diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs index c19d8cf6dc5..11ed7db9eb7 100644 --- a/compiler/rustc_hir_typeck/src/pat.rs +++ b/compiler/rustc_hir_typeck/src/pat.rs @@ -162,12 +162,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { /// Mode for adjusting the expected type and binding mode. #[derive(Clone, Copy, Debug, PartialEq, Eq)] enum AdjustMode { - /// Peel off all immediate reference types. - Peel, + /// Peel off all immediate reference types. If the `deref_patterns` feature is enabled, this + /// also peels smart pointer ADTs. + Peel { kind: PeelKind }, /// Pass on the input binding mode and expected type. Pass, } +/// Restrictions on what types to peel when adjusting the expected type and binding mode. +#[derive(Clone, Copy, Debug, PartialEq, Eq)] +enum PeelKind { + /// Only peel reference types. This is used for explicit `deref!(_)` patterns, which dereference + /// any number of `&`/`&mut` references, plus a single smart pointer. + ExplicitDerefPat, + /// Implicitly peel any number of references, and if `deref_patterns` is enabled, smart pointer + /// ADTs. In order to peel only as much as necessary for the pattern to match, the `until_adt` + /// field contains the ADT def that the pattern is a constructor for, if applicable, so that we + /// don't peel it. See [`ResolvedPat`] for more information. + // TODO: add `ResolvedPat` and `until_adt`. + Implicit, +} + /// `ref mut` bindings (explicit or match-ergonomics) are not allowed behind an `&` reference. /// Normally, the borrow checker enforces this, but for (currently experimental) match ergonomics, /// we track this when typing patterns for two purposes: @@ -390,7 +405,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } // Resolve type if needed. - let expected = if let AdjustMode::Peel = adjust_mode + let expected = if let AdjustMode::Peel { .. } = adjust_mode && pat.default_binding_modes { self.try_structurally_resolve_type(pat.span, expected) @@ -403,7 +418,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { match pat.kind { // Peel off a `&` or `&mut` from the scrutinee type. See the examples in // `tests/ui/rfcs/rfc-2005-default-binding-mode`. - _ if let AdjustMode::Peel = adjust_mode + _ if let AdjustMode::Peel { .. } = adjust_mode && pat.default_binding_modes && let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind() => { @@ -443,6 +458,45 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // Recurse with the new expected type. self.check_pat_inner(pat, opt_path_res, adjust_mode, inner_ty, new_pat_info) } + // If `deref_patterns` is enabled, peel a smart pointer from the scrutinee type. See the + // examples in `tests/ui/pattern/deref_patterns/`. + _ if self.tcx.features().deref_patterns() + && let AdjustMode::Peel { kind: PeelKind::Implicit } = adjust_mode + && pat.default_binding_modes + // For simplicity, only apply overloaded derefs if `expected` is a known ADT. + // FIXME(deref_patterns): we'll get better diagnostics for users trying to + // implicitly deref generics if we allow them here, but primitives, tuples, and + // inference vars definitely should be stopped. Figure out what makes most sense. + // TODO: stop peeling if the pattern is a constructor for the scrutinee type + && expected.is_adt() + // At this point, the pattern isn't able to match `expected` without peeling. Check + // that it implements `Deref` before assuming it's a smart pointer, to get a normal + // type error instead of a missing impl error if not. This only checks for `Deref`, + // not `DerefPure`: we require that too, but we want a trait error if it's missing. + && let Some(deref_trait) = self.tcx.lang_items().deref_trait() + && self + .type_implements_trait(deref_trait, [expected], self.param_env) + .may_apply() => + { + debug!