diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_lint_defs/src/builtin.rs | 52 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/messages.ftl | 3 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/errors.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs | 37 |
4 files changed, 89 insertions, 9 deletions
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs index 21575bf6b04..69b462d32bd 100644 --- a/compiler/rustc_lint_defs/src/builtin.rs +++ b/compiler/rustc_lint_defs/src/builtin.rs @@ -2312,6 +2312,57 @@ declare_lint! { } declare_lint! { + /// The `const_patterns_without_partial_eq` lint detects constants that are used in patterns, + /// whose type does not implement `PartialEq`. + /// + /// ### Example + /// + /// ```rust,compile_fail + /// #![deny(const_patterns_without_partial_eq)] + /// + /// trait EnumSetType { + /// type Repr; + /// } + /// + /// enum Enum8 { } + /// impl EnumSetType for Enum8 { + /// type Repr = u8; + /// } + /// + /// #[derive(PartialEq, Eq)] + /// struct EnumSet<T: EnumSetType> { + /// __enumset_underlying: T::Repr, + /// } + /// + /// const CONST_SET: EnumSet<Enum8> = EnumSet { __enumset_underlying: 3 }; + /// + /// fn main() { + /// match CONST_SET { + /// CONST_SET => { /* ok */ } + /// _ => panic!("match fell through?"), + /// } + /// } + /// ``` + /// + /// {{produces}} + /// + /// ### Explanation + /// + /// Previous versions of Rust accepted constants in patterns, even if those constants' types + /// did not have `PartialEq` implemented. The compiler falls back to comparing the value + /// field-by-field. In the future we'd like to ensure that pattern matching always + /// follows `PartialEq` semantics, so that trait bound will become a requirement for + /// matching on constants. + pub CONST_PATTERNS_WITHOUT_PARTIAL_EQ, + Warn, + "constant in pattern does not implement `PartialEq`", + @future_incompatible = FutureIncompatibleInfo { + reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps, + reference: "issue #116122 <https://github.com/rust-lang/rust/issues/116122>", + }; +} + +declare_lint! { /// The `ambiguous_associated_items` lint detects ambiguity between /// [associated items] and [enum variants]. /// @@ -3357,6 +3408,7 @@ declare_lint_pass! { CONFLICTING_REPR_HINTS, CONST_EVALUATABLE_UNCHECKED, CONST_ITEM_MUTATION, + CONST_PATTERNS_WITHOUT_PARTIAL_EQ, DEAD_CODE, DEPRECATED, DEPRECATED_CFG_ATTR_CRATE_TYPE_NAME, diff --git a/compiler/rustc_mir_build/messages.ftl b/compiler/rustc_mir_build/messages.ftl index 938f3edd31b..ce021923f64 100644 --- a/compiler/rustc_mir_build/messages.ftl +++ b/compiler/rustc_mir_build/messages.ftl @@ -229,6 +229,9 @@ mir_build_non_exhaustive_patterns_type_not_empty = non-exhaustive patterns: type .suggestion = ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown .help = ensure that all possible cases are being handled by adding a match arm with a wildcard pattern +mir_build_non_partial_eq_match = + to use a constant of type `{$non_peq_ty}` in a pattern, the type must implement `PartialEq` + mir_build_nontrivial_structural_match = to use a constant of type `{$non_sm_ty}` in a pattern, the constant's initializer must be trivial or `{$non_sm_ty}` must be annotated with `#[derive(PartialEq, Eq)]` diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs index 3ff3387a781..bee5ac550dd 100644 --- a/compiler/rustc_mir_build/src/errors.rs +++ b/compiler/rustc_mir_build/src/errors.rs @@ -749,6 +749,12 @@ pub struct NontrivialStructuralMatch<'tcx> { } #[derive(LintDiagnostic)] +#[diag(mir_build_non_partial_eq_match)] +pub struct NonPartialEqMatch<'tcx> { + pub non_peq_ty: Ty<'tcx>, +} + +#[derive(LintDiagnostic)] #[diag(mir_build_overlapping_range_endpoints)] #[note] pub