impl<'a> Parser<'a> {
.create_err(UnexpectedNonterminal::Statement(self.token.span)));
}
},
NonterminalKind::PatParam { .. } | NonterminalKind::PatWithOr => {
NtPat(self.collect_tokens_no_attrs(|this| match kind {
NonterminalKind::PatParam { .. } => this.parse_pat_no_top_alt(None, None),
NonterminalKind::PatWithOr => this.parse_pat_allow_top_alt(
NonterminalKind::Pat(pat_kind) => {
NtPat(self.collect_tokens_no_attrs(|this| match pat_kind {
PatParam { .. } => this.parse_pat_no_top_alt(None, None),
PatWithOr => this.parse_pat_allow_top_alt(
None,
RecoverComma::No,
RecoverColon::No,
CommaRecoveryMode::EitherTupleOrPipe,
),
_ => unreachable!(),
})?)
}
NonterminalKind::Expr | NonterminalKind::Expr2021 { inferred: _ } => {
NtExpr(self.parse_expr_force_collect()?)
}
NonterminalKind::Expr(_) => NtExpr(self.parse_expr_force_collect()?),
NonterminalKind::Literal => {
// The `:literal` matcher does not support attributes
NtLiteral(self.collect_tokens_no_attrs(|this| this.parse_literal_maybe_minus())?)
}
NonterminalKind::Ty => {
NtTy(self.collect_tokens_no_attrs(|this| this.parse_ty_no_question_mark_recover())?)
}
// this could be handled like a token, since it is one
NonterminalKind::Ident => {
return if let Some((ident, is_raw)) = get_macro_ident(&self.token) {