Auto merge of #90387 - matthiaskrgr:rollup-b2x8v0x, r=matthiaskrgr
Rollup of 3 pull requests Successful merges: - #90082 (Fix minor typos) - #90336 (Remove extra lines in examples for `Duration::try_from_secs_*`) - #90376 (Various cleanups around opaque types) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
This commit is contained in:
bors
commit
df76418f1e
9 changed files with 599 additions and 655 deletions
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@ -36,7 +36,6 @@ use rustc_span::def_id::CRATE_DEF_ID;
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use rustc_span::{Span, DUMMY_SP};
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use rustc_target::abi::VariantIdx;
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use rustc_trait_selection::infer::InferCtxtExt as _;
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use rustc_trait_selection::opaque_types::InferCtxtExt;
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use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
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use rustc_trait_selection::traits::query::type_op;
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use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
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@ -1,8 +1,17 @@
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use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
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use crate::infer::{InferCtxt, InferOk};
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use crate::traits;
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use rustc_data_structures::sync::Lrc;
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use rustc_data_structures::vec_map::VecMap;
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use rustc_hir as hir;
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use rustc_middle::ty::{OpaqueTypeKey, Ty};
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use rustc_hir::def_id::LocalDefId;
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use rustc_middle::ty::fold::BottomUpFolder;
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use rustc_middle::ty::subst::{GenericArgKind, Subst};
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use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitor};
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use rustc_span::Span;
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use std::ops::ControlFlow;
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pub type OpaqueTypeMap<'tcx> = VecMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>;
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/// Information about the opaque types whose values we
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@ -45,3 +54,584 @@ pub struct OpaqueTypeDecl<'tcx> {
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/// The origin of the opaque type.
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pub origin: hir::OpaqueTyOrigin,
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}
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impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
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/// Replaces all opaque types in `value` with fresh inference variables
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/// and creates appropriate obligations. For example, given the input:
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///
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/// impl Iterator<Item = impl Debug>
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///
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/// this method would create two type variables, `?0` and `?1`. It would
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/// return the type `?0` but also the obligations:
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///
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/// ?0: Iterator<Item = ?1>
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/// ?1: Debug
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///
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/// Moreover, it returns an `OpaqueTypeMap` that would map `?0` to
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/// info about the `impl Iterator<..>` type and `?1` to info about
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/// the `impl Debug` type.
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///
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/// # Parameters
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///
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/// - `parent_def_id` -- the `DefId` of the function in which the opaque type
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/// is defined
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/// - `body_id` -- the body-id with which the resulting obligations should
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/// be associated
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/// - `param_env` -- the in-scope parameter environment to be used for
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/// obligations
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/// - `value` -- the value within which we are instantiating opaque types
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/// - `value_span` -- the span where the value came from, used in error reporting
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pub fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
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&self,
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body_id: hir::HirId,
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param_env: ty::ParamEnv<'tcx>,
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value: T,
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value_span: Span,
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) -> InferOk<'tcx, T> {
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debug!(
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"instantiate_opaque_types(value={:?}, body_id={:?}, \
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param_env={:?}, value_span={:?})",
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value, body_id, param_env, value_span,
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);
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let mut instantiator =
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Instantiator { infcx: self, body_id, param_env, value_span, obligations: vec![] };
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let value = instantiator.instantiate_opaque_types_in_map(value);
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InferOk { value, obligations: instantiator.obligations }
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}
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/// Given the map `opaque_types` containing the opaque
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/// `impl Trait` types whose underlying, hidden types are being
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/// inferred, this method adds constraints to the regions
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/// appearing in those underlying hidden types to ensure that they
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/// at least do not refer to random scopes within the current
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/// function. These constraints are not (quite) sufficient to
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/// guarantee that the regions are actually legal values; that
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/// final condition is imposed after region inference is done.