("scrutinee ty {expected:?} is a smart pointer, inserting overloaded deref"); + // The scrutinee is a smart pointer; implicitly dereference it. This adds a + // requirement that `expected: DerefPure`. + let inner_ty = self.deref_pat_target(pat.span, expected); + // Once we've checked `pat`, we'll add a `DerefMut` bound if it contains any + // `ref mut` bindings. TODO: implement that, then reference here. + + // Preserve the smart pointer type for THIR lowering and upvar analysis. + self.typeck_results + .borrow_mut() + .pat_adjustments_mut() + .entry(pat.hir_id) + .or_default() + .push(PatAdjustment { kind: PatAdjust::OverloadedDeref, source: expected }); + + // Recurse, using the old pat info to keep `current_depth` to its old value. + // Peeling smart pointers does not update the default binding mode. + self.check_pat_inner(pat, opt_path_res, adjust_mode, inner_ty, old_pat_info) + } PatKind::Missing | PatKind::Wild | PatKind::Err(_) => expected, // We allow any type here; we ensure that the type is uninhabited during match checking. PatKind::Never => expected, @@ -505,12 +559,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { PatKind::Struct(..) | PatKind::TupleStruct(..) | PatKind::Tuple(..) - | PatKind::Box(_) - | PatKind::Deref(_) | PatKind::Range(..) - | PatKind::Slice(..) => AdjustMode::Peel, + | PatKind::Slice(..) => AdjustMode::Peel { kind: PeelKind::Implicit }, + // When checking an explicit deref pattern, only peel reference types. + // FIXME(deref_patterns): If box patterns and deref patterns need to coexist, box + // patterns may want `PeelKind::Implicit`, stopping on encountering a box. + | PatKind::Box(_) + | PatKind::Deref(_) => AdjustMode::Peel { kind: PeelKind::ExplicitDerefPat }, // A never pattern behaves somewhat like a literal or unit variant. - PatKind::Never => AdjustMode::Peel, + PatKind::Never => AdjustMode::Peel { kind: PeelKind::Implicit }, PatKind::Expr(PatExpr { kind: PatExprKind::Path(_), .. }) => match opt_path_res.unwrap() { // These constants can be of a reference type, e.g. `const X: &u8 = &0;`. // Peeling the reference types too early will cause type checking failures. @@ -520,7 +577,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // could successfully compile. The former being `Self` requires a unit struct. // In either case, and unlike constants, the pattern itself cannot be // a reference type wherefore peeling doesn't give up any expressiveness. - _ => AdjustMode::Peel, + _ => AdjustMode::Peel { kind: PeelKind::Implicit }, }, // String and byte-string literals result in types `&str` and `&[u8]` respectively. @@ -530,7 +587,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // Call `resolve_vars_if_possible` here for inline const blocks. PatKind::Expr(lt) => match self.resolve_vars_if_possible(self.check_pat_expr_unadjusted(lt)).kind() { ty::Ref(..) => AdjustMode::Pass, - _ => AdjustMode::Peel, + _ => AdjustMode::Peel { kind: PeelKind::Implicit }, }, // Ref patterns are complicated, we handle them in `check_pat_ref`. @@ -2256,31 +2313,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { expected: Ty<'tcx>, pat_info: PatInfo<'tcx>, ) -> Ty<'tcx> { - let tcx = self.tcx; - // Register a `DerefPure` bound, which is required by all `deref!