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Auto merge of #13167 - iDawer:exhaustive_patterns, r=Veykril
feat: Implement `feature(exhaustive_patterns)` from unstable Rust
Closes #12753
Recognize Rust's unstable `#![feature(exhaustive_patterns)]` (RFC 1872). Allow omitting visibly uninhabited variants from `match` expressions when the feature is on.
This adjusts match checking to the current implementation of the postponed RFC 1872 in rustc.
| -rw-r--r-- | crates/hir-def/src/nameres.rs | 11 | ||||
| -rw-r--r-- | crates/hir-def/src/nameres/collector.rs | 11 | ||||
| -rw-r--r-- | crates/hir-expand/src/name.rs | 1 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/expr.rs | 7 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs | 16 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/match_check/usefulness.rs | 29 | ||||
| -rw-r--r-- | crates/hir-ty/src/inhabitedness.rs | 173 | ||||
| -rw-r--r-- | crates/hir-ty/src/lib.rs | 1 | ||||
| -rw-r--r-- | crates/ide-diagnostics/src/handlers/missing_match_arms.rs | 44 |
9 files changed, 272 insertions, 21 deletions
diff --git a/crates/hir-def/src/nameres.rs b/crates/hir-def/src/nameres.rs index 45f631936d..fc8444394c 100644 --- a/crates/hir-def/src/nameres.rs +++ b/crates/hir-def/src/nameres.rs @@ -64,7 +64,7 @@ use hir_expand::{name::Name, InFile, MacroCallId, MacroDefId}; use itertools::Itertools; use la_arena::Arena; use profile::Count; -use rustc_hash::FxHashMap; +use rustc_hash::{FxHashMap, FxHashSet}; use stdx::format_to; use syntax::{ast, SmolStr}; @@ -114,6 +114,8 @@ pub struct DefMap { registered_attrs: Vec<SmolStr>, /// Custom tool modules registered with `#![register_tool]`. registered_tools: Vec<SmolStr>, + /// Unstable features of Rust enabled with `#![feature(A, B)]`. + unstable_features: FxHashSet<SmolStr>, edition: Edition, recursion_limit: Option<u32>, @@ -284,6 +286,7 @@ impl DefMap { modules, registered_attrs: Vec::new(), registered_tools: Vec::new(), + unstable_features: FxHashSet::default(), diagnostics: Vec::new(), } } @@ -314,6 +317,10 @@ impl DefMap { &self.registered_attrs } + pub fn is_unstable_feature_enabled(&self, feature: &str) -> bool { + self.unstable_features.contains(feature) + } + pub fn root(&self) -> LocalModuleId { self.root } @@ -483,6 +490,7 @@ impl DefMap { registered_tools, fn_proc_macro_mapping, derive_helpers_in_scope, + unstable_features, proc_macro_loading_error: _, block: _, edition: _, @@ -500,6 +508,7 @@ impl DefMap { registered_tools.shrink_to_fit(); fn_proc_macro_mapping.shrink_to_fit(); derive_helpers_in_scope.shrink_to_fit(); + unstable_features.shrink_to_fit(); for (_, module) in modules.iter_mut() { module.children.shrink_to_fit(); module.scope.shrink_to_fit(); diff --git a/crates/hir-def/src/nameres/collector.rs b/crates/hir-def/src/nameres/collector.rs index 8a6bb929c3..ee27aa2554 100644 --- a/crates/hir-def/src/nameres/collector.rs +++ b/crates/hir-def/src/nameres/collector.rs @@ -294,6 +294,17 @@ impl DefCollector<'_> { continue; } + if *attr_name == hir_expand::name![feature] { + let features = + attr.parse_path_comma_token_tree().into_iter().flatten().filter_map( + |feat| match feat.segments() { + [name] => Some(name.to_smol_str()), + _ => None, + }, + ); + self.def_map.unstable_features.extend(features); + } + let attr_is_register_like = *attr_name == hir_expand::name![register_attr] || *attr_name == hir_expand::name![register_tool]; if !attr_is_register_like { diff --git a/crates/hir-expand/src/name.rs b/crates/hir-expand/src/name.rs index 2b859f7750..4ce21a5796 100644 --- a/crates/hir-expand/src/name.rs +++ b/crates/hir-expand/src/name.rs @@ -336,6 +336,7 @@ pub mod known { test, test_case, recursion_limit, + feature, // Safe intrinsics abort, add_with_overflow, diff --git a/crates/hir-ty/src/diagnostics/expr.rs b/crates/hir-ty/src/diagnostics/expr.rs index 642e03edd2..c8df4c796e 100644 --- a/crates/hir-ty/src/diagnostics/expr.rs +++ b/crates/hir-ty/src/diagnostics/expr.rs @@ -159,12 +159,7 @@ impl ExprValidator { } let pattern_arena = Arena::new(); - let cx = MatchCheckCtx { - module: self.owner.module(db.upcast()), - body: self.owner, - db, - pattern_arena: &pattern_arena, - }; + let cx = MatchCheckCtx::new(self.owner.module(db.upcast()), self.owner, db, &pattern_arena); let mut m_arms = Vec::with_capacity(arms.len()); let mut has_lowering_errors = false; diff --git a/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs b/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs index bbbe539c13..47d60fc41e 100644 --- a/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs +++ b/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs @@ -52,7 +52,10 @@ use hir_def::{EnumVariantId, HasModule, LocalFieldId, VariantId}; use smallvec::{smallvec, SmallVec}; use stdx::never; -use crate::{infer::normalize, AdtId, Interner, Scalar, Ty, TyExt, TyKind}; +use crate::{ + infer::normalize, inhabitedness::is_enum_variant_uninhabited_from, AdtId, Interner, Scalar, Ty, + TyExt, TyKind, +}; use super::{ is_box, @@ -557,8 +560,8 @@ impl SplitWildcard { TyKind::Scalar(Scalar::Bool) => smallvec![make_range(0, 1, Scalar::Bool)], // TyKind::Array(..) if ... => unhandled(), TyKind::Array(..) | TyKind::Slice(..) => unhandled(), - &TyKind::Adt(AdtId(hir_def::AdtId::EnumId(enum_id)), ..) => { - let enum_data = cx.db.enum_data(enum_id); + TyKind::Adt(AdtId(hir_def::AdtId::EnumId(enum_id)), subst) => { + let enum_data = cx.db.enum_data(*enum_id); // If the enum is declared as `#[non_exhaustive]`, we treat it as if it had an // additional "unknown" constructor. @@ -591,14 +594,15 @@ impl SplitWildcard { let mut ctors: SmallVec<[_; 1]> = enum_data .variants .iter() - .filter(|&(_, _v)| { + .map(|(local_id, _)| EnumVariantId { parent: *enum_id, local_id }) + .filter(|&variant| { // If `exhaustive_patterns` is enabled, we exclude variants known to be // uninhabited. let is_uninhabited = is_exhaustive_pat_feature - && unimplemented!