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///
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/// # The Problem
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///
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/// Let's work through an example to explain how it works. Assume
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/// the current function is as follows:
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///
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/// ```text
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/// fn foo<'a, 'b>(..) -> (impl Bar<'a>, impl Bar<'b>)
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/// ```
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///
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/// Here, we have two `impl Trait` types whose values are being
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/// inferred (the `impl Bar<'a>` and the `impl
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/// Bar<'b>`). Conceptually, this is sugar for a setup where we
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/// define underlying opaque types (`Foo1`, `Foo2`) and then, in
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/// the return type of `foo`, we *reference* those definitions:
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///
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/// ```text
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/// type Foo1<'x> = impl Bar<'x>;
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/// type Foo2<'x> = impl Bar<'x>;
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/// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
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/// // ^^^^ ^^
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/// // | |
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/// // | substs
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/// // def_id
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/// ```
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///
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/// As indicating in the comments above, each of those references
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/// is (in the compiler) basically a substitution (`substs`)
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/// applied to the type of a suitable `def_id` (which identifies
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/// `Foo1` or `Foo2`).
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///
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/// Now, at this point in compilation, what we have done is to
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/// replace each of the references (`Foo1<'a>`, `Foo2<'b>`) with
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/// fresh inference variables C1 and C2. We wish to use the values
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/// of these variables to infer the underlying types of `Foo1` and
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/// `Foo2`. That is, this gives rise to higher-order (pattern) unification
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/// constraints like:
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///
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/// ```text
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/// for<'a> (Foo1<'a> = C1)
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/// for<'b> (Foo1<'b> = C2)
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/// ```
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///
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/// For these equation to be satisfiable, the types `C1` and `C2`
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/// can only refer to a limited set of regions. For example, `C1`
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/// can only refer to `'static` and `'a`, and `C2` can only refer
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/// to `'static` and `'b`. The job of this function is to impose that
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/// constraint.
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///
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/// Up to this point, C1 and C2 are basically just random type
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/// inference variables, and hence they may contain arbitrary
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/// regions. In fact, it is fairly likely that they do! Consider
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/// this possible definition of `foo`:
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///
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/// ```text
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/// fn foo<'a, 'b>(x: &'a i32, y: &'b i32) -> (impl Bar<'a>, impl Bar<'b>) {
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/// (&*x, &*y)
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/// }
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/// ```
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///
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/// Here, the values for the concrete types of the two impl
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/// traits will include inference variables:
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///
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/// ```text
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/// &'0 i32
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/// &'1 i32
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/// ```
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///
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/// Ordinarily, the subtyping rules would ensure that these are
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/// sufficiently large. But since `impl Bar<'a>` isn't a specific
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/// type per se, we don't get such constraints by default. This
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/// is where this function comes into play. It adds extra
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/// constraints to ensure that all the regions which appear in the
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/// inferred type are regions that could validly appear.
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///
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/// This is actually a bit of a tricky constraint in general. We
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/// want to say that each variable (e.g., `'0`) can only take on
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/// values that were supplied as arguments to the opaque type
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/// (e.g., `'a` for `Foo1<'a>`) or `'static`, which is always in
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/// scope. We don't have a constraint quite of this kind in the current
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/// region checker.
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///
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/// # The Solution
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///
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/// We generally prefer to make `<=` constraints, since they
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/// integrate best into the region solver. To do that, we find the
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/// "minimum" of all the arguments that appear in the substs: that
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/// is, some region which is less than all the others. In the case
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/// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
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/// all). Then we apply that as a least bound to the variables
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/// (e.g., `'a <= '0`).
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///
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/// In some cases, there is no minimum. Consider this example:
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///
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/// ```text
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/// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... }
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/// ```
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///
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/// Here we would report a more complex "in constraint", like `'r
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/// in ['a, 'b, 'static]` (where `'r` is some region appearing in
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/// the hidden type).
