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Move instantiate_opaque_types to rustc_infer. 

It does not depend on anything from rustc_trait_selection anymore.
This commit is contained in:
Oli Scherer 2021-10-28 14:12:24 +00:00
parent a8f06b249b
commit bc552fc417
6 changed files with 283 additions and 294 deletions
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1
compiler/rustc_borrowck/src/type_check/mod.rs
View File

@ -36,7 +36,6 @@ use rustc_span::def_id::CRATE_DEF_ID;
use rustc_span::{Span, DUMMY_SP};
use rustc_target::abi::VariantIdx;
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::opaque_types::InferCtxtExt;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_trait_selection::traits::query::type_op;
use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;

280
compiler/rustc_infer/src/infer/opaque_types.rs
View File

@ -1,8 +1,12 @@
use crate::infer::InferCtxt;
use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use crate::infer::{InferCtxt, InferOk};
use crate::traits;
use rustc_data_structures::sync::Lrc;
use rustc_data_structures::vec_map::VecMap;
use rustc_hir as hir;
use rustc_middle::ty::subst::GenericArgKind;
use rustc_hir::def_id::LocalDefId;
use rustc_middle::ty::fold::BottomUpFolder;
use rustc_middle::ty::subst::{GenericArgKind, Subst};
use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitor};
use rustc_span::Span;
@ -52,6 +56,49 @@ pub struct OpaqueTypeDecl<'tcx> {
}
impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
/// Replaces all opaque types in `value` with fresh inference variables
/// and creates appropriate obligations. For example, given the input:
///
/// impl Iterator<Item = impl Debug>
///
/// this method would create two type variables, `?0` and `?1`. It would
/// return the type `?0` but also the obligations:
///
/// ?0: Iterator<Item = ?1>
/// ?1: Debug
///
/// Moreover, it returns an `OpaqueTypeMap` that would map `?0` to
/// info about the `impl Iterator<..>` type and `?1` to info about
/// the `impl Debug` type.
///
/// # Parameters
///
/// - `parent_def_id` -- the `DefId` of the function in which the opaque type
/// is defined
/// - `body_id` -- the body-id with which the resulting obligations should
/// be associated
/// - `param_env` -- the in-scope parameter environment to be used for
/// obligations
/// - `value` -- the value within which we are instantiating opaque types
/// - `value_span` -- the span where the value came from, used in error reporting
pub fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
&self,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
value: T,
value_span: Span,
) -> InferOk<'tcx, T> {
debug!(
"instantiate_opaque_types(value={:?}, body_id={:?}, \
param_env={:?}, value_span={:?})",
value, body_id, param_env, value_span,
);
let mut instantiator =
Instantiator { infcx: self, body_id, param_env, value_span, obligations: vec![] };
let value = instantiator.instantiate_opaque_types_in_map(value);
InferOk { value, obligations: instantiator.obligations }
}
/// Given the map `opaque_types` containing the opaque
/// `impl Trait` types whose underlying, hidden types are being
/// inferred, this method adds constraints to the regions
@ -359,3 +406,232 @@ where
ControlFlow::CONTINUE
}
}
struct Instantiator<'a, 'tcx> {
infcx: &'a InferCtxt<'a, 'tcx>,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
value_span: Span,
obligations: Vec<traits::PredicateObligation<'tcx>>,
}
impl<'a, 'tcx> Instantiator<'a, 'tcx> {
fn instantiate_opaque_types_in_map<T: TypeFoldable<'tcx>>(&mut self, value: T) -> T {
let tcx = self.infcx.tcx;
value.fold_with(&mut BottomUpFolder {
tcx,
ty_op: |ty| {
if ty.references_error() {
return tcx.ty_error();
} else if let ty::Opaque(def_id, substs) = ty.kind() {
// Check that this is `impl Trait` type is
// declared by `parent_def_id` -- i.e., one whose
// value we are inferring. At present, this is
// always true during the first phase of
// type-check, but not always true later on during
// NLL. Once we support named opaque types more fully,
// this same scenario will be able to arise during all phases.
//
// Here is an example using type alias `impl Trait`
// that indicates the distinction we are checking for:
//
// ```rust
// mod a {
// pub type Foo = impl Iterator;
// pub fn make_foo() -> Foo { .. }
// }
//
// mod b {
// fn foo() -> a::Foo { a::make_foo() }
// }
// ```
//
// Here, the return type of `foo` references an
// `Opaque` indeed, but not one whose value is
// presently being inferred. You can get into a
// similar situation with closure return types
// today:
//
// ```rust
// fn foo() -> impl Iterator { .. }
// fn bar() {
// let x = || foo(); // returns the Opaque assoc with `foo`
// }
// ```
if let Some(def_id) = def_id.as_local() {
let opaque_hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
let parent_def_id = self.infcx.defining_use_anchor;
let def_scope_default = || {
