diff options
8 files changed, 47 insertions, 24 deletions
diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs index 4ce868f014f..f7a4931c111 100644 --- a/compiler/rustc_pattern_analysis/src/constructor.rs +++ b/compiler/rustc_pattern_analysis/src/constructor.rs @@ -696,6 +696,10 @@ pub enum Constructor<Cx: PatCx> { F128Range(IeeeFloat<QuadS>, IeeeFloat<QuadS>, RangeEnd), /// String literals. Strings are not quite the same as `&[u8]` so we treat them separately. Str(Cx::StrLit), + /// Deref patterns (enabled by the `deref_patterns` feature) provide a way of matching on a + /// smart pointer ADT through its pointee. They don't directly correspond to ADT constructors, + /// and currently are not supported alongside them. Carries the type of the pointee. + DerefPattern(Cx::Ty), /// Constants that must not be matched structurally. They are treated as black boxes for the /// purposes of exhaustiveness: we must not inspect them, and they don't count towards making a /// match exhaustive. @@ -740,6 +744,7 @@ impl<Cx: PatCx> Clone for Constructor<Cx> { Constructor::F64Range(lo, hi, end) => Constructor::F64Range(*lo, *hi, *end), Constructor::F128Range(lo, hi, end) => Constructor::F128Range(*lo, *hi, *end), Constructor::Str(value) => Constructor::Str(value.clone()), + Constructor::DerefPattern(ty) => Constructor::DerefPattern(ty.clone()), Constructor::Opaque(inner) => Constructor::Opaque(inner.clone()), Constructor::Or => Constructor::Or, Constructor::Never => Constructor::Never, @@ -856,6 +861,10 @@ impl<Cx: PatCx> Constructor<Cx> { } (Slice(self_slice), Slice(other_slice)) => self_slice.is_covered_by(*other_slice), + // Deref patterns only interact with other deref patterns. Prior to usefulness analysis, + // we ensure they don't appear alongside any other non-wild non-opaque constructors. + (DerefPattern(_), DerefPattern(_)) => true, + // Opaque constructors don't interact with anything unless they come from the // syntactically identical pattern. (Opaque(self_id), Opaque(other_id)) => self_id == other_id, @@ -932,6 +941,7 @@ impl<Cx: PatCx> Constructor<Cx> { F64Range(lo, hi, end) => write!(f, "{lo}{end}{hi}")?, F128Range(lo, hi, end) => write!(f, "{lo}{end}{hi}")?, Str(value) => write!(f, "{value:?}")?, + DerefPattern(_) => write!(f, "deref!({:?})", fields.next().unwrap())?, Opaque(..) => write!(f, "<constant pattern>")?, Or => { for pat in fields { @@ -1039,8 +1049,17 @@ impl<Cx: PatCx> ConstructorSet<Cx> { let mut missing = Vec::new(); // Constructors in `ctors`, except wildcards and opaques. let mut seen = Vec::new(); + // If we see a deref pattern, it must be the only non-wildcard non-opaque constructor; we + // ensure this prior to analysis. + let mut deref_pat_present = false; for ctor in ctors.cloned() { match ctor { + DerefPattern(..) => { + if !deref_pat_present { + deref_pat_present = true; + present.push(ctor); + } + } Opaque(..) => present.push(ctor), Wildcard => {} // discard wildcards _ => seen.push(ctor), @@ -1048,6 +1067,9 @@ impl<Cx: PatCx> ConstructorSet<Cx> { } match self { + _ if deref_pat_present => { + // Deref patterns are the only constructor; nothing is missing. + } ConstructorSet::Struct { empty } => { if !seen.is_empty() { present.push(Struct); diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs index 7c12f69f14c..050b48d082b 100644 --- a/compiler/rustc_pattern_analysis/src/rustc.rs +++ b/compiler/rustc_pattern_analysis/src/rustc.rs @@ -269,6 +269,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> { } _ => bug!