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///
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/// # Constrain regions, not the hidden concrete type
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///
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/// Note that generating constraints on each region `Rc` is *not*
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/// the same as generating an outlives constraint on `Tc` iself.
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/// For example, if we had a function like this:
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///
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/// ```rust
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/// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> {
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/// (x, y)
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/// }
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///
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/// // Equivalent to:
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/// type FooReturn<'a, T> = impl Foo<'a>;
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/// fn foo<'a, T>(..) -> FooReturn<'a, T> { .. }
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/// ```
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///
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/// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0`
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/// is an inference variable). If we generated a constraint that
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/// `Tc: 'a`, then this would incorrectly require that `T: 'a` --
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/// but this is not necessary, because the opaque type we
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/// create will be allowed to reference `T`. So we only generate a
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/// constraint that `'0: 'a`.
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///
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/// # The `free_region_relations` parameter
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///
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/// The `free_region_relations` argument is used to find the
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/// "minimum" of the regions supplied to a given opaque type.
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/// It must be a relation that can answer whether `'a <= 'b`,
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/// where `'a` and `'b` are regions that appear in the "substs"
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/// for the opaque type references (the `<'a>` in `Foo1<'a>`).
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///
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/// Note that we do not impose the constraints based on the
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/// generic regions from the `Foo1` definition (e.g., `'x`). This
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/// is because the constraints we are imposing here is basically
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/// the concern of the one generating the constraining type C1,
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/// which is the current function. It also means that we can
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/// take "implied bounds" into account in some cases:
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///
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/// ```text
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/// trait SomeTrait<'a, 'b> { }
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/// fn foo<'a, 'b>(_: &'a &'b u32) -> impl SomeTrait<'a, 'b> { .. }
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/// ```
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///
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/// Here, the fact that `'b: 'a` is known only because of the
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/// implied bounds from the `&'a &'b u32` parameter, and is not
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/// "inherent" to the opaque type definition.
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///
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/// # Parameters
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///
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/// - `opaque_types` -- the map produced by `instantiate_opaque_types`
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/// - `free_region_relations` -- something that can be used to relate
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/// the free regions (`'a`) that appear in the impl trait.
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#[instrument(level = "debug", skip(self))]
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pub fn constrain_opaque_type(
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&self,
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opaque_type_key: OpaqueTypeKey<'tcx>,
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opaque_defn: &OpaqueTypeDecl<'tcx>,
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) {
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let def_id = opaque_type_key.def_id;
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let tcx = self.tcx;
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let concrete_ty = self.resolve_vars_if_possible(opaque_defn.concrete_ty);
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debug!(?concrete_ty);
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let first_own_region = match opaque_defn.origin {
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hir::OpaqueTyOrigin::FnReturn | hir::OpaqueTyOrigin::AsyncFn => {
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// We lower
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//
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// fn foo<'l0..'ln>() -> impl Trait<'l0..'lm>
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//
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// into
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//
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// type foo::<'p0..'pn>::Foo<'q0..'qm>
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// fn foo<l0..'ln>() -> foo::<'static..'static>::Foo<'l0..'lm>.
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//
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// For these types we only iterate over `'l0..lm` below.
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tcx.generics_of(def_id).parent_count
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}
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// These opaque type inherit all lifetime parameters from their
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// parent, so we have to check them all.
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hir::OpaqueTyOrigin::TyAlias => 0,
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};
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// For a case like `impl Foo<'a, 'b>`, we would generate a constraint
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// `'r in ['a, 'b, 'static]` for each region `'r` that appears in the
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// hidden type (i.e., it must be equal to `'a`, `'b`, or `'static`).
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//
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// `conflict1` and `conflict2` are the two region bounds that we
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// detected which were unrelated. They are used for diagnostics.
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// Create the set of choice regions: each region in the hidden
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// type can be equal to any of the region parameters of the
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// opaque type definition.
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let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new(
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opaque_type_key.substs[first_own_region..]