let opaque_parent_hir_id = tcx.hir().get_parent_item(opaque_hir_id);
parent_def_id == tcx.hir().local_def_id(opaque_parent_hir_id)
};
let (in_definition_scope, origin) =
match tcx.hir().expect_item(opaque_hir_id).kind {
// Anonymous `impl Trait`
hir::ItemKind::OpaqueTy(hir::OpaqueTy {
impl_trait_fn: Some(parent),
origin,
..
}) => (parent == parent_def_id.to_def_id(), origin),
// Named `type Foo = impl Bar;`
hir::ItemKind::OpaqueTy(hir::OpaqueTy {
impl_trait_fn: None,
origin,
..
}) => (
may_define_opaque_type(tcx, parent_def_id, opaque_hir_id),
origin,
),
_ => (def_scope_default(), hir::OpaqueTyOrigin::TyAlias),
};
if in_definition_scope {
let opaque_type_key =
OpaqueTypeKey { def_id: def_id.to_def_id(), substs };
return self.fold_opaque_ty(ty, opaque_type_key, origin);
}
debug!(
"instantiate_opaque_types_in_map: \
encountered opaque outside its definition scope \
def_id={:?}",
def_id,
);
}
}
ty
},
lt_op: |lt| lt,
ct_op: |ct| ct,
})
}
#[instrument(skip(self), level = "debug")]
fn fold_opaque_ty(
&mut self,
ty: Ty<'tcx>,
opaque_type_key: OpaqueTypeKey<'tcx>,
origin: hir::OpaqueTyOrigin,
) -> Ty<'tcx> {
let infcx = self.infcx;
let tcx = infcx.tcx;
let OpaqueTypeKey { def_id, substs } = opaque_type_key;
// Use the same type variable if the exact same opaque type appears more
// than once in the return type (e.g., if it's passed to a type alias).
if let Some(opaque_defn) = infcx.inner.borrow().opaque_types.get(&opaque_type_key) {
debug!("re-using cached concrete type {:?}", opaque_defn.concrete_ty.kind());
return opaque_defn.concrete_ty;
}
let ty_var = infcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span: self.value_span,
});
// Ideally, we'd get the span where *this specific `ty` came
// from*, but right now we just use the span from the overall
// value being folded. In simple cases like `-> impl Foo`,
// these are the same span, but not in cases like `-> (impl
// Foo, impl Bar)`.
let definition_span = self.value_span;
{
let mut infcx = self.infcx.inner.borrow_mut();
infcx.opaque_types.insert(
OpaqueTypeKey { def_id, substs },
OpaqueTypeDecl { opaque_type: ty, definition_span, concrete_ty: ty_var, origin },
);
infcx.opaque_types_vars.insert(ty_var, ty);
}
debug!("generated new type inference var {:?}", ty_var.kind());
let item_bounds = tcx.explicit_item_bounds(def_id);
self.obligations.reserve(item_bounds.len());
for (predicate, _) in item_bounds {
debug!(?predicate);
let predicate = predicate.subst(tcx, substs);
debug!(?predicate);
// We can't normalize associated types from `rustc_infer`, but we can eagerly register inference variables for them.
let predicate = predicate.fold_with(&mut BottomUpFolder {
tcx,
ty_op: |ty| match ty.kind() {
ty::Projection(projection_ty) => infcx.infer_projection(
self.param_env,
*projection_ty,
traits::ObligationCause::misc(self.value_span, self.body_id),
0,
&mut self.obligations,
),
_ => ty,
},
lt_op: |lt| lt,
ct_op: |ct| ct,
});
debug!(?predicate);
if let ty::PredicateKind::Projection(projection) = predicate.kind().skip_binder() {
if projection.ty.references_error() {
// No point on adding these obligations since there's a type error involved.
return tcx.ty_error();
}
}
// Change the predicate to refer to the type variable,
// which will be the concrete type instead of the opaque type.
// This also instantiates nested instances of `impl Trait`.
let predicate = self.instantiate_opaque_types_in_map(predicate);
let cause =
traits::ObligationCause::new(self.value_span, self.body_id, traits::OpaqueType);
// Require that the predicate holds for the concrete type.
debug!(?predicate);
self.obligations.push(traits::Obligation::new(cause, self.param_env, predicate));
}
ty_var
}
}
/// Returns `true` if `opaque_hir_id` is a sibling or a child of a sibling of `def_id`.
///
/// Example:
/// ```rust
/// pub mod foo {
/// pub mod bar {
/// pub trait Bar { .. }
///
/// pub type Baz = impl Bar;
///
/// fn f1() -> Baz { .. }
/// }
///
/// fn f2() -> bar::Baz { .. }
/// }
/// ```
///
/// Here, `def_id` is the `LocalDefId` of the defining use of the opaque type (e.g., `f1` or `f2`),
/// and `opaque_hir_id` is the `HirId` of the definition of the opaque type `Baz`.
/// For the above example, this function returns `true` for `f1` and `false` for `f2`.
fn may_define_opaque_type(tcx: TyCtxt<'_>, def_id: LocalDefId, opaque_hir_id: hir::HirId) -> bool {
let mut hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
// Named opaque types can be defined by any siblings or children of siblings.
let scope = tcx.hir().get_defining_scope(opaque_hir_id);
// We walk up the node tree until we hit the root or the scope of the opaque type.
while hir_id != scope && hir_id != hir::CRATE_HIR_ID {
hir_id = tcx.hir().get_parent_item(hir_id);
}
// Syntactically, we are allowed to define the concrete type if:
let res = hir_id == scope;
trace!(
"may_define_opaque_type(def={:?}, opaque_node={:?}) = {}",
tcx.hir().find(hir_id),
tcx.hir().get(opaque_hir_id),
res
);
res
}

