diff options
| -rw-r--r-- | compiler/rustc_hir_typeck/src/pat.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/messages.ftl | 5 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/errors.rs | 10 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/thir/pattern/check_match.rs | 16 | ||||
| -rw-r--r-- | tests/ui/rfcs/rfc-0000-never_patterns/typeck.rs | 17 | ||||
| -rw-r--r-- | tests/ui/rfcs/rfc-0000-never_patterns/typeck.stderr | 66 |
6 files changed, 110 insertions, 7 deletions
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs index fe8c36dbe06..2060e01e1d6 100644 --- a/compiler/rustc_hir_typeck/src/pat.rs +++ b/compiler/rustc_hir_typeck/src/pat.rs @@ -178,8 +178,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let ty = match pat.kind { PatKind::Wild | PatKind::Err(_) => expected, - // FIXME(never_patterns): check the type is uninhabited. If that is not possible within - // typeck, do that in a later phase. + // We allow any type here; we ensure that the type is uninhabited during match checking. PatKind::Never => expected, PatKind::Lit(lt) => self.check_pat_lit(pat.span, lt, expected, ti), PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti), diff --git a/compiler/rustc_mir_build/messages.ftl b/compiler/rustc_mir_build/messages.ftl index 615b553434f..2f11cb123ee 100644 --- a/compiler/rustc_mir_build/messages.ftl +++ b/compiler/rustc_mir_build/messages.ftl @@ -234,6 +234,11 @@ mir_build_mutation_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsa mir_build_non_const_path = runtime values cannot be referenced in patterns +mir_build_non_empty_never_pattern = + mismatched types + .label = a never pattern must be used on an uninhabited type + .note = the matched value is of type `{$ty}` + mir_build_non_exhaustive_match_all_arms_guarded = match arms with guards don't count towards exhaustivity diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs index 61ad99acf38..e3cc21cef11 100644 --- a/compiler/rustc_mir_build/src/errors.rs +++ b/compiler/rustc_mir_build/src/errors.rs @@ -788,6 +788,16 @@ pub struct FloatPattern; #[diag(mir_build_pointer_pattern)] pub struct PointerPattern; +#[derive(Diagnostic)] +#[diag(mir_build_non_empty_never_pattern)] +#[note] +pub struct NonEmptyNeverPattern<'tcx> { + #[primary_span] + #[label] + pub span: Span, + pub ty: Ty<'tcx>, +} + #[derive(LintDiagnostic)] #[diag(mir_build_indirect_structural_match)] #[note(mir_build_type_not_structural_tip)] diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs index f6c5e4a5cd6..6b08f6eb7c5 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs @@ -276,10 +276,13 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> { } else { // Check the pattern for some things unrelated to exhaustiveness. let refutable = if cx.refutable { Refutable } else { Irrefutable }; + let mut err = Ok(()); pat.walk_always(|pat| { check_borrow_conflicts_in_at_patterns(self, pat); check_for_bindings_named_same_as_variants(self, pat, refutable); + err = err.and(check_never_pattern(cx, pat)); }); + err?; Ok(cx.pattern_arena.alloc(cx.lower_pat(pat))) } } @@ -811,6 +814,19 @@ fn check_for_bindings_named_same_as_variants( } } +/// Check that never patterns are only used on inhabited types. +fn check_never_pattern<'tcx>( + cx: &MatchCheckCtxt<'_, 'tcx>, + pat: &Pat<'tcx>, +) -> Result<(), ErrorGuaranteed> { + if let PatKind::Never = pat.kind { + if !cx.is_uninhabited(pat.ty) { + return Err(cx.tcx.dcx().emit_err(NonEmptyNeverPattern { span: pat.span, ty: pat.ty })); + } + } + Ok(()) +} + fn report_irrefutable_let_patterns( tcx: TyCtxt<'_>, id: HirId, diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/typeck.rs b/tests/ui/rfcs/rfc-0000-never_patterns/typeck.rs index 90ff34e2f02..333108e92c0 100644 --- a/tests/ui/rfcs/rfc-0000-never_patterns/typeck.rs +++ b/tests/ui/rfcs/rfc-0000-never_patterns/typeck.rs @@ -1,4 +1,3 @@ -// check-pass #![feature(never_patterns)] #![feature(exhaustive_patterns)] #![allow(incomplete_features)] @@ -17,40 +16,48 @@ fn safe_unwrap_result<T: Copy>(res: Result<T, Void>) { // Check we only accept `!` where we want to. fn never_pattern_typeck(void: Void) { - // FIXME(never_patterns): Don't accept on a non-empty type. + // Don't accept on a non-empty type. match () { !, + //~^ ERROR: mismatched types } match (0, false) { !, + //~^ ERROR: mismatched types } match (0, false) { (_, !), + //~^ ERROR: mismatched types } match Some(0) { None => {} Some(!), + //~^ ERROR: mismatched types } - // FIXME(never_patterns): Don't accept on an arbitrary type, even if there are no more branches. + // Don't accept on an arbitrary type, even if there are no more branches. match () { () => {} !, + //~^ ERROR: mismatched types } - // FIXME(never_patterns): Don't accept even on an empty branch. + // Don't accept even on an empty branch. match None::<Void> { None => {} !, + //~^ ERROR: mismatched types } match (&[] as &[Void]) { [] => {} !, + //~^ ERROR: mismatched types } - // FIXME(never_patterns): Let alone if the emptiness is behind a reference. + // Let alone if the emptiness is behind a reference. match None::<&Void> { None => {} !, + //~^ ERROR: mismatched types } // Participate in match ergonomics. diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/typeck.stderr b/tests/ui/rfcs/rfc-0000-never_patterns/typeck.stderr new file mode 100644 index 00000000000..8c0475894de --- /dev/null +++ b/tests/ui/rfcs/rfc-0000-never_patterns/typeck.stderr @@ -0,0 +1,66 @@ +error: mismatched types + --> $DIR/typeck.rs:21:9 + | +LL | !, + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `()` + +error: mismatched types + --> $DIR/typeck.rs:25:9 + | +LL | !, + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `(i32, bool)` + +error: mismatched types + --> $DIR/typeck.rs:29:13 + | +LL | (_, !), + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `bool` + +error: mismatched types + --> $DIR/typeck.rs:34:14 + | +LL | Some(!), + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `i32` + +error: mismatched types + --> $DIR/typeck.rs:41:9 + | +LL | !, + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `()` + +error: mismatched types + --> $DIR/typeck.rs:48:9 + | +LL | !, + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `Option<Void>` + +error: mismatched types + --> $DIR/typeck.rs:53:9 + | +LL | !, + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `[Void]` + +error: mismatched types + --> $DIR/typeck.rs:59:9 + | +LL | !, + | ^ a never pattern must be used on an uninhabited type + | + = note: the matched value is of type `Option<&Void>` + +error: aborting due to 8 previous errors + |