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.iter()
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.filter_map(|arg| match arg.unpack() {
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GenericArgKind::Lifetime(r) => Some(r),
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GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
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||||
})
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.chain(std::iter::once(self.tcx.lifetimes.re_static))
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.collect(),
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);
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concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
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tcx: self.tcx,
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op: |r| {
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self.member_constraint(
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opaque_type_key.def_id,
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opaque_defn.definition_span,
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concrete_ty,
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r,
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&choice_regions,
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)
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},
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});
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}
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}
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// Visitor that requires that (almost) all regions in the type visited outlive
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// `least_region`. We cannot use `push_outlives_components` because regions in
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// closure signatures are not included in their outlives components. We need to
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// ensure all regions outlive the given bound so that we don't end up with,
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// say, `ReVar` appearing in a return type and causing ICEs when other
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// functions end up with region constraints involving regions from other
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// functions.
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//
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// We also cannot use `for_each_free_region` because for closures it includes
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// the regions parameters from the enclosing item.
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//
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// We ignore any type parameters because impl trait values are assumed to
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// capture all the in-scope type parameters.
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struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP> {
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tcx: TyCtxt<'tcx>,
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op: OP,
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}
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impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
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where
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OP: FnMut(ty::Region<'tcx>),
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{
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fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
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Some(self.tcx)
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}
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fn visit_binder<T: TypeFoldable<'tcx>>(
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&mut self,
|
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t: &ty::Binder<'tcx, T>,
|
||||
) -> ControlFlow<Self::BreakTy> {
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t.as_ref().skip_binder().visit_with(self);
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ControlFlow::CONTINUE
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||||
}
|
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|
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fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
|
||||
match *r {
|
||||
// ignore bound regions, keep visiting
|
||||
ty::ReLateBound(_, _) => ControlFlow::CONTINUE,
|
||||
_ => {
|
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(self.op)(r);
|
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ControlFlow::CONTINUE
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
|
||||
// We're only interested in types involving regions
|
||||
if !ty.flags().intersects(ty::TypeFlags::HAS_POTENTIAL_FREE_REGIONS) {
|
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return ControlFlow::CONTINUE;
|
||||
}
|
||||
|
||||
match ty.kind() {
|
||||
ty::Closure(_, ref substs) => {
|
||||
// Skip lifetime parameters of the enclosing item(s)
|
||||
|
||||
substs.as_closure().tupled_upvars_ty().visit_with(self);
|
||||
substs.as_closure().sig_as_fn_ptr_ty().visit_with(self);
|
||||
}
|
||||
|
||||
ty::Generator(_, ref substs, _) => {
|
||||
// Skip lifetime parameters of the enclosing item(s)
|
||||
// Also skip the witness type, because that has no free regions.
|
||||
|
||||
substs.as_generator().tupled_upvars_ty().visit_with(self);
|
||||
substs.as_generator().return_ty().visit_with(self);
|
||||
substs.as_generator().yield_ty().visit_with(self);
|
||||
substs.as_generator().resume_ty().visit_with(self);
|
||||
}
|
||||
_ => {
|
||||
ty.super_visit_with(self);
|
||||
}
|
||||
}
|
||||
|
||||
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
|
||||
}
|
||||
|
|
|
|||
|
|
@ -1,45 +1,14 @@
|
|||
use crate::traits::{self, ObligationCause, PredicateObligation};
|
||||
use crate::traits;
|
||||
use rustc_data_structures::fx::FxHashMap;
|
||||
use rustc_data_structures::sync::Lrc;
|
||||
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, TypeVisitor};
|
||||
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;
|
||||
|
||||
use std::ops::ControlFlow;
|
||||
|
||||
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 constrain_opaque_types(&self);
|
||||
|
||||
fn constrain_opaque_type(
|
||||
&self,
|
||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
||||
opaque_defn: &OpaqueTypeDecl<'tcx>,
|
||||
);
|
||||
|
||||
/*private*/
|
||||
fn generate_member_constraint(
|
||||
&self,
|
||||
concrete_ty: Ty<'tcx>,
|
||||
opaque_defn: &OpaqueTypeDecl<'tcx>,
|
||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
||||
first_own_region_index: usize,
|
||||
);
|
||||
|
||||
fn infer_opaque_definition_from_instantiation(
|
||||
&self,
|
||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
||||
|
|
@ -49,305 +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 map `opaque_types` containing the opaque
|
||||
/// `impl Trait` types whose underlying, hidden types are being
|
||||
/// inferred, this method adds constraints to the regions
|
||||
/// appearing in those underlying hidden types to ensure that they
|
||||
/// at least do not refer to random scopes within the current
|
||||
/// function. These constraints are not (quite) sufficient to
|
||||
/// guarantee that the regions are actually legal values; that
|
||||
/// final condition is imposed after region inference is done.