struct OverlappingRangeEndpoints<'tcx> { diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs index 00d9fe72cfc..4758ace73b6 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs @@ -16,8 +16,8 @@ use std::cell::Cell; use super::PatCtxt; use crate::errors::{ - FloatPattern, IndirectStructuralMatch, InvalidPattern, NontrivialStructuralMatch, - PointerPattern, TypeNotStructural, UnionPattern, UnsizedPattern, + FloatPattern, IndirectStructuralMatch, InvalidPattern, NonPartialEqMatch, + NontrivialStructuralMatch, PointerPattern, TypeNotStructural, UnionPattern, UnsizedPattern, }; impl<'a, 'tcx> PatCtxt<'a, 'tcx> { @@ -155,8 +155,9 @@ impl<'tcx> ConstToPat<'tcx> { }; if !self.saw_const_match_error.get() { - // If we were able to successfully convert the const to some pat, - // double-check that all types in the const implement `Structural`. + // If we were able to successfully convert the const to some pat (possibly with some + // lints, but no errors), double-check that all types in the const implement + // `Structural` and `PartialEq`. let structural = traits::search_for_structural_match_violation(self.span, self.tcx(), cv.ty()); @@ -178,7 +179,7 @@ impl<'tcx> ConstToPat<'tcx> { } if let Some(non_sm_ty) = structural { - if !self.type_may_have_partial_eq_impl(cv.ty()) { + if !self.type_has_partial_eq_impl(cv.ty()) { if let ty::Adt(def, ..) = non_sm_ty.kind() { if def.is_union() { let err = UnionPattern { span: self.span }; @@ -192,8 +193,10 @@ impl<'tcx> ConstToPat<'tcx> { } else { let err = InvalidPattern { span: self.span, non_sm_ty }; self.tcx().sess.emit_err(err); - return Box::new(Pat { span: self.span, ty: cv.ty(), kind: PatKind::Wild }); } + // All branches above emitted an error. Don't print any more lints. + // The pattern we return is irrelevant since we errored. + return Box::new(Pat { span: self.span, ty: cv.ty(), kind: PatKind::Wild }); } else if !self.saw_const_match_lint.get() { if let Some(mir_structural_match_violation) = mir_structural_match_violation { match non_sm_ty.kind() { @@ -238,13 +241,24 @@ impl<'tcx> ConstToPat<'tcx> { _ => {} } } + + // Always check for `PartialEq`, even if we emitted other lints. (But not if there were + // any errors.) This ensures it shows up in cargo's future-compat reports as well. + if !self.type_has_partial_eq_impl(cv.ty()) { + self.tcx().emit_spanned_lint( + lint::builtin::CONST_PATTERNS_WITHOUT_PARTIAL_EQ, + self.id, + self.span, + NonPartialEqMatch { non_peq_ty: cv.ty() }, + ); + } } inlined_const_as_pat } #[instrument(level = "trace", skip(self), ret)] - fn type_may_have_partial_eq_impl(&self, ty: Ty<'tcx>) -> bool { + fn type_has_partial_eq_impl(&self, ty: Ty<'tcx>) -> bool { // double-check there even *is* a semantic `PartialEq` to dispatch to. // // (If there isn't, then we can safely issue a hard @@ -259,8 +273,13 @@ impl<'tcx> ConstToPat<'tcx> { ty::TraitRef::new(self.tcx(), partial_eq_trait_id, [ty, ty]), ); - // FIXME: should this call a `predicate_must_hold` variant instead? - self.infcx.predicate_may_hold(&partial_eq_obligation) + // This *could* accept a type that isn't actually `PartialEq`, because region bounds get + // ignored. However that should be pretty much impossible since consts that do not depend on + // generics can only mention the `'static` lifetime, and how would one have a type that's + // `PartialEq` for some lifetime but *not* for `'static`? If this ever becomes a problem + // we'll need to leave some sort of trace of this requirement in the MIR so that borrowck + // can ensure that the type really implements `PartialEq`. + self.infcx.predicate_must_hold_modulo_regions(&partial_eq_obligation) } fn field_pats( |