()` pats. - self.register_bound( - expected, - tcx.require_lang_item(hir::LangItem::DerefPure, Some(span)), - self.misc(span), - ); - // ::Target - let ty = Ty::new_projection( - tcx, - tcx.require_lang_item(hir::LangItem::DerefTarget, Some(span)), - [expected], - ); - let ty = self.normalize(span, ty); - let ty = self.try_structurally_resolve_type(span, ty); - self.check_pat(inner, ty, pat_info); + let target_ty = self.deref_pat_target(span, expected); + self.check_pat(inner, target_ty, pat_info); // Check if the pattern has any `ref mut` bindings, which would require // `DerefMut` to be emitted in MIR building instead of just `Deref`. // We do this *after* checking the inner pattern, since we want to make // sure to apply any match-ergonomics adjustments. + // TODO: move this to a separate definition to share it with implicit deref pats if self.typeck_results.borrow().pat_has_ref_mut_binding(inner) { self.register_bound( expected, - tcx.require_lang_item(hir::LangItem::DerefMut, Some(span)), + self.tcx.require_lang_item(hir::LangItem::DerefMut, Some(span)), self.misc(span), ); } @@ -2288,6 +2332,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { expected } + fn deref_pat_target(&self, span: Span, source_ty: Ty<'tcx>) -> Ty<'tcx> { + // Register a `DerefPure` bound, which is required by all `deref!()` pats. + let tcx = self.tcx; + self.register_bound( + source_ty, + tcx.require_lang_item(hir::LangItem::DerefPure, Some(span)), + self.misc(span), + ); + // The expected type for the deref pat's inner pattern is `::Target`. + let target_ty = Ty::new_projection( + tcx, + tcx.require_lang_item(hir::LangItem::DerefTarget, Some(span)), + [source_ty], + ); + let target_ty = self.normalize(span, target_ty); + self.try_structurally_resolve_type(span, target_ty) + } + // Precondition: Pat is Ref(inner) fn check_pat_ref( &self, diff --git a/tests/ui/pattern/deref-patterns/bindings.rs b/tests/ui/pattern/deref-patterns/bindings.rs index 5881e4166a4..ce10cd5439e 100644 --- a/tests/ui/pattern/deref-patterns/bindings.rs +++ b/tests/ui/pattern/deref-patterns/bindings.rs @@ -1,7 +1,9 @@ +//@ revisions: explicit implicit //@ run-pass #![feature(deref_patterns)] #![allow(incomplete_features)] +#[cfg(explicit)] fn simple_vec(vec: Vec) -> u32 { match vec { deref!([]) => 100, @@ -13,6 +15,19 @@ fn simple_vec(vec: Vec) -> u32 { } } +#[cfg(implicit)] +fn simple_vec(vec: Vec) -> u32 { + match vec { + [] => 100, + [x] if x == 4 => x + 4, + [x] => x, + [1, x] => x + 200, + deref!(ref slice) => slice.iter().sum(), + _ => 2000, + } +} + +#[cfg(explicit)] fn nested_vec(vecvec: Vec>) -> u32 { match vecvec { deref!([]) => 0, @@ -24,6 +39,18 @@ fn nested_vec(vecvec: Vec>) -> u32 { } } +#[cfg(implicit)] +fn nested_vec(vecvec: Vec>) -> u32 { + match vecvec { + [] => 0, + [[x]] => x, + [[0, x] | [1, x]] => x, + [ref x] => x.iter().sum(), + [[], [1, x, y]] => y - x, + _ => 2000, + } +} + fn ref_mut(val: u32) -> u32 { let mut b = Box::new(0u32); match &mut b { diff --git a/tests/ui/pattern/deref-patterns/branch.rs b/tests/ui/pattern/deref-patterns/branch.rs index 1bac1006d9d..9d72b35fd2f 100644 --- a/tests/ui/pattern/deref-patterns/branch.rs +++ b/tests/ui/pattern/deref-patterns/branch.rs @@ -1,8 +1,10 @@ +//@ revisions: explicit implicit //@ run-pass // Test the execution of deref patterns. #![feature(deref_patterns)] #![allow(incomplete_features)] +#[cfg(explicit)] fn branch(vec: Vec) -> u32 { match vec { deref!