("after MatchCheckCtx.feature_exhaustive_patterns()"); + && is_enum_variant_uninhabited_from(variant, subst, cx.module, cx.db); !is_uninhabited }) - .map(|(local_id, _)| Variant(EnumVariantId { parent: enum_id, local_id })) + .map(Variant) .collect(); if is_secretly_empty || is_declared_nonexhaustive { diff --git a/crates/hir-ty/src/diagnostics/match_check/usefulness.rs b/crates/hir-ty/src/diagnostics/match_check/usefulness.rs index 1221327b95..c4d709a975 100644 --- a/crates/hir-ty/src/diagnostics/match_check/usefulness.rs +++ b/crates/hir-ty/src/diagnostics/match_check/usefulness.rs @@ -277,7 +277,7 @@ use hir_def::{AdtId, DefWithBodyId, HasModule, ModuleId}; use smallvec::{smallvec, SmallVec}; use typed_arena::Arena; -use crate::{db::HirDatabase, Ty, TyExt}; +use crate::{db::HirDatabase, inhabitedness::is_ty_uninhabited_from, Ty, TyExt}; use super::deconstruct_pat::{Constructor, DeconstructedPat, Fields, SplitWildcard}; @@ -289,13 +289,27 @@ pub(crate) struct MatchCheckCtx<'a, 'p> { pub(crate) db: &'a dyn HirDatabase, /// Lowered patterns from arms plus generated by the check. pub(crate) pattern_arena: &'p Arena<DeconstructedPat<'p>>, + exhaustive_patterns: bool, } impl<'a, 'p> MatchCheckCtx<'a, 'p> { - pub(super) fn is_uninhabited(&self, _ty: &Ty) -> bool { - // FIXME(iDawer) implement exhaustive_patterns feature. More info in: - // Tracking issue for RFC 1872: exhaustive_patterns feature https://github.com/rust-lang/rust/issues/51085 - false + pub(crate) fn new( + module: ModuleId, + body: DefWithBodyId, + db: &'a dyn HirDatabase, + pattern_arena: &'p Arena<DeconstructedPat<'p>>, + ) -> Self { + let def_map = db.crate_def_map(module.krate()); + let exhaustive_patterns = def_map.is_unstable_feature_enabled("exhaustive_patterns"); + Self { module, body, db, pattern_arena, exhaustive_patterns } + } + + pub(super) fn is_uninhabited(&self, ty: &Ty) -> bool { + if self.feature_exhaustive_patterns() { + is_ty_uninhabited_from(ty, self.module, self.db) + } else { + false + } } /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`. @@ -311,10 +325,9 @@ impl<'a, 'p> MatchCheckCtx<'a, 'p> { } } - // Rust feature described as "Allows exhaustive pattern matching on types that contain uninhabited types." + // Rust's unstable feature described as "Allows exhaustive pattern matching on types that contain uninhabited types." pub(super) fn feature_exhaustive_patterns(&self) -> bool { - // FIXME see MatchCheckCtx::is_uninhabited - false + self.exhaustive_patterns } } diff --git a/crates/hir-ty/src/inhabitedness.rs b/crates/hir-ty/src/inhabitedness.rs new file mode 100644 index 0000000000..0c547192ac --- /dev/null +++ b/crates/hir-ty/src/inhabitedness.rs @@ -0,0 +1,173 @@ +//! Type inhabitedness logic. +use std::ops::ControlFlow::{self, Break, Continue}; + +use chalk_ir::{ + visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor}, + DebruijnIndex, +}; +use hir_def::{ + adt::VariantData, attr::Attrs, type_ref::ConstScalar, visibility::Visibility, AdtId, + EnumVariantId, HasModule, Lookup, ModuleId, VariantId, +}; + +use crate::{ + db::HirDatabase, Binders, ConcreteConst, Const, ConstValue, Interner, Substitution, Ty, TyKind, +}; + +/// Checks whether a type is visibly uninhabited from a particular module. +pub(crate) fn is_ty_uninhabited_from(ty: &Ty, target_mod: ModuleId, db: &dyn HirDatabase) -> bool { + let mut uninhabited_from = UninhabitedFrom { target_mod, db }; + let inhabitedness = ty.visit_with(&mut uninhabited_from, DebruijnIndex::INNERMOST); + inhabitedness == BREAK_VISIBLY_UNINHABITED +} + +/// Checks whether a variant is visibly uninhabited from a particular module. +pub(crate) fn