293
compiler/rustc_trait_selection/src/opaque_types.rs
View File

@ -1,25 +1,14 @@
use crate::traits::{self, ObligationCause, PredicateObligation};
use crate::traits;
use rustc_data_structures::fx::FxHashMap;
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::def_id::DefId;
use rustc_infer::infer::error_reporting::unexpected_hidden_region_diagnostic;
use rustc_infer::infer::opaque_types::OpaqueTypeDecl;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::{InferCtxt, InferOk};
use rustc_middle::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst};
use rustc_infer::infer::InferCtxt;
use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts};
use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt};
use rustc_span::Span;
pub trait InferCtxtExt<'tcx> {
fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
&self,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
value: T,
value_span: Span,
) -> InferOk<'tcx, T>;
fn infer_opaque_definition_from_instantiation(
&self,
opaque_type_key: OpaqueTypeKey<'tcx>,
@ -29,49 +18,6 @@ pub trait InferCtxtExt<'tcx> {
}
impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
/// Replaces all opaque types in `value` with fresh inference variables
/// and creates appropriate obligations. For example, given the input:
///
/// impl Iterator<Item = impl Debug>
///
/// this method would create two type variables, `?0` and `?1`. It would
/// return the type `?0` but also the obligations:
///
/// ?0: Iterator<Item = ?1>
/// ?1: Debug
///
/// Moreover, it returns an `OpaqueTypeMap` that would map `?0` to
/// info about the `impl Iterator<..>` type and `?1` to info about
/// the `impl Debug` type.
///
/// # Parameters
///
/// - `parent_def_id` -- the `DefId` of the function in which the opaque type
/// is defined
/// - `body_id` -- the body-id with which the resulting obligations should
/// be associated
/// - `param_env` -- the in-scope parameter environment to be used for
/// obligations
/// - `value` -- the value within which we are instantiating opaque types
/// - `value_span` -- the span where the value came from, used in error reporting
fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
&self,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
value: T,
value_span: Span,
) -> InferOk<'tcx, T> {
debug!(
"instantiate_opaque_types(value={:?}, body_id={:?}, \
param_env={:?}, value_span={:?})",
value, body_id, param_env, value_span,
);
let mut instantiator =
Instantiator { infcx: self, body_id, param_env, value_span, obligations: vec![] };
let value = instantiator.instantiate_opaque_types_in_map(value);
InferOk { value, obligations: instantiator.obligations }
}
/// Given the fully resolved, instantiated type for an opaque
/// type, i.e., the value of an inference variable like C1 or C2
/// (*), computes the "definition type" for an opaque type
@ -375,235 +321,6 @@ impl TypeFolder<'tcx> for ReverseMapper<'tcx> {
}
}
struct Instantiator<'a, 'tcx> {
infcx: &'a InferCtxt<'a, 'tcx>,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
value_span: Span,
obligations: Vec<PredicateObligation<'tcx>>,
}
impl<'a, 'tcx> Instantiator<'a, 'tcx> {
fn instantiate_opaque_types_in_map<T: TypeFoldable<'tcx>>(&mut self, value: T) -> T {
let tcx = self.infcx.tcx;
value.fold_with(&mut BottomUpFolder {
tcx,
ty_op: |ty| {
if ty.references_error() {
return tcx.ty_error();
} else if let ty::Opaque(def_id, substs) = ty.kind() {
// Check that this is `impl Trait` type is
// declared by `parent_def_id` -- i.e., one whose
// value we are inferring. At present, this is
// always true during the first phase of
// type-check, but not always true later on during
// NLL. Once we support named opaque types more fully,
