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Allow patterns to constrain the hidden type of opaque types #99806

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Sep 20, 2022
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4 changes: 3 additions & 1 deletion compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
Original file line number Diff line number Diff line change
@@ -2146,7 +2146,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
StorageDeadOrDrop::Destructor(_) => kind,
},
ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => {
ProjectionElem::OpaqueCast { .. }
| ProjectionElem::Field(..)
| ProjectionElem::Downcast(..) => {
match place_ty.ty.kind() {
ty::Adt(def, _) if def.has_dtor(tcx) => {
// Report the outermost adt with a destructor
2 changes: 2 additions & 0 deletions compiler/rustc_borrowck/src/diagnostics/mod.rs
Original file line number Diff line number Diff line change
@@ -237,6 +237,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
ProjectionElem::Downcast(..) if opt.including_downcast => return None,
ProjectionElem::Downcast(..) => (),
ProjectionElem::OpaqueCast(..) => (),
ProjectionElem::Field(field, _ty) => {
// FIXME(project-rfc_2229#36): print capture precisely here.
if let Some(field) = self.is_upvar_field_projection(PlaceRef {
@@ -317,6 +318,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
}
ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
},
};
Original file line number Diff line number Diff line change
@@ -169,6 +169,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
..,
ProjectionElem::Index(_)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::OpaqueCast { .. }
| ProjectionElem::Subslice { .. }
| ProjectionElem::Downcast(..),
],
2 changes: 2 additions & 0 deletions compiler/rustc_borrowck/src/lib.rs
Original file line number Diff line number Diff line change
@@ -1781,6 +1781,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
for (place_base, elem) in place.iter_projections().rev() {
match elem {
ProjectionElem::Index(_/*operand*/) |
ProjectionElem::OpaqueCast(_) |
ProjectionElem::ConstantIndex { .. } |
// assigning to P[i] requires P to be valid.
ProjectionElem::Downcast(_/*adt_def*/, _/*variant_idx*/) =>
@@ -2172,6 +2173,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
| ProjectionElem::Index(..)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. }
| ProjectionElem::OpaqueCast { .. }
| ProjectionElem::Downcast(..) => {
let upvar_field_projection = self.is_upvar_field_projection(place);
if let Some(field) = upvar_field_projection {
13 changes: 13 additions & 0 deletions compiler/rustc_borrowck/src/places_conflict.rs
Original file line number Diff line number Diff line change
@@ -250,6 +250,7 @@ fn place_components_conflict<'tcx>(
| (ProjectionElem::Index { .. }, _, _)
| (ProjectionElem::ConstantIndex { .. }, _, _)
| (ProjectionElem::Subslice { .. }, _, _)
| (ProjectionElem::OpaqueCast { .. }, _, _)
| (ProjectionElem::Downcast { .. }, _, _) => {
// Recursive case. This can still be disjoint on a
// further iteration if this a shallow access and
@@ -317,6 +318,17 @@ fn place_projection_conflict<'tcx>(
debug!("place_element_conflict: DISJOINT-OR-EQ-DEREF");
Overlap::EqualOrDisjoint
}
(ProjectionElem::OpaqueCast(v1), ProjectionElem::OpaqueCast(v2)) => {
if v1 == v2 {
// same type - recur.
debug!("place_element_conflict: DISJOINT-OR-EQ-OPAQUE");
Overlap::EqualOrDisjoint
} else {
// Different types. Disjoint!
debug!("place_element_conflict: DISJOINT-OPAQUE");
Overlap::Disjoint
}
}
(ProjectionElem::Field(f1, _), ProjectionElem::Field(f2, _)) => {
if f1 == f2 {
// same field (e.g., `a.y` vs. `a.y`) - recur.
@@ -520,6 +532,7 @@ fn place_projection_conflict<'tcx>(
| ProjectionElem::Field(..)
| ProjectionElem::Index(..)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::OpaqueCast { .. }
| ProjectionElem::Subslice { .. }
| ProjectionElem::Downcast(..),
_,
1 change: 1 addition & 0 deletions compiler/rustc_borrowck/src/prefixes.rs
Original file line number Diff line number Diff line change
@@ -81,6 +81,7 @@ impl<'cx, 'tcx> Iterator for Prefixes<'cx, 'tcx> {
}
ProjectionElem::Downcast(..)
| ProjectionElem::Subslice { .. }
| ProjectionElem::OpaqueCast { .. }
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Index(_) => {
cursor = cursor_base;
17 changes: 16 additions & 1 deletion compiler/rustc_borrowck/src/type_check/mod.rs
Original file line number Diff line number Diff line change
@@ -760,6 +760,19 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
}
PlaceTy::from_ty(fty)
}
ProjectionElem::OpaqueCast(ty) => {
let ty = self.sanitize_type(place, ty);
let ty = self.cx.normalize(ty, location);
self.cx
.eq_types(
base.ty,
ty,
location.to_locations(),
ConstraintCategory::TypeAnnotation,
)
.unwrap();
PlaceTy::from_ty(ty)
}
}
}