is_enum_variant_uninhabited_from( + variant: EnumVariantId, + subst: &Substitution, + target_mod: ModuleId, + db: &dyn HirDatabase, +) -> bool { + let enum_data = db.enum_data(variant.parent); + let vars_attrs = db.variants_attrs(variant.parent); + let is_local = variant.parent.lookup(db.upcast()).container.krate() == target_mod.krate(); + + let mut uninhabited_from = UninhabitedFrom { target_mod, db }; + let inhabitedness = uninhabited_from.visit_variant( + variant.into(), + &enum_data.variants[variant.local_id].variant_data, + subst, + &vars_attrs[variant.local_id], + is_local, + ); + inhabitedness == BREAK_VISIBLY_UNINHABITED +} + +struct UninhabitedFrom<'a> { + target_mod: ModuleId, + db: &'a dyn HirDatabase, +} + +const CONTINUE_OPAQUELY_INHABITED: ControlFlow<VisiblyUninhabited> = Continue(()); +const BREAK_VISIBLY_UNINHABITED: ControlFlow<VisiblyUninhabited> = Break(VisiblyUninhabited); +#[derive(PartialEq, Eq)] +struct VisiblyUninhabited; + +impl TypeVisitor<Interner> for UninhabitedFrom<'_> { + type BreakTy = VisiblyUninhabited; + + fn as_dyn(&mut self) -> &mut dyn TypeVisitor<Interner, BreakTy = VisiblyUninhabited> { + self + } + + fn visit_ty( + &mut self, + ty: &Ty, + outer_binder: DebruijnIndex, + ) -> ControlFlow<VisiblyUninhabited> { + match ty.kind(Interner) { + TyKind::Adt(adt, subst) => self.visit_adt(adt.0, subst), + TyKind::Never => BREAK_VISIBLY_UNINHABITED, + TyKind::Tuple(..) => ty.super_visit_with(self, outer_binder), + TyKind::Array(item_ty, len) => match try_usize_const(len) { + Some(0) | None => CONTINUE_OPAQUELY_INHABITED, + Some(1..) => item_ty.super_visit_with(self, outer_binder), + }, + + TyKind::Ref(..) | _ => CONTINUE_OPAQUELY_INHABITED, + } + } + + fn interner(&self) -> Interner { + Interner + } +} + +impl UninhabitedFrom<'_> { + fn visit_adt(&mut self, adt: AdtId, subst: &Substitution) -> ControlFlow<VisiblyUninhabited> { + let attrs = self.db.attrs(adt.into()); + let adt_non_exhaustive = attrs.by_key("non_exhaustive").exists(); + let is_local = adt.module(self.db.upcast()).krate() == self.target_mod.krate(); + if adt_non_exhaustive && !is_local { + return CONTINUE_OPAQUELY_INHABITED; + } + + // An ADT is uninhabited iff all its variants uninhabited. + match adt { + // rustc: For now, `union`s are never considered uninhabited. + AdtId::UnionId(_) => CONTINUE_OPAQUELY_INHABITED, + AdtId::StructId(s) => { + let struct_data = self.db.struct_data(s); + self.visit_variant(s.into(), &struct_data.variant_data, subst, &attrs, is_local) + } + AdtId::EnumId(e) => { + let vars_attrs = self.db.variants_attrs(e); + let enum_data = self.db.enum_data(e); + + for (local_id, enum_var) in enum_data.variants.iter() { + let variant_inhabitedness = self.visit_variant( + EnumVariantId { parent: e, local_id }.into(), + &enum_var.variant_data, + subst, + &vars_attrs[local_id], + is_local, + ); + match variant_inhabitedness { + Break(VisiblyUninhabited) => continue, + Continue(()) => return CONTINUE_OPAQUELY_INHABITED, + } + } + BREAK_VISIBLY_UNINHABITED + } + } + } + + fn visit_variant( + &mut self, + variant: VariantId, + variant_data: &VariantData, + subst: &Substitution, + attrs: &Attrs, + is_local: bool, + ) -> ControlFlow<VisiblyUninhabited> { + let non_exhaustive_field_list = attrs.by_key("non_exhaustive").exists(); + if non_exhaustive_field_list && !is_local { + return CONTINUE_OPAQUELY_INHABITED; + } + + let is_enum = matches!