From e2aa38e6abf9c2ddd06fb2469628ee488dc49e30 Mon Sep 17 00:00:00 2001 From: Nicholas Nethercote Date: Sun, 23 Jun 2024 08:13:56 +1000 Subject: Rework pattern and expression nonterminal kinds. 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. --- compiler/rustc_ast/src/token.rs | 73 +++++++++++++++++++++++++---------------- 1 file changed, 44 insertions(+), 29 deletions(-) (limited to 'compiler/rustc_ast/src') diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs index cc66cc87652..efe19566152 100644 --- a/compiler/rustc_ast/src/token.rs +++ b/compiler/rustc_ast/src/token.rs @@ -1,6 +1,8 @@ pub use BinOpToken::*; pub use LitKind::*; pub use Nonterminal::*; +pub use NtExprKind::*; +pub use NtPatKind::*; pub use TokenKind::*; use crate::ast; @@ -871,6 +873,27 @@ impl PartialEq for Token { } } +#[derive(Debug, Copy, Clone, PartialEq, Eq, Encodable, Decodable)] +pub enum NtPatKind { + // Matches or-patterns. Was written using `pat` in edition 2021 or later. + PatWithOr, + // Doesn't match or-patterns. + // - `inferred`: was written using `pat` in edition 2015 or 2018. + // - `!inferred`: was written using `pat_param`. + PatParam { inferred: bool }, +} + +#[derive(Debug, Copy, Clone, PartialEq, Eq, Encodable, Decodable)] +pub enum NtExprKind { + // Matches expressions using the post-edition 2024. Was written using + // `expr` in edition 2024 or later. + Expr, + // Matches expressions using the pre-edition 2024 rules. + // - `inferred`: was written using `expr` in edition 2021 or earlier. + // - `!inferred`: was written using `expr_2021`. + Expr2021 { inferred: bool }, +} + #[derive(Clone, Encodable, Decodable)] /// For interpolation during macro expansion. pub enum Nonterminal { @@ -892,19 +915,8 @@ pub enum NonterminalKind { Item, Block, Stmt, - PatParam { - /// Keep track of whether the user used `:pat_param` or `:pat` and we inferred it from the - /// edition of the span. This is used for diagnostics. - inferred: bool, - }, - PatWithOr, - Expr, - /// Matches an expression using the rules from edition 2021 and earlier. - Expr2021 { - /// Keep track of whether the user used `:expr` or `:expr_2021` and we inferred it from the - /// edition of the span. This is used for diagnostics AND feature gating. - inferred: bool, - }, + Pat(NtPatKind), + Expr(NtExprKind), Ty, Ident, Lifetime, @@ -926,20 +938,22 @@ impl NonterminalKind { sym::item => NonterminalKind::Item, sym::block => NonterminalKind::Block, sym::stmt => NonterminalKind::Stmt, - sym::pat => match edition() { - Edition::Edition2015 | Edition::Edition2018 => { - NonterminalKind::PatParam { inferred: true } + sym::pat => { + if edition().at_least_rust_2021() { + NonterminalKind::Pat(PatWithOr) + } else { + NonterminalKind::Pat(PatParam { inferred: true }) } - Edition::Edition2021 | Edition::Edition2024 => NonterminalKind::PatWithOr, - }, - sym::pat_param => NonterminalKind::PatParam { inferred: false }, - sym::expr => match edition() { - Edition::Edition2015 | Edition::Edition2018 | Edition::Edition2021 => { - NonterminalKind::Expr2021 { inferred: true } + } + sym::pat_param => NonterminalKind::Pat(PatParam { inferred: false }), + sym::expr => { + if edition().at_least_rust_2024() { + NonterminalKind::Expr(Expr) + } else { + NonterminalKind::Expr(Expr2021 { inferred: true }) } - Edition::Edition2024 => NonterminalKind::Expr, - }, - sym::expr_2021 => NonterminalKind::Expr2021 { inferred: false }, + } + sym::expr_2021 => NonterminalKind::Expr(Expr2021 { inferred: false }), sym::ty => NonterminalKind::Ty, sym::ident => NonterminalKind::Ident, sym::lifetime => NonterminalKind::Lifetime, @@ -951,15 +965,16 @@ impl NonterminalKind { _ => return None, }) } + fn symbol(self) -> Symbol { match self { NonterminalKind::Item => sym::item, NonterminalKind::Block => sym::block, NonterminalKind::Stmt => sym::stmt, - NonterminalKind::PatParam { inferred: false } => sym::pat_param, - NonterminalKind::PatParam { inferred: true } | NonterminalKind::PatWithOr => sym::pat, - NonterminalKind::Expr | NonterminalKind::Expr2021 { inferred: true } => sym::expr, - NonterminalKind::Expr2021 { inferred: false } => sym::expr_2021, + NonterminalKind::Pat(PatParam { inferred: true } | PatWithOr) => sym::pat, + NonterminalKind::Pat(PatParam { inferred: false }) => sym::pat_param, + NonterminalKind::Expr(Expr2021 { inferred: true } | Expr) => sym::expr, + NonterminalKind::Expr(Expr2021 { inferred: false }) => sym::expr_2021, NonterminalKind::Ty => sym::ty, NonterminalKind::Ident => sym::ident, NonterminalKind::Lifetime => sym::lifetime, -- cgit 1.4.1-3-g733a5