diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs index f1571cf4c8317..fd899425f62d2 100644 --- a/compiler/rustc_hir_typeck/src/coercion.rs +++ b/compiler/rustc_hir_typeck/src/coercion.rs @@ -103,15 +103,6 @@ fn coerce_mutbls<'tcx>( if from_mutbl >= to_mutbl { Ok(()) } else { Err(TypeError::Mutability) } } -/// Do not require any adjustments, i.e. coerce `x -> x`. -fn identity(_: Ty<'_>) -> Vec> { - vec![] -} - -fn simple<'tcx>(kind: Adjust) -> impl FnOnce(Ty<'tcx>) -> Vec> { - move |target| vec![Adjustment { kind, target }] -} - /// This always returns `Ok(...)`. fn success<'tcx>( adj: Vec>, @@ -131,7 +122,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { Coerce { fcx, cause, allow_two_phase, use_lub: false, coerce_never } } - fn unify(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> InferResult<'tcx, Ty<'tcx>> { + fn unify_raw(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> InferResult<'tcx, Ty<'tcx>> { debug!("unify(a: {:?}, b: {:?}, use_lub: {})", a, b, self.use_lub); self.commit_if_ok(|_| { let at = self.at(&self.cause, self.fcx.param_env); @@ -161,13 +152,30 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { }) } + /// Unify two types (using sub or lub). + fn unify(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> CoerceResult<'tcx> { + self.unify_raw(a, b) + .and_then(|InferOk { value: ty, obligations }| success(vec![], ty, obligations)) + } + /// Unify two types (using sub or lub) and produce a specific coercion. - fn unify_and(&self, a: Ty<'tcx>, b: Ty<'tcx>, f: F) -> CoerceResult<'tcx> - where - F: FnOnce(Ty<'tcx>) -> Vec>, - { - self.unify(a, b) - .and_then(|InferOk { value: ty, obligations }| success(f(ty), ty, obligations)) + fn unify_and( + &self, + a: Ty<'tcx>, + b: Ty<'tcx>, + adjustments: impl IntoIterator>, + final_adjustment: Adjust, + ) -> CoerceResult<'tcx> { + self.unify_raw(a, b).and_then(|InferOk { value: ty, obligations }| { + success( + adjustments + .into_iter() + .chain(std::iter::once(Adjustment { target: ty, kind: final_adjustment })) + .collect(), + ty, + obligations, + ) + }) } #[instrument(skip(self))] @@ -180,10 +188,14 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // Coercing from `!` to any type is allowed: if a.is_never() { if self.coerce_never { - return success(simple(Adjust::NeverToAny)(b), b, PredicateObligations::new()); + return success( + vec![Adjustment { kind: Adjust::NeverToAny, target: b }], + b, + PredicateObligations::new(), + ); } else { // Otherwise the only coercion we can do is unification. - return self.unify_and(a, b, identity); + return self.unify(a, b); } } @@ -191,7 +203,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // we have no information about the source type. This will always // ultimately fall back to some form of subtyping. if a.is_ty_var() { - return self.coerce_from_inference_variable(a, b, identity); + return self.coerce_from_inference_variable(a, b); } // Consider coercing the subtype to a DST @@ -247,7 +259,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { ty::FnPtr(a_sig_tys, a_hdr) => { // We permit coercion of fn pointers to drop the // unsafe qualifier. - self.coerce_from_fn_pointer(a, a_sig_tys.with(a_hdr), b) + self.coerce_from_fn_pointer(a_sig_tys.with(a_hdr), b) } ty::Closure(closure_def_id_a, args_a) => { // Non-capturing closures are coercible to @@ -257,7 +269,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { } _ => { // Otherwise, just use unification rules. - self.unify_and(a, b, identity) + self.unify(a, b) } } } @@ -265,12 +277,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { /// Coercing *from* an inference variable. In this case, we have no information /// about the source type, so we can't really do a true coercion and we always /// fall back to subtyping (`unify_and`). - fn coerce_from_inference_variable( - &self, - a: Ty<'tcx>, - b: Ty<'tcx>, - make_adjustments: impl FnOnce(Ty<'tcx>) -> Vec>, - ) -> CoerceResult<'tcx> { + fn coerce_from_inference_variable(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> CoerceResult<'tcx> { debug!