@@ -1166,10 +1179,11 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
tcx,
self.param_env,
proj,
|this, field, ()| {
|this, field, _| {
let ty = this.field_ty(tcx, field);
self.normalize(ty, locations)
},
|_, _| unreachable!(),
);
curr_projected_ty = projected_ty;
}
@@ -2501,6 +2515,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
}
ProjectionElem::Field(..)
| ProjectionElem::Downcast(..)
| ProjectionElem::OpaqueCast(..)
| ProjectionElem::Index(..)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. } => {
1 change: 1 addition & 0 deletions compiler/rustc_codegen_cranelift/src/base.rs
Original file line number Diff line number Diff line change
@@ -850,6 +850,7 @@ pub(crate) fn codegen_place<'tcx>(
PlaceElem::Deref => {
cplace = cplace.place_deref(fx);
}
PlaceElem::OpaqueCast(ty) => cplace = cplace.place_opaque_cast(fx, ty),
PlaceElem::Field(field, _ty) => {
cplace = cplace.place_field(fx, field);
}
8 changes: 8 additions & 0 deletions compiler/rustc_codegen_cranelift/src/value_and_place.rs
Original file line number Diff line number Diff line change
@@ -621,6 +621,14 @@ impl<'tcx> CPlace<'tcx> {
}
}

pub(crate) fn place_opaque_cast(
self,
fx: &mut FunctionCx<'_, '_, 'tcx>,
ty: Ty<'tcx>,
) -> CPlace<'tcx> {
CPlace { inner: self.inner, layout: fx.layout_of(ty) }
}

pub(crate) fn place_field(
self,
fx: &mut FunctionCx<'_, '_, 'tcx>,
16 changes: 16 additions & 0 deletions compiler/rustc_codegen_ssa/src/mir/place.rs
Original file line number Diff line number Diff line change
@@ -400,6 +400,21 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
downcast
}

pub fn project_type<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
&self,
bx: &mut Bx,
ty: Ty<'tcx>,
) -> Self {
let mut downcast = *self;
downcast.layout = bx.cx().layout_of(ty);

// Cast to the appropriate type.
let variant_ty = bx.cx().backend_type(downcast.layout);
downcast.llval = bx.pointercast(downcast.llval, bx.cx().type_ptr_to(variant_ty));

downcast
}

pub fn storage_live<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) {
bx.lifetime_start(self.llval, self.layout.size);
}
@@ -442,6 +457,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mir::ProjectionElem::Field(ref field, _) => {
cg_base.project_field(bx, field.index())
}
mir::ProjectionElem::OpaqueCast(ty) => cg_base.project_type(bx, ty),
mir::ProjectionElem::Index(index) => {
let index = &mir::Operand::Copy(mir::Place::from(index));
let index = self.codegen_operand(bx, index);
10 changes: 10 additions & 0 deletions compiler/rustc_const_eval/src/interpret/projection.rs
Original file line number Diff line number Diff line change
@@ -350,6 +350,11 @@ where
) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
use rustc_middle::mir::ProjectionElem::*;
Ok(match proj_elem {
OpaqueCast(ty) => {
let mut place = base.clone();
place.layout = self.layout_of(ty)?;
place
}
Field(field, _) => self.place_field(base, field.index())?,
Downcast(_, variant) => self.place_downcast(base, variant)?,
Deref => self.deref_operand(&self.place_to_op(base)?)?.into(),
@@ -374,6 +379,11 @@ where
) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
use rustc_middle::mir::ProjectionElem::*;
Ok(match proj_elem {
OpaqueCast(ty) => {
let mut op = base.clone();
op.layout = self.layout_of(ty)?;
op
}
Field(field, _) => self.operand_field(base, field.index())?,
Downcast(_, variant) => self.operand_downcast(base, variant)?,
Deref => self.deref_operand(base)?.into(),
Original file line number Diff line number Diff line change
@@ -656,6 +656,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {

ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Downcast(..)
| ProjectionElem::OpaqueCast(..)
| ProjectionElem::Subslice { .. }
| ProjectionElem::Field(..)
| ProjectionElem::Index(_) => {}
Original file line number Diff line number Diff line change
@@ -308,6 +308,7 @@ where

ProjectionElem::Deref
| ProjectionElem::Field(_, _)
| ProjectionElem::OpaqueCast(_)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. }
| ProjectionElem::Downcast(_, _)
2 changes: 1 addition & 1 deletion compiler/rustc_const_eval/src/transform/promote_consts.rs
Original file line number Diff line number Diff line change
@@ -361,7 +361,7 @@ impl<'tcx> Validator<'_, 'tcx> {
return Err(Unpromotable);
}
}
ProjectionElem::Downcast(..) => {
ProjectionElem::OpaqueCast(..) | ProjectionElem::Downcast(..) => {
return Err(Unpromotable);
}