("bad slice pattern {:?} {:?}", ctor, ty), }, + DerefPattern(pointee_ty) => reveal_and_alloc(cx, once(pointee_ty.inner())), Bool(..) | IntRange(..) | F16Range(..) | F32Range(..) | F64Range(..) | F128Range(..) | Str(..) | Opaque(..) | Never | NonExhaustive | Hidden | Missing | PrivateUninhabited | Wildcard => &[], @@ -296,7 +297,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> { } _ => bug!("Unexpected type for constructor `{ctor:?}`: {ty:?}"), }, - Ref => 1, + Ref | DerefPattern(_) => 1, Slice(slice) => slice.arity(), Bool(..) | IntRange(..) | F16Range(..) | F32Range(..) | F64Range(..) | F128Range(..) | Str(..) | Opaque(..) | Never | NonExhaustive | Hidden | Missing @@ -493,11 +494,15 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> { ), }; } - PatKind::DerefPattern { .. } => { - // FIXME(deref_patterns): At least detect that `box _` is irrefutable. - fields = vec![]; - arity = 0; - ctor = Opaque(OpaqueId::new()); + PatKind::DerefPattern { subpattern, .. } => { + // NB(deref_patterns): This assumes the deref pattern is matching on a trusted + // `DerefPure` type. If the `Deref` impl isn't trusted, exhaustiveness must take + // into account that multiple calls to deref may return different results. Hence + // multiple deref! patterns cannot be exhaustive together unless each is exhaustive + // by itself. + fields = vec![self.lower_pat(subpattern).at_index(0)]; + arity = 1; + ctor = DerefPattern(cx.reveal_opaque_ty(subpattern.ty)); } PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => { match ty.kind() { @@ -874,6 +879,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> { print::write_ref_like(&mut s, pat.ty().inner(), &print(&pat.fields[0])).unwrap(); s } + DerefPattern(_) => format!("deref!({})", print(&pat.fields[0])), Slice(slice) => { let (prefix_len, has_dot_dot) = match slice.kind { SliceKind::FixedLen(len) => (len, false), diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs index 11ebbea07fa..53638f2a57d 100644 --- a/compiler/rustc_pattern_analysis/src/usefulness.rs +++ b/compiler/rustc_pattern_analysis/src/usefulness.rs @@ -702,6 +702,7 @@ //! - `ui/consts/const_in_pattern` //! - `ui/rfc-2008-non-exhaustive` //! - `ui/half-open-range-patterns` +//! - `ui/pattern/deref-patterns` //! - probably many others //! //! I (Nadrieril) prefer to put new tests in `ui/pattern/usefulness` unless there's a specific @@ -866,7 +867,8 @@ impl PlaceValidity { /// inside `&` and union fields where validity is reset to `MaybeInvalid`. fn specialize<Cx: PatCx>(self, ctor: &Constructor<Cx>) -> Self { // We preserve validity except when we go inside a reference or a union field. - if matches!(ctor, Constructor::Ref | Constructor::UnionField) { + if matches!(ctor, Constructor::Ref | Constructor::DerefPattern(_) | Constructor::UnionField) + { // Validity of `x: &T` does not imply validity of `*x: T`. MaybeInvalid } else { diff --git a/src/doc/unstable-book/src/language-features/deref-patterns.md b/src/doc/unstable-book/src/language-features/deref-patterns.md index fb6df290cc1..4c3d456b9af 100644 --- a/src/doc/unstable-book/src/language-features/deref-patterns.md +++ b/src/doc/unstable-book/src/language-features/deref-patterns.md @@ -60,8 +60,7 @@ Like [`box_patterns`], deref patterns may move out of boxes: # #![feature(deref_patterns)] # #![allow(incomplete_features)] struct NoCopy; -// Match exhaustiveness analysis is not yet implemented. -let deref!(x) = Box::new(NoCopy) else { unreachable!