// this same scenario will be able to arise during all phases.
//
// Here is an example using type alias `impl Trait`
// that indicates the distinction we are checking for:
//
// ```rust
// mod a {
// pub type Foo = impl Iterator;
// pub fn make_foo() -> Foo { .. }
// }
//
// mod b {
// fn foo() -> a::Foo { a::make_foo() }
// }
// ```
//
// Here, the return type of `foo` references an
// `Opaque` indeed, but not one whose value is
// presently being inferred. You can get into a
// similar situation with closure return types
// today:
//
// ```rust
// fn foo() -> impl Iterator { .. }
// fn bar() {
// let x = || foo(); // returns the Opaque assoc with `foo`
// }
// ```
if let Some(def_id) = def_id.as_local() {
let opaque_hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
let parent_def_id = self.infcx.defining_use_anchor;
let def_scope_default = || {
let opaque_parent_hir_id = tcx.hir().get_parent_item(opaque_hir_id);
parent_def_id == tcx.hir().local_def_id(opaque_parent_hir_id)
};
let (in_definition_scope, origin) =
match tcx.hir().expect_item(opaque_hir_id).kind {
// Anonymous `impl Trait`
hir::ItemKind::OpaqueTy(hir::OpaqueTy {
impl_trait_fn: Some(parent),
origin,
..
}) => (parent == parent_def_id.to_def_id(), origin),
// Named `type Foo = impl Bar;`
hir::ItemKind::OpaqueTy(hir::OpaqueTy {
impl_trait_fn: None,
origin,
..
}) => (
may_define_opaque_type(tcx, parent_def_id, opaque_hir_id),
origin,
),
_ => (def_scope_default(), hir::OpaqueTyOrigin::TyAlias),
};
if in_definition_scope {
let opaque_type_key =
OpaqueTypeKey { def_id: def_id.to_def_id(), substs };
return self.fold_opaque_ty(ty, opaque_type_key, origin);
}
debug!(
"instantiate_opaque_types_in_map: \
encountered opaque outside its definition scope \
def_id={:?}",
def_id,
);
}
}
ty
},
lt_op: |lt| lt,
ct_op: |ct| ct,
})
}
#[instrument(skip(self), level = "debug")]
fn fold_opaque_ty(
&mut self,
ty: Ty<'tcx>,
opaque_type_key: OpaqueTypeKey<'tcx>,
origin: hir::OpaqueTyOrigin,
) -> Ty<'tcx> {
let infcx = self.infcx;
let tcx = infcx.tcx;
let OpaqueTypeKey { def_id, substs } = opaque_type_key;
// Use the same type variable if the exact same opaque type appears more
// than once in the return type (e.g., if it's passed to a type alias).
if let Some(opaque_defn) = infcx.inner.borrow().opaque_types.get(&opaque_type_key) {
debug!("re-using cached concrete type {:?}", opaque_defn.concrete_ty.kind());
return opaque_defn.concrete_ty;
}
let ty_var = infcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span: self.value_span,
});
// Ideally, we'd get the span where *this specific `ty` came
// from*, but right now we just use the span from the overall
// value being folded. In simple cases like `-> impl Foo`,
// these are the same span, but not in cases like `-> (impl
// Foo, impl Bar)`.
let definition_span = self.value_span;
{
let mut infcx = self.infcx.inner.borrow_mut();
infcx.opaque_types.insert(
OpaqueTypeKey { def_id, substs },
OpaqueTypeDecl { opaque_type: ty, definition_span, concrete_ty: ty_var, origin },
);
infcx.opaque_types_vars.insert(ty_var, ty);
}
debug!("generated new type inference var {:?}", ty_var.kind());
let item_bounds = tcx.explicit_item_bounds(def_id);
self.obligations.reserve(item_bounds.len());
for (predicate, _) in item_bounds {
debug!(?predicate);
let predicate = predicate.subst(tcx, substs);
debug!(?predicate);
// We can't normalize associated types from `rustc_infer`, but we can eagerly register inference variables for them.
let predicate = predicate.fold_with(&mut BottomUpFolder {
tcx,
ty_op: |ty| match ty.kind() {
ty::Projection(projection_ty) => infcx.infer_projection(
self.param_env,
*projection_ty,
ObligationCause::misc(self.value_span, self.body_id),