("coerce_from_inference_variable(a={:?}, b={:?})", a, b); assert!(a.is_ty_var() && self.shallow_resolve(a) == a); assert!(self.shallow_resolve(b) == b); @@ -298,12 +305,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { "coerce_from_inference_variable: two inference variables, target_ty={:?}, obligations={:?}", target_ty, obligations ); - let adjustments = make_adjustments(target_ty); - InferResult::Ok(InferOk { value: (adjustments, target_ty), obligations }) + success(vec![], target_ty, obligations) } else { // One unresolved type variable: just apply subtyping, we may be able // to do something useful. - self.unify_and(a, b, make_adjustments) + self.unify(a, b) } } @@ -331,7 +337,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { coerce_mutbls(mt_a.mutbl, mutbl_b)?; (r_a, mt_a) } - _ => return self.unify_and(a, b, identity), + _ => return self.unify(a, b), }; let span = self.cause.span; @@ -437,7 +443,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { referent_ty, mutbl_b, // [1] above ); - match self.unify(derefd_ty_a, b) { + match self.unify_raw(derefd_ty_a, b) { Ok(ok) => { found = Some(ok); break; @@ -579,13 +585,13 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // We only have the latter, so we use an inference variable // for the former and let type inference do the rest. let coerce_target = self.next_ty_var(self.cause.span); - let mut coercion = self.unify_and(coerce_target, target, |target| { - let unsize = Adjustment { kind: Adjust::Pointer(PointerCoercion::Unsize), target }; - match reborrow { - None => vec![unsize], - Some((ref deref, ref autoref)) => vec![deref.clone(), autoref.clone(), unsize], - } - })?; + + let mut coercion = self.unify_and( + coerce_target, + target, + reborrow.into_iter().flat_map(|(deref, autoref)| [deref, autoref]), + Adjust::Pointer(PointerCoercion::Unsize), + )?; let mut selcx = traits::SelectionContext::new(self); @@ -708,7 +714,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { && let ty::Dynamic(b_data, _, ty::DynStar) = b.kind() && a_data.principal_def_id() == b_data.principal_def_id() { - return self.unify_and(a, b, |_| vec![]); + return self.unify(a, b); } // Check the obligations of the cast -- for example, when casting @@ -808,23 +814,15 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // To complete the reborrow, we need to make sure we can unify the inner types, and if so we // add the adjustments. - self.unify_and(a, b, |_inner_ty| { - vec![Adjustment { kind: Adjust::ReborrowPin(mut_b), target: b }] - }) + self.unify_and(a, b, [], Adjust::ReborrowPin(mut_b)) } - fn coerce_from_safe_fn( + fn coerce_from_safe_fn( &self, - a: Ty<'tcx>, fn_ty_a: ty::PolyFnSig<'tcx>, b: Ty<'tcx>, - to_unsafe: F, - normal: G, - ) -> CoerceResult<'tcx> - where - F: FnOnce(Ty<'tcx>) -> Vec>, - G: FnOnce(Ty<'tcx>) -> Vec>, - { + adjustment: Option, + ) -> CoerceResult<'tcx> { self.commit_if_ok(|snapshot| { let outer_universe = self.infcx.universe(); @@ -833,9 +831,19 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { && hdr_b.safety.is_unsafe() { let unsafe_a = self.tcx.safe_to_unsafe_fn_ty(fn_ty_a); - self.unify_and(unsafe_a, b, to_unsafe) + self.unify_and( + unsafe_a, + b, + adjustment + .map(|kind| Adjustment { kind, target: Ty::new_fn_ptr(self.tcx, fn_ty_a) }), + Adjust::Pointer(PointerCoercion::UnsafeFnPointer), + ) } else { - self.unify_and(a, b, normal) + let a = Ty::new_fn_ptr(self.tcx, fn_ty_a); + match adjustment { + Some(adjust) => self.unify_and(a, b, [], adjust), + None => self.unify(a, b), + } }; // FIXME(#73154): This is a hack. Currently LUB can generate @@ -852,7 +860,6 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { fn coerce_from_fn_pointer( &self, - a: Ty<'tcx>, fn_ty_a: ty::PolyFnSig<'tcx>, b: Ty<'tcx>, ) -> CoerceResult<'tcx> { @@ -861,15 +868,9 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { //! let b = self.shallow_resolve(b); - debug!