(variant, VariantId::EnumVariantId(..)); + let field_tys = self.db.field_types(variant); + let field_vis = self.db.field_visibilities(variant); + + for (fid, _) in variant_data.fields().iter() { + self.visit_field(field_vis[fid], &field_tys[fid], subst, is_enum)?; + } + CONTINUE_OPAQUELY_INHABITED + } + + fn visit_field( + &mut self, + vis: Visibility, + ty: &Binders<Ty>, + subst: &Substitution, + is_enum: bool, + ) -> ControlFlow<VisiblyUninhabited> { + if is_enum || vis.is_visible_from(self.db.upcast(), self.target_mod) { + let ty = ty.clone().substitute(Interner, subst); + ty.visit_with(self, DebruijnIndex::INNERMOST) + } else { + CONTINUE_OPAQUELY_INHABITED + } + } +} + +fn try_usize_const(c: &Const) -> Option<u128> { + let data = &c.data(Interner); + if data.ty.kind(Interner) != &TyKind::Scalar(chalk_ir::Scalar::Uint(chalk_ir::UintTy::Usize)) { + return None; + } + match data.value { + ConstValue::Concrete(ConcreteConst { interned: ConstScalar::UInt(value) }) => Some(value), + _ => None, + } +} diff --git a/crates/hir-ty/src/lib.rs b/crates/hir-ty/src/lib.rs index 5a5d610e36..a82a331d4b 100644 --- a/crates/hir-ty/src/lib.rs +++ b/crates/hir-ty/src/lib.rs @@ -14,6 +14,7 @@ mod chalk_db; mod chalk_ext; pub mod consteval; mod infer; +mod inhabitedness; mod interner; mod lower; mod mapping; diff --git a/crates/ide-diagnostics/src/handlers/missing_match_arms.rs b/crates/ide-diagnostics/src/handlers/missing_match_arms.rs index 5fcaf405b1..c24430ce60 100644 --- a/crates/ide-diagnostics/src/handlers/missing_match_arms.rs +++ b/crates/ide-diagnostics/src/handlers/missing_match_arms.rs @@ -947,6 +947,50 @@ fn f() { ); } + mod rust_unstable { + use super::*; + + #[test] + fn rfc_1872_exhaustive_patterns() { + check_diagnostics_no_bails( + r" +//- minicore: option, result +#![feature(exhaustive_patterns)] +enum Void {} +fn test() { + match None::<!> { None => () } + match Result::<u8, !>::Ok(2) { Ok(_) => () } + match Result::<u8, Void>::Ok(2) { Ok(_) => () } + match (2, loop {}) {} + match Result::<!, !>::Ok(loop {}) {} + match (&loop {}) {} // https://github.com/rust-lang/rust/issues/50642#issuecomment-388234919 + // ^^^^^^^^^^ error: missing match arm: type `&!` is non-empty +}", + ); + } + + #[test] + fn rfc_1872_private_uninhabitedness() { + check_diagnostics_no_bails( + r" +//- minicore: option +//- /lib.rs crate:lib +#![feature(exhaustive_patterns)] +pub struct PrivatelyUninhabited { private_field: Void } +enum Void {} +fn test_local(x: Option<PrivatelyUninhabited>) { + match x {} +} // ^ error: missing match arm: `None` not covered +//- /main.rs crate:main deps:lib +#![feature(exhaustive_patterns)] +fn test(x: Option<lib::PrivatelyUninhabited>) { + match x {} + // ^ error: missing match arm: `None` and `Some(_)` not covered +}", + ); + } + } + mod false_negatives { //! The implementation of match checking here is a work in progress. As we roll this out, we //! prefer false negatives to false positives (ideally there would be no false positives). This |