|
||||
///
|
||||
/// # The Problem
|
||||
///
|
||||
/// Let's work through an example to explain how it works. Assume
|
||||
/// the current function is as follows:
|
||||
///
|
||||
/// ```text
|
||||
/// fn foo<'a, 'b>(..) -> (impl Bar<'a>, impl Bar<'b>)
|
||||
/// ```
|
||||
///
|
||||
/// Here, we have two `impl Trait` types whose values are being
|
||||
/// inferred (the `impl Bar<'a>` and the `impl
|
||||
/// Bar<'b>`). Conceptually, this is sugar for a setup where we
|
||||
/// define underlying opaque types (`Foo1`, `Foo2`) and then, in
|
||||
/// the return type of `foo`, we *reference* those definitions:
|
||||
///
|
||||
/// ```text
|
||||
/// type Foo1<'x> = impl Bar<'x>;
|
||||
/// type Foo2<'x> = impl Bar<'x>;
|
||||
/// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
|
||||
/// // ^^^^ ^^
|
||||
/// // | |
|
||||
/// // | substs
|
||||
/// // def_id
|
||||
/// ```
|
||||
///
|
||||
/// As indicating in the comments above, each of those references
|
||||
/// is (in the compiler) basically a substitution (`substs`)
|
||||
/// applied to the type of a suitable `def_id` (which identifies
|
||||
/// `Foo1` or `Foo2`).
|
||||
///
|
||||
/// Now, at this point in compilation, what we have done is to
|
||||
/// replace each of the references (`Foo1<'a>`, `Foo2<'b>`) with
|
||||
/// fresh inference variables C1 and C2. We wish to use the values
|
||||
/// of these variables to infer the underlying types of `Foo1` and
|
||||
/// `Foo2`. That is, this gives rise to higher-order (pattern) unification
|
||||
/// constraints like:
|
||||
///
|
||||
/// ```text
|
||||
/// for<'a> (Foo1<'a> = C1)
|
||||
/// for<'b> (Foo1<'b> = C2)
|
||||
/// ```
|
||||
///
|
||||
/// For these equation to be satisfiable, the types `C1` and `C2`
|
||||
/// can only refer to a limited set of regions. For example, `C1`
|
||||
/// can only refer to `'static` and `'a`, and `C2` can only refer
|
||||
/// to `'static` and `'b`. The job of this function is to impose that
|
||||
/// constraint.
