From 9f089e080c47bc282aa98f1e8c72ff44076afbb9 Mon Sep 17 00:00:00 2001 From: Nicholas Nethercote Date: Thu, 27 Mar 2025 09:33:02 +1100 Subject: Add `{ast,hir,thir}::PatKind::Missing` variants. "Missing" patterns are possible in bare fn types (`fn f(u32)`) and similar places. Currently these are represented in the AST with `ast::PatKind::Ident` with no `by_ref`, no `mut`, an empty ident, and no sub-pattern. This flows through to `{hir,thir}::PatKind::Binding` for HIR and THIR. This is a bit nasty. It's very non-obvious, and easy to forget to check for the exceptional empty identifier case. This commit adds a new variant, `PatKind::Missing`, to do it properly. The process I followed: - Add a `Missing` variant to `{ast,hir,thir}::PatKind`. - Chang `parse_param_general` to produce `ast::PatKind::Missing` instead of `ast::PatKind::Missing`. - Look through `kw::Empty` occurrences to find functions where an existing empty ident check needs replacing with a `PatKind::Missing` check: `print_param`, `check_trait_item`, `is_named_param`. - Add a `PatKind::Missing => unreachable!(),` arm to every exhaustive match identified by the compiler. - Find which arms are actually reachable by running the test suite, changing them to something appropriate, usually by looking at what would happen to a `PatKind::Ident`/`PatKind::Binding` with no ref, no `mut`, an empty ident, and no subpattern. Quite a few of the `unreachable!()` arms were never reached. This makes sense because `PatKind::Missing` can't happen in every pattern, only in places like bare fn tys and trait fn decls. I also tried an alternative approach: modifying `ast::Param::pat` to hold an `Option>` instead of a `P`, but that quickly turned into a very large and painful change. Adding `PatKind::Missing` is much easier. --- src/tools/clippy/clippy_lints/src/equatable_if_let.rs | 1 + src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs | 1 + src/tools/clippy/clippy_lints/src/matches/single_match.rs | 1 + src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs | 1 + src/tools/clippy/clippy_lints/src/utils/author.rs | 1 + src/tools/clippy/clippy_utils/src/ast_utils/mod.rs | 1 + src/tools/clippy/clippy_utils/src/hir_utils.rs | 1 + src/tools/clippy/clippy_utils/src/lib.rs | 1 + src/tools/rustfmt/src/items.rs | 6 +----- src/tools/rustfmt/src/patterns.rs | 2 ++ 10 files changed, 11 insertions(+), 5 deletions(-) (limited to 'src/tools') diff --git a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs index cd9ab2764ac..3afb687040f 100644 --- a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs +++ b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs @@ -45,6 +45,7 @@ fn unary_pattern(pat: &Pat<'_>) -> bool { pats.iter().all(unary_pattern) } match &pat.kind { + PatKind::Missing => unreachable!(), PatKind::Slice(_, _, _) | PatKind::Range(_, _, _) | PatKind::Binding(..) diff --git a/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs b/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs index 250f17fa902..a21597ffb93 100644 --- a/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs +++ b/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs @@ -253,6 +253,7 @@ fn iter_matching_struct_fields<'a>( impl<'a> NormalizedPat<'a> { fn from_pat(cx: &LateContext<'_>, arena: &'a DroplessArena, pat: &'a Pat<'_>) -> Self { match pat.kind { + PatKind::Missing => unreachable!(), PatKind::Wild | PatKind::Binding(.., None) => Self::Wild, PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) diff --git a/src/tools/clippy/clippy_lints/src/matches/single_match.rs b/src/tools/clippy/clippy_lints/src/matches/single_match.rs index 56fbd626eef..836c46240ce 100644 --- a/src/tools/clippy/clippy_lints/src/matches/single_match.rs +++ b/src/tools/clippy/clippy_lints/src/matches/single_match.rs @@ -406,6 +406,7 @@ impl<'a> PatState<'a> { pats.iter().map(|p| p.pat), ), + PatKind::Missing => unreachable!