Auto merge of #136776 - BoxyUwU:forbid_object_lifetime_casts, r=lcnr · rust-lang/rust@198328a (original) (raw)

`@@ -1113,15 +1113,23 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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`self.prove_predicate(

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` ty::ClauseKind::WellFormed(src_ty.into()),

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`);

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`let src_ty = self.normalize(src_ty, location);

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`if let Err(terr) = self.sub_types(

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` src_ty,

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`*ty,

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`) {

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`span_mirbug!(

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`self,

`@@ -1142,7 +1150,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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`self.prove_predicate(

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` ty::ClauseKind::WellFormed(src_ty.into()),

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`);

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`// The type that we see in the fcx is like

`@@ -1155,7 +1167,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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` src_ty,

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`*ty,

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`) {

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`span_mirbug!(

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`self,

`@@ -1184,7 +1200,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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` ty_fn_ptr_from,

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`*ty,

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`) {

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`span_mirbug!(

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`self,

`@@ -1217,7 +1237,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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` ty_fn_ptr_from,

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`*ty,

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`) {

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`span_mirbug!(

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`self,

`@@ -1246,6 +1270,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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` trait_ref,

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` location.to_locations(),

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`ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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` is_implicit_coercion,

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`unsize_to: Some(unsize_to),

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`},

`@@ -1271,7 +1296,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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`*ty_from,

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`*ty_to,

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`) {

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`span_mirbug!(

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`self,

`@@ -1334,7 +1363,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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`*ty_elem,

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`*ty_to,

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` location.to_locations(),

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ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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is_implicit_coercion,

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unsize_to: None,

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`) {

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`span_mirbug!(

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`self,

`@@ -1491,55 +1524,90 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {

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` trait_ref,

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` location.to_locations(),

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`ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: false,

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`is_implicit_coercion: true,

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`unsize_to: None,

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`},

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`);

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} else if let ty::Dynamic(src_tty, _src_lt) =

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} else if let ty::Dynamic(src_tty, src_lt) =

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`*self.struct_tail(src.ty, location).kind()

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` && let ty::Dynamic(dst_tty, dst_lt) =

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`*self.struct_tail(dst.ty, location).kind()

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&& src_tty.principal().is_some()

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&& dst_tty.principal().is_some()

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// This checks (lifetime part of) vtable validity for pointer casts,

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// which is irrelevant when there are aren't principal traits on

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// both sides (aka only auto traits).

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`` -

// Note that other checks (such as denying dyn Send -> `dyn

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`` -

// Debug) are in rustc_hir_typeck`.

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-

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// Remove auto traits.

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`` -

// Auto trait checks are handled in rustc_hir_typeck as FCW.

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let src_obj = Ty::new_dynamic(

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tcx,

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tcx.mk_poly_existential_predicates(

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&src_tty.without_auto_traits().collect::<Vec<_>>(),

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`` -

// FIXME: Once we disallow casting *const dyn Trait + 'short

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`` -

// to *const dyn Trait + 'long, then this can just be src_lt.

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dst_lt,

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);

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let dst_obj = Ty::new_dynamic(

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tcx,

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tcx.mk_poly_existential_predicates(

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&dst_tty.without_auto_traits().collect::<Vec<_>>(),

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match (src_tty.principal(), dst_tty.principal()) {

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(Some(), Some()) => {

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// This checks (lifetime part of) vtable validity for pointer casts,

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// which is irrelevant when there are aren't principal traits on

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// both sides (aka only auto traits).

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`` +

// Note that other checks (such as denying dyn Send -> `dyn

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`` +

// Debug) are in rustc_hir_typeck`.

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+

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// Remove auto traits.

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`` +

// Auto trait checks are handled in rustc_hir_typeck.

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let src_obj = Ty::new_dynamic(

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tcx,

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tcx.mk_poly_existential_predicates(

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&src_tty.without_auto_traits().collect::<Vec<_>>(),

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src_lt,

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);

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let dst_obj = Ty::new_dynamic(

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tcx,

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tcx.mk_poly_existential_predicates(

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&dst_tty.without_auto_traits().collect::<Vec<_>>(),

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dst_lt,

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);

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+

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debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj);

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+

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// Trait parameters are invariant, the only part that actually has

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// subtyping here is the lifetime bound of the dyn-type.

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`` +

// For example in dyn Trait<'a> + 'b <: dyn Trait<'c> + 'd we would

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`` +

// require that 'a == 'c but only that 'b: 'd.

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// We must not allow freely casting lifetime bounds of dyn-types as it

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// may allow for inaccessible VTable methods being callable: #136702

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self.sub_types(

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src_obj,

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dst_obj,

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location.to_locations(),

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ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: true,

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is_implicit_coercion: false,

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unsize_to: None,

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)

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.unwrap();

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}

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(None, None) => {

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// The principalless (no non-auto traits) case:

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`` +

// You can only cast dyn Send + 'long to dyn Send + 'short.

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self.constraints.outlives_constraints.push(

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OutlivesConstraint {

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sup: src_lt.as_var(),

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sub: dst_lt.as_var(),

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locations: location.to_locations(),

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span: location.to_locations().span(self.body),

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category: ConstraintCategory::Cast {

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is_raw_ptr_dyn_type_cast: true,

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is_implicit_coercion: false,

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unsize_to: None,

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variance_info: ty::VarianceDiagInfo::default(),

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from_closure: false,

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);

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}

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(None, Some(_)) => bug!(

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"introducing a principal should have errored in HIR typeck"

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`),

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dst_lt,

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);

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-

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debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj);

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-

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self.sub_types(

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src_obj,

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dst_obj,

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location.to_locations(),

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ConstraintCategory::Cast {

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is_implicit_coercion: false,

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unsize_to: None,

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)

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.unwrap();

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(Some(_), None) => {

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bug!("dropping the principal should have been an unsizing cast")

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}

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}

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`CastKind::Transmute => {