|
||||
///
|
||||
/// Up to this point, C1 and C2 are basically just random type
|
||||
/// inference variables, and hence they may contain arbitrary
|
||||
/// regions. In fact, it is fairly likely that they do! Consider
|
||||
/// this possible definition of `foo`:
|
||||
///
|
||||
/// ```text
|
||||
/// fn foo<'a, 'b>(x: &'a i32, y: &'b i32) -> (impl Bar<'a>, impl Bar<'b>) {
|
||||
/// (&*x, &*y)
|
||||
/// }
|
||||
/// ```
|
||||
///
|
||||
/// Here, the values for the concrete types of the two impl
|
||||
/// traits will include inference variables:
|
||||
///
|
||||
/// ```text
|
||||
/// &'0 i32
|
||||
/// &'1 i32
|
||||
/// ```
|
||||
///
|
||||
/// Ordinarily, the subtyping rules would ensure that these are
|
||||
/// sufficiently large. But since `impl Bar<'a>` isn't a specific
|
||||
/// type per se, we don't get such constraints by default. This
|
||||
/// is where this function comes into play. It adds extra
|
||||
/// constraints to ensure that all the regions which appear in the
|
||||
/// inferred type are regions that could validly appear.
|
||||
///
|
||||
/// This is actually a bit of a tricky constraint in general. We
|
||||
/// want to say that each variable (e.g., `'0`) can only take on
|
||||
/// values that were supplied as arguments to the opaque type
|
||||
/// (e.g., `'a` for `Foo1<'a>`) or `'static`, which is always in
|
||||
/// scope. We don't have a constraint quite of this kind in the current
|
||||
/// region checker.
|
||||
///
|
||||
/// # The Solution
|
||||
///
|
||||
/// We generally prefer to make `<=` constraints, since they
|
||||
/// integrate best into the region solver. To do that, we find the
|
||||
/// "minimum" of all the arguments that appear in the substs: that
|
||||
/// is, some region which is less than all the others. In the case
|
||||
/// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
|
||||
/// all). Then we apply that as a least bound to the variables
|
||||
/// (e.g., `'a <= '0`).
|
||||
///
|
||||
/// In some cases, there is no minimum. Consider this example:
|
||||
///
|
||||
/// ```text
|
||||
/// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... }
|
||||
/// ```
|
||||
///
|
||||
/// Here we would report a more complex "in constraint", like `'r
|
||||
/// in ['a, 'b, 'static]` (where `'r` is some region appearing in
|
||||
/// the hidden type).
|
||||
///
|
||||
/// # Constrain regions, not the hidden concrete type
|
||||
///
|
||||
/// Note that generating constraints on each region `Rc` is *not*
|
||||
/// the same as generating an outlives constraint on `Tc` iself.
|
||||
/// For example, if we had a function like this:
|
||||
///
|
||||
/// ```rust
|
||||
/// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> {
|
||||
/// (x, y)
|
||||
/// }
|
||||
///
|
||||
/// // Equivalent to:
|
||||
/// type FooReturn<'a, T> = impl Foo<'a>;
|
||||
/// fn foo<'a, T>(..) -> FooReturn<'a, T> { .. }
|
||||
/// ```
|
||||
///
|
||||
/// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0`
|
||||
/// is an inference variable). If we generated a constraint that
|
||||
/// `Tc: 'a`, then this would incorrectly require that `T: 'a` --
|
||||
/// but this is not necessary, because the opaque type we
|
||||
/// create will be allowed to reference `T`. So we only generate a
|
||||
/// constraint that `'0: 'a`.
|
||||
///
|
||||
/// # The `free_region_relations` parameter
|
||||
///
|
||||
/// The `free_region_relations` argument is used to find the
|
||||
/// "minimum" of the regions supplied to a given opaque type.
|
||||
/// It must be a relation that can answer whether `'a <= 'b`,
|
||||
/// where `'a` and `'b` are regions that appear in the "substs"
|
||||
/// for the opaque type references (the `<'a>` in `Foo1<'a>`).