(), PatKind::Wild | PatKind::Binding(_, _, _, None) | PatKind::Expr(_) diff --git a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs index f43715d6752..8966e6851ac 100644 --- a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs +++ b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs @@ -224,6 +224,7 @@ fn transform_with_focus_on_idx(alternatives: &mut ThinVec>, focus_idx: us // We're trying to find whatever kind (~"constructor") we found in `alternatives[start..]`. let changed = match &mut focus_kind { + Missing => unreachable!(), // These pattern forms are "leafs" and do not have sub-patterns. // Therefore they are not some form of constructor `C`, // with which a pattern `C(p_0)` may be formed, diff --git a/src/tools/clippy/clippy_lints/src/utils/author.rs b/src/tools/clippy/clippy_lints/src/utils/author.rs index 4309cd2c9ab..b7dcd2ffb0e 100644 --- a/src/tools/clippy/clippy_lints/src/utils/author.rs +++ b/src/tools/clippy/clippy_lints/src/utils/author.rs @@ -676,6 +676,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> { } match pat.value.kind { + PatKind::Missing => unreachable!(), PatKind::Wild => kind!("Wild"), PatKind::Never => kind!("Never"), PatKind::Binding(ann, _, name, sub) => { diff --git a/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs b/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs index 6023ae9cc7b..ed99f966d2b 100644 --- a/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs +++ b/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs @@ -33,6 +33,7 @@ pub fn eq_id(l: Ident, r: Ident) -> bool { pub fn eq_pat(l: &Pat, r: &Pat) -> bool { use PatKind::*; match (&l.kind, &r.kind) { + (Missing, _) | (_, Missing) => unreachable!(), (Paren(l), _) => eq_pat(l, r), (_, Paren(r)) => eq_pat(l, r), (Wild, Wild) | (Rest, Rest) => true, diff --git a/src/tools/clippy/clippy_utils/src/hir_utils.rs b/src/tools/clippy/clippy_utils/src/hir_utils.rs index 9938e64d242..b813cd361ed 100644 --- a/src/tools/clippy/clippy_utils/src/hir_utils.rs +++ b/src/tools/clippy/clippy_utils/src/hir_utils.rs @@ -1124,6 +1124,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> { pub fn hash_pat(&mut self, pat: &Pat<'_>) { std::mem::discriminant(&pat.kind).hash(&mut self.s); match pat.kind { + PatKind::Missing => unreachable!(), PatKind::Binding(BindingMode(by_ref, mutability), _, _, pat) => { std::mem::discriminant(&by_ref).hash(&mut self.s); std::mem::discriminant(&mutability).hash(&mut self.s); diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs index 1307ff79bc5..bdcbe1437d0 100644 --- a/src/tools/clippy/clippy_utils/src/lib.rs +++ b/src/tools/clippy/clippy_utils/src/lib.rs @@ -1857,6 +1857,7 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool { } match pat.kind { + PatKind::Missing => unreachable!(), PatKind::Wild | PatKind::Never => false, // If `!` typechecked then the type is empty, so not refutable. PatKind::Binding(_, _, _, pat) => pat.is_some_and(|pat| is_refutable(cx, pat)), PatKind::Box(pat) | PatKind::Ref(pat, _) => is_refutable(cx, pat), diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs index 3fb3284e3d7..81ff6327a4f 100644 --- a/src/tools/rustfmt/src/items.rs +++ b/src/tools/rustfmt/src/items.rs @@ -2433,11 +2433,7 @@ pub(crate) fn span_hi_for_param(context: &RewriteContext<'_>, param: &ast::Param } pub(crate) fn is_named_param(param: &ast::Param) -> bool { - if let ast::PatKind::Ident(_, ident, _) = param.pat.kind { - ident.name != symbol::kw::Empty - } else { - true - } + !matches!(param.pat.kind, ast::PatKind::Missing) } #[derive(Copy, Clone, Debug, PartialEq, Eq)] diff --git a/src/tools/rustfmt/src/patterns.rs b/src/tools/rustfmt/src/patterns.rs index bafed41e39f..8ec3de286dc 100644 --- a/src/tools/rustfmt/src/patterns.rs +++ b/src/tools/rustfmt/src/patterns.rs @@ -42,6 +42,7 @@ pub(crate) fn is_short_pattern( fn is_short_pattern_inner(context: &RewriteContext<'_>, pat: &ast::Pat) -> bool { match &pat.kind { + ast::PatKind::Missing => unreachable!(), ast::PatKind::Rest | ast::PatKind::Never | ast::PatKind::Wild | ast::PatKind::Err(_) => { true } @@ -100,6 +101,7 @@ impl Rewrite for Pat { fn rewrite_result(&self, context: &RewriteContext<'_>, shape: Shape) -> RewriteResult { match self.kind { + PatKind::Missing => unreachable!(), PatKind::Or(ref pats) => { let pat_strs = pats .iter() -- cgit 1.4.1-3-g733a5