([]) => 0, @@ -12,6 +14,17 @@ fn branch(vec: Vec) -> u32 { } } +#[cfg(implicit)] +fn branch(vec: Vec) -> u32 { + match vec { + [] => 0, + [1, _, 3] => 1, + [2, ..] => 2, + _ => 1000, + } +} + +#[cfg(explicit)] fn nested(vec: Vec>) -> u32 { match vec { deref!([deref!([]), ..]) => 1, @@ -20,6 +33,15 @@ fn nested(vec: Vec>) -> u32 { } } +#[cfg(implicit)] +fn nested(vec: Vec>) -> u32 { + match vec { + [[], ..] => 1, + [[0, ..], [1, ..]] => 2, + _ => 1000, + } +} + fn main() { assert!(matches!(Vec::::new(), deref!([]))); assert!(matches!(vec![1], deref!([1]))); diff --git a/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.rs b/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.rs index 84b5ec09dc7..791776be5ac 100644 --- a/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.rs +++ b/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.rs @@ -21,4 +21,22 @@ fn cant_move_out_rc(rc: Rc) -> Struct { } } +struct Container(Struct); + +fn cant_move_out_box_implicit(b: Box) -> Struct { + match b { + //~^ ERROR: cannot move out of a shared reference + Container(x) => x, + _ => unreachable!(), + } +} + +fn cant_move_out_rc_implicit(rc: Rc) -> Struct { + match rc { + //~^ ERROR: cannot move out of a shared reference + Container(x) => x, + _ => unreachable!(), + } +} + fn main() {} diff --git a/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.stderr b/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.stderr index 2cf435b1179..1887800fc38 100644 --- a/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.stderr +++ b/tests/ui/pattern/deref-patterns/cant_move_out_of_pattern.stderr @@ -32,6 +32,40 @@ help: consider borrowing the pattern binding LL | deref!(ref x) => x, | +++ -error: aborting due to 2 previous errors +error[E0507]: cannot move out of a shared reference + --> $DIR/cant_move_out_of_pattern.rs:27:11 + | +LL | match b { + | ^ +LL | +LL | Container(x) => x, + | - + | | + | data moved here + | move occurs because `x` has type `Struct`, which does not implement the `Copy` trait + | +help: consider borrowing the pattern binding + | +LL | Container(ref x) => x, + | +++ + +error[E0507]: cannot move out of a shared reference + --> $DIR/cant_move_out_of_pattern.rs:35:11 + | +LL | match rc { + | ^^ +LL | +LL | Container(x) => x, + | - + | | + | data moved here + | move occurs because `x` has type `Struct`, which does not implement the `Copy` trait + | +help: consider borrowing the pattern binding + | +LL | Container(ref x) => x, + | +++ + +error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0507`. diff --git a/tests/ui/pattern/deref-patterns/typeck.rs b/tests/ui/pattern/deref-patterns/typeck.rs index f23f7042cd8..3a7ce9d1deb 100644 --- a/tests/ui/pattern/deref-patterns/typeck.rs +++ b/tests/ui/pattern/deref-patterns/typeck.rs @@ -10,26 +10,32 @@ fn main() { let vec: Vec = Vec::new(); match vec { deref!([..]) => {} + [..] => {} _ => {} } match Box::new(true) { deref!(true) => {} + true => {} _ => {} } match &Box::new(true) { deref!(true) => {} + true => {} _ => {} } match &Rc::new(0) { deref!(1..) => {} + 1.. => {} _ => {} } let _: &Struct = match &Rc::new(Struct) { deref!(x) => x, + Struct => &Struct, _ => unreachable!(), }; let _: &[Struct] = match &Rc::new(vec![Struct]) { deref!(deref!(x)) => x, + [Struct] => &[Struct], _ => unreachable!