0,
&mut self.obligations,
),
_ => ty,
},
lt_op: |lt| lt,
ct_op: |ct| ct,
});
debug!(?predicate);
if let ty::PredicateKind::Projection(projection) = predicate.kind().skip_binder() {
if projection.ty.references_error() {
// No point on adding these obligations since there's a type error involved.
return tcx.ty_error();
}
}
// Change the predicate to refer to the type variable,
// which will be the concrete type instead of the opaque type.
// This also instantiates nested instances of `impl Trait`.
let predicate = self.instantiate_opaque_types_in_map(predicate);
let cause =
traits::ObligationCause::new(self.value_span, self.body_id, traits::OpaqueType);
// Require that the predicate holds for the concrete type.
debug!(?predicate);
self.obligations.push(traits::Obligation::new(cause, self.param_env, predicate));
}
ty_var
}
}
/// Returns `true` if `opaque_hir_id` is a sibling or a child of a sibling of `def_id`.
///
/// Example:
/// ```rust
/// pub mod foo {
/// pub mod bar {
/// pub trait Bar { .. }
///
/// pub type Baz = impl Bar;
///
/// fn f1() -> Baz { .. }
/// }
///
/// fn f2() -> bar::Baz { .. }
/// }
/// ```
///
/// Here, `def_id` is the `LocalDefId` of the defining use of the opaque type (e.g., `f1` or `f2`),
/// and `opaque_hir_id` is the `HirId` of the definition of the opaque type `Baz`.
/// For the above example, this function returns `true` for `f1` and `false` for `f2`.
fn may_define_opaque_type(tcx: TyCtxt<'_>, def_id: LocalDefId, opaque_hir_id: hir::HirId) -> bool {
let mut hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
// Named opaque types can be defined by any siblings or children of siblings.
let scope = tcx.hir().get_defining_scope(opaque_hir_id);
// We walk up the node tree until we hit the root or the scope of the opaque type.
while hir_id != scope && hir_id != hir::CRATE_HIR_ID {
hir_id = tcx.hir().get_parent_item(hir_id);
}
// Syntactically, we are allowed to define the concrete type if:
let res = hir_id == scope;
trace!(
"may_define_opaque_type(def={:?}, opaque_node={:?}) = {}",
tcx.hir().find(hir_id),
tcx.hir().get(opaque_hir_id),
res
);
res
}
/// Given a set of predicates that apply to an object type, returns
/// the region bounds that the (erased) `Self` type must
/// outlive. Precisely *because* the `Self` type is erased, the

1
compiler/rustc_typeck/src/check/_match.rs
View File

@ -6,7 +6,6 @@ use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKi
use rustc_infer::traits::Obligation;
use rustc_middle::ty::{self, ToPredicate, Ty, TyS};
use rustc_span::{MultiSpan, Span};
use rustc_trait_selection::opaque_types::InferCtxtExt as _;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use rustc_trait_selection::traits::{
IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,

1
compiler/rustc_typeck/src/check/check.rs
View File

@ -21,7 +21,6 @@ use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVE
use rustc_span::symbol::sym;
use rustc_span::{self, MultiSpan, Span};
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::opaque_types::InferCtxtExt as _;
use rustc_trait_selection::traits;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_ty_utils::representability::{self, Representability};

1
compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
View File

@ -35,7 +35,6 @@ use rustc_span::source_map::{original_sp, DUMMY_SP};
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::{self, BytePos, MultiSpan, Span};
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::opaque_types::InferCtxtExt as _;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_trait_selection::traits::{
self, ObligationCause, ObligationCauseCode, StatementAsExpression, TraitEngine, TraitEngineExt,