8 changes: 7 additions & 1 deletion compiler/rustc_middle/src/mir/mod.rs
Original file line number Diff line number Diff line change
@@ -1380,6 +1380,7 @@ impl<V, T> ProjectionElem<V, T> {

Self::Field(_, _)
| Self::Index(_)
| Self::OpaqueCast(_)
| Self::ConstantIndex { .. }
| Self::Subslice { .. }
| Self::Downcast(_, _) => false,
@@ -1574,7 +1575,9 @@ impl Debug for Place<'_> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
for elem in self.projection.iter().rev() {
match elem {
ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
ProjectionElem::OpaqueCast(_)
| ProjectionElem::Downcast(_, _)
| ProjectionElem::Field(_, _) => {
write!(fmt, "(").unwrap();
}
ProjectionElem::Deref => {
@@ -1590,6 +1593,9 @@ impl Debug for Place<'_> {

for elem in self.projection.iter() {
match elem {
ProjectionElem::OpaqueCast(ty) => {
write!(fmt, " as {})", ty)?;
}
ProjectionElem::Downcast(Some(name), _index) => {
write!(fmt, " as {})", name)?;
}
7 changes: 7 additions & 0 deletions compiler/rustc_middle/src/mir/syntax.rs
Original file line number Diff line number Diff line change
@@ -829,6 +829,9 @@ pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
/// generator has more than one variant, the parent place's variant index must be set, indicating
/// which variant is being used. If it has just one variant, the variant index may or may not be
/// included - the single possible variant is inferred if it is not included.
/// - [`OpaqueCast`](ProjectionElem::OpaqueCast): This projection changes the place's type to the
/// given one, and makes no other changes. A `OpaqueCast` projection on any type other than an
/// opaque type from the current crate is not well-formed.
/// - [`ConstantIndex`](ProjectionElem::ConstantIndex): Computes an offset in units of `T` into the
/// place as described in the documentation for the `ProjectionElem`. The resulting address is
/// the parent's address plus that offset, and the type is `T`. This is only legal if the parent
@@ -928,6 +931,10 @@ pub enum ProjectionElem<V, T> {
///
/// The included Symbol is the name of the variant, used for printing MIR.
Downcast(Option<Symbol>, VariantIdx),

/// Like an explicit cast from an opaque type to a concrete type, but without
/// requiring an intermediate variable.
OpaqueCast(T),
}

/// Alias for projections as they appear in places, where the base is a place
4 changes: 3 additions & 1 deletion compiler/rustc_middle/src/mir/tcx.rs
Original file line number Diff line number Diff line change
@@ -57,7 +57,7 @@ impl<'tcx> PlaceTy<'tcx> {
/// `PlaceElem`, where we can just use the `Ty` that is already
/// stored inline on field projection elems.
pub fn projection_ty(self, tcx: TyCtxt<'tcx>, elem: PlaceElem<'tcx>) -> PlaceTy<'tcx> {
self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty)
self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty, |_, ty| ty)
}

/// `place_ty.projection_ty_core(tcx, elem, |...| { ... })`
@@ -71,6 +71,7 @@ impl<'tcx> PlaceTy<'tcx> {
param_env: ty::ParamEnv<'tcx>,
elem: &ProjectionElem<V, T>,
mut handle_field: impl FnMut(&Self, Field, T) -> Ty<'tcx>,
mut handle_opaque_cast: impl FnMut(&Self, T) -> Ty<'tcx>,
) -> PlaceTy<'tcx>
where
V: ::std::fmt::Debug,
@@ -109,6 +110,7 @@ impl<'tcx> PlaceTy<'tcx> {
PlaceTy { ty: self.ty, variant_index: Some(index) }
}
ProjectionElem::Field(f, fty) => PlaceTy::from_ty(handle_field(&self, f, fty)),
ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(handle_opaque_cast(&self, ty)),
};
debug!("projection_ty self: {:?} elem: {:?} yields: {:?}", self, elem, answer);
answer
7 changes: 6 additions & 1 deletion compiler/rustc_middle/src/mir/visit.rs
Original file line number Diff line number Diff line change
@@ -1094,6 +1094,11 @@ macro_rules! visit_place_fns {
self.visit_ty(&mut new_ty, TyContext::Location(location));
if ty != new_ty { Some(PlaceElem::Field(field, new_ty)) } else { None }
}
PlaceElem::OpaqueCast(ty) => {
let mut new_ty = ty;
self.visit_ty(&mut new_ty, TyContext::Location(location));
if ty != new_ty { Some(PlaceElem::OpaqueCast(new_ty)) } else { None }
}
PlaceElem::Deref
| PlaceElem::ConstantIndex { .. }
| PlaceElem::Subslice { .. }
@@ -1163,7 +1168,7 @@ macro_rules! visit_place_fns {
location: Location,
) {
match elem {
ProjectionElem::Field(_field, ty) => {
ProjectionElem::OpaqueCast(ty) | ProjectionElem::Field(_, ty) => {
self.visit_ty(ty, TyContext::Location(location));
}
ProjectionElem::Index(local) => {
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