(), }; } diff --git a/tests/ui/pattern/deref-patterns/typeck_fail.rs b/tests/ui/pattern/deref-patterns/typeck_fail.rs index 040118449ec..4b9ad7d25f0 100644 --- a/tests/ui/pattern/deref-patterns/typeck_fail.rs +++ b/tests/ui/pattern/deref-patterns/typeck_fail.rs @@ -7,11 +7,22 @@ fn main() { match "foo".to_string() { deref!("foo") => {} //~^ ERROR: mismatched types + "foo" => {} + //~^ ERROR: mismatched types _ => {} } match &"foo".to_string() { deref!("foo") => {} //~^ ERROR: mismatched types + "foo" => {} + //~^ ERROR: mismatched types + _ => {} + } + + // Make sure we don't try implicitly dereferncing any ADT. + match Some(0) { + Ok(0) => {} + //~^ ERROR: mismatched types _ => {} } } diff --git a/tests/ui/pattern/deref-patterns/typeck_fail.stderr b/tests/ui/pattern/deref-patterns/typeck_fail.stderr index 1c14802745a..3e2f3561882 100644 --- a/tests/ui/pattern/deref-patterns/typeck_fail.stderr +++ b/tests/ui/pattern/deref-patterns/typeck_fail.stderr @@ -7,13 +7,45 @@ LL | deref!("foo") => {} | ^^^^^ expected `str`, found `&str` error[E0308]: mismatched types - --> $DIR/typeck_fail.rs:13:16 + --> $DIR/typeck_fail.rs:10:9 + | +LL | match "foo".to_string() { + | ----------------- this expression has type `String` +... +LL | "foo" => {} + | ^^^^^ expected `String`, found `&str` + +error[E0308]: mismatched types + --> $DIR/typeck_fail.rs:15:16 | LL | match &"foo".to_string() { | ------------------ this expression has type `&String` LL | deref!("foo") => {} | ^^^^^ expected `str`, found `&str` -error: aborting due to 2 previous errors +error[E0308]: mismatched types + --> $DIR/typeck_fail.rs:17:9 + | +LL | match &"foo".to_string() { + | ------------------ this expression has type `&String` +... +LL | "foo" => {} + | ^^^^^ expected `&String`, found `&str` + | + = note: expected reference `&String` + found reference `&'static str` + +error[E0308]: mismatched types + --> $DIR/typeck_fail.rs:24:9 + | +LL | match Some(0) { + | ------- this expression has type `Option<{integer}>` +LL | Ok(0) => {} + | ^^^^^ expected `Option<{integer}>`, found `Result<_, _>` + | + = note: expected enum `Option<{integer}>` + found enum `Result<_, _>` + +error: aborting due to 5 previous errors For more information about this error, try `rustc --explain E0308`. diff --git a/tests/ui/pattern/deref-patterns/unsatisfied-bounds.rs b/tests/ui/pattern/deref-patterns/unsatisfied-bounds.rs new file mode 100644 index 00000000000..00064b2320c --- /dev/null +++ b/tests/ui/pattern/deref-patterns/unsatisfied-bounds.rs @@ -0,0 +1,21 @@ +#![feature(deref_patterns)] +#![allow(incomplete_features)] + +struct MyPointer; + +impl std::ops::Deref for MyPointer { + type Target = (); + fn deref(&self) -> &() { + &() + } +} + +fn main() { + // Test that we get a trait error if a user attempts implicit deref pats on their own impls. + // FIXME(deref_patterns): there should be a special diagnostic for missing `DerefPure`. + match MyPointer { + () => {} + //~^ the trait bound `MyPointer: DerefPure` is not satisfied + _ => {} + } +} diff --git a/tests/ui/pattern/deref-patterns/unsatisfied-bounds.stderr b/tests/ui/pattern/deref-patterns/unsatisfied-bounds.stderr new file mode 100644 index 00000000000..983ce27865c --- /dev/null +++ b/tests/ui/pattern/deref-patterns/unsatisfied-bounds.stderr @@ -0,0 +1,9 @@ +error[E0277]: the trait bound `MyPointer: DerefPure` is not satisfied + --> $DIR/unsatisfied-bounds.rs:17:9 + | +LL | () => {} + | ^^ the trait `DerefPure` is not implemented for `MyPointer` + +error: aborting due to 1 previous error + +For more information about this error, try `rustc --explain E0277`.