() }; +let deref!(x) = Box::new(NoCopy); drop::<NoCopy>(x); ``` diff --git a/tests/ui/pattern/deref-patterns/bindings.rs b/tests/ui/pattern/deref-patterns/bindings.rs index ac48e3ffefc..92c01d737ba 100644 --- a/tests/ui/pattern/deref-patterns/bindings.rs +++ b/tests/ui/pattern/deref-patterns/bindings.rs @@ -13,7 +13,6 @@ fn simple_vec(vec: Vec<u32>) -> u32 { deref!([x]) => x, deref!([1, x]) => x + 200, deref!(ref slice) => slice.iter().sum(), - _ => 2000, } } @@ -25,7 +24,6 @@ fn simple_vec(vec: Vec<u32>) -> u32 { [x] => x, [1, x] => x + 200, deref!(ref slice) => slice.iter().sum(), - _ => 2000, } } diff --git a/tests/ui/pattern/deref-patterns/closure_capture.rs b/tests/ui/pattern/deref-patterns/closure_capture.rs index cf78eeda1d5..497ec622b0c 100644 --- a/tests/ui/pattern/deref-patterns/closure_capture.rs +++ b/tests/ui/pattern/deref-patterns/closure_capture.rs @@ -9,7 +9,7 @@ struct NoCopy; fn main() { let b = Rc::new("aaa".to_string()); let f = || { - let deref!(ref s) = b else { unreachable!() }; + let deref!(ref s) = b; assert_eq!(s.len(), 3); }; assert_eq!(b.len(), 3); @@ -26,7 +26,7 @@ fn main() { let mut b = "aaa".to_string(); let mut f = || { - let deref!(ref mut s) = b else { unreachable!() }; + let deref!(ref mut s) = b; s.make_ascii_uppercase(); }; f(); @@ -53,7 +53,7 @@ fn main() { let b = Box::new(NoCopy); let f = || { // this should move out of the box rather than borrow. - let deref!(x) = b else { unreachable!() }; + let deref!(x) = b; drop::<NoCopy>(x); }; f(); @@ -61,7 +61,7 @@ fn main() { let b = Box::new((NoCopy,)); let f = || { // this should move out of the box rather than borrow. - let (x,) = b else { unreachable!() }; + let (x,) = b; drop::<NoCopy>(x); }; f(); diff --git a/tests/ui/pattern/deref-patterns/deref-box.rs b/tests/ui/pattern/deref-patterns/deref-box.rs index 2d0a8d01972..39b23dcab51 100644 --- a/tests/ui/pattern/deref-patterns/deref-box.rs +++ b/tests/ui/pattern/deref-patterns/deref-box.rs @@ -6,18 +6,18 @@ #![expect(incomplete_features)] fn unbox_1<T>(b: Box<T>) -> T { - let deref!(x) = b else { unreachable!() }; + let deref!(x) = b; x } fn unbox_2<T>(b: Box<(T,)>) -> T { - let (x,) = b else { unreachable!() }; + let (x,) = b; x } fn unbox_separately<T>(b: Box<(T, T)>) -> (T, T) { - let (x, _) = b else { unreachable!() }; - let (_, y) = b else { unreachable!() }; + let (x, _) = b; + let (_, y) = b; (x, y) } @@ -31,7 +31,7 @@ fn main() { // test that borrowing from a box also works let mut b = "hi".to_owned().into_boxed_str(); - let deref!(ref mut s) = b else { unreachable!() }; + let deref!(ref mut s) = b; s.make_ascii_uppercase(); assert_eq!(&*b, "HI"); } diff --git a/tests/ui/pattern/deref-patterns/implicit-cow-deref.rs b/tests/ui/pattern/deref-patterns/implicit-cow-deref.rs index 04c83d4c33f..24770261edc 100644 --- a/tests/ui/pattern/deref-patterns/implicit-cow-deref.rs +++ b/tests/ui/pattern/deref-patterns/implicit-cow-deref.rs @@ -11,7 +11,6 @@ fn main() { match cow { [..] => {} - _ => unreachable!(), } match cow { @@ -22,14 +21,12 @@ fn main() { match Rc::new(&cow) { Cow::Borrowed { 0: _ } => {} Cow::Owned { 0: _ } => unreachable!(), - _ => unreachable!(), } let cow_of_cow: Cow<'_, Cow<'static, [u8]>> = Cow::Owned(cow); match cow_of_cow { [..] => {} - _ => unreachable!(), } // This matches on the outer `Cow` (the owned one). @@ -41,6 +38,5 @@ fn main() { match Rc::new(&cow_of_cow) { Cow::Borrowed { 0: _ } => unreachable!(), Cow::Owned { 0: _ } => {} - _ => unreachable!(), } } |