("coerce_from_fn_pointer(a={:?}, b={:?})", a, b); - - self.coerce_from_safe_fn( - a, - fn_ty_a, - b, - simple(Adjust::Pointer(PointerCoercion::UnsafeFnPointer)), - identity, - ) + debug!(?fn_ty_a, ?b, "coerce_from_fn_pointer"); + + self.coerce_from_safe_fn(fn_ty_a, b, None) } fn coerce_from_fn_item(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> CoerceResult<'tcx> { @@ -916,30 +917,16 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { self.at(&self.cause, self.param_env).normalize(a_sig); obligations.extend(o1); - let a_fn_pointer = Ty::new_fn_ptr(self.tcx, a_sig); let InferOk { value, obligations: o2 } = self.coerce_from_safe_fn( - a_fn_pointer, a_sig, b, - |unsafe_ty| { - vec![ - Adjustment { - kind: Adjust::Pointer(PointerCoercion::ReifyFnPointer), - target: a_fn_pointer, - }, - Adjustment { - kind: Adjust::Pointer(PointerCoercion::UnsafeFnPointer), - target: unsafe_ty, - }, - ] - }, - simple(Adjust::Pointer(PointerCoercion::ReifyFnPointer)), + Some(Adjust::Pointer(PointerCoercion::ReifyFnPointer)), )?; obligations.extend(o2); Ok(InferOk { value, obligations }) } - _ => self.unify_and(a, b, identity), + _ => self.unify(a, b), } } @@ -983,10 +970,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { self.unify_and( pointer_ty, b, - simple(Adjust::Pointer(PointerCoercion::ClosureFnPointer(safety))), + [], + Adjust::Pointer(PointerCoercion::ClosureFnPointer(safety)), ) } - _ => self.unify_and(a, b, identity), + _ => self.unify(a, b), } } @@ -1001,7 +989,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { let (is_ref, mt_a) = match *a.kind() { ty::Ref(_, ty, mutbl) => (true, ty::TypeAndMut { ty, mutbl }), ty::RawPtr(ty, mutbl) => (false, ty::TypeAndMut { ty, mutbl }), - _ => return self.unify_and(a, b, identity), + _ => return self.unify(a, b), }; coerce_mutbls(mt_a.mutbl, mutbl_b)?; @@ -1011,16 +999,16 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // representation, we still register an Adjust::DerefRef so that // regionck knows that the region for `a` must be valid here. if is_ref { - self.unify_and(a_raw, b, |target| { - vec![ - Adjustment { kind: Adjust::Deref(None), target: mt_a.ty }, - Adjustment { kind: Adjust::Borrow(AutoBorrow::RawPtr(mutbl_b)), target }, - ] - }) + self.unify_and( + a_raw, + b, + [Adjustment { kind: Adjust::Deref(None), target: mt_a.ty }], + Adjust::Borrow(AutoBorrow::RawPtr(mutbl_b)), + ) } else if mt_a.mutbl != mutbl_b { - self.unify_and(a_raw, b, simple(Adjust::Pointer(PointerCoercion::MutToConstPointer))) + self.unify_and(a_raw, b, [], Adjust::Pointer(PointerCoercion::MutToConstPointer)) } else { - self.unify_and(a_raw, b, identity) + self.unify(a_raw, b) } } } @@ -1118,9 +1106,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { let cause = self.cause(DUMMY_SP, ObligationCauseCode::ExprAssignable); // We don't ever need two-phase here since we throw out the result of the coercion. let coerce = Coerce::new(self, cause, AllowTwoPhase::No, true); - coerce - .autoderef(DUMMY_SP, expr_ty) - .find_map(|(ty, steps)| self.probe(|_| coerce.unify(ty, target)).ok().map(|_| steps)) + coerce.autoderef(DUMMY_SP, expr_ty).find_map(|(ty, steps)| { + self.probe(|_| coerce.unify_raw(ty, target)).ok().map(|_| steps) + }) } /// Given a type, this function will calculate and return the type given