|
||||
///
|
||||
/// Note that we do not impose the constraints based on the
|
||||
/// generic regions from the `Foo1` definition (e.g., `'x`). This
|
||||
/// is because the constraints we are imposing here is basically
|
||||
/// the concern of the one generating the constraining type C1,
|
||||
/// which is the current function. It also means that we can
|
||||
/// take "implied bounds" into account in some cases:
|
||||
///
|
||||
/// ```text
|
||||
/// trait SomeTrait<'a, 'b> { }
|
||||
/// fn foo<'a, 'b>(_: &'a &'b u32) -> impl SomeTrait<'a, 'b> { .. }
|
||||
/// ```
|
||||
///
|
||||
/// Here, the fact that `'b: 'a` is known only because of the
|
||||
/// implied bounds from the `&'a &'b u32` parameter, and is not
|
||||
/// "inherent" to the opaque type definition.
|
||||
///
|
||||
/// # Parameters
|
||||
///
|
||||
/// - `opaque_types` -- the map produced by `instantiate_opaque_types`
|
||||
/// - `free_region_relations` -- something that can be used to relate
|
||||
/// the free regions (`'a`) that appear in the impl trait.
|
||||
fn constrain_opaque_types(&self) {
|
||||
let opaque_types = self.inner.borrow().opaque_types.clone();
|
||||
for (opaque_type_key, opaque_defn) in opaque_types {
|
||||
self.constrain_opaque_type(opaque_type_key, &opaque_defn);
|
||||
}
|
||||
}
|
||||
|
||||
/// See `constrain_opaque_types` for documentation.
|
||||
#[instrument(level = "debug", skip(self))]
|
||||
fn constrain_opaque_type(
|
||||
&self,
|
||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
||||
opaque_defn: &OpaqueTypeDecl<'tcx>,
|
||||
) {
|
||||
let def_id = opaque_type_key.def_id;
|
||||
|
||||
let tcx = self.tcx;
|
||||
|
||||
let concrete_ty = self.resolve_vars_if_possible(opaque_defn.concrete_ty);
|
||||
|
||||
debug!(?concrete_ty);
|
||||
|
||||
let first_own_region = match opaque_defn.origin {
|
||||
hir::OpaqueTyOrigin::FnReturn | hir::OpaqueTyOrigin::AsyncFn => {
|
||||
// We lower
|
||||
//
|
||||
// fn foo<'l0..'ln>() -> impl Trait<'l0..'lm>
|
||||
//
|
||||
// into
|
||||
//
|
||||
// type foo::<'p0..'pn>::Foo<'q0..'qm>
|
||||
// fn foo<l0..'ln>() -> foo::<'static..'static>::Foo<'l0..'lm>.
|
||||
//
|
||||
// For these types we only iterate over `'l0..lm` below.
|
||||
tcx.generics_of(def_id).parent_count
|
||||
}
|
||||
// These opaque type inherit all lifetime parameters from their
|
||||
// parent, so we have to check them all.
|
||||
hir::OpaqueTyOrigin::TyAlias => 0,
|
||||
};
|
||||
|
||||
// The regions that appear in the hidden type must be equal to
|
||||
// one of the regions in scope for the opaque type.
|
||||
self.generate_member_constraint(
|
||||
concrete_ty,
|
||||
opaque_defn,
|
||||
opaque_type_key,
|
||||
first_own_region,
|
||||
);
|
||||
}
|
||||
|
||||
/// As a fallback, we sometimes generate an "in constraint". For
|
||||
/// a case like `impl Foo<'a, 'b>`, where `'a` and `'b` cannot be
|
||||
/// related, we would generate a constraint `'r in ['a, 'b,
|
||||
/// 'static]` for each region `'r` that appears in the hidden type
|
||||
/// (i.e., it must be equal to `'a`, `'b`, or `'static`).
|
||||
///
|
||||
/// `conflict1` and `conflict2` are the two region bounds that we
|
||||
/// detected which were unrelated. They are used for diagnostics.
|
||||
fn generate_member_constraint(
|
||||
&self,
|
||||
concrete_ty: Ty<'tcx>,
|
||||
opaque_defn: &OpaqueTypeDecl<'tcx>,
|
||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
||||
first_own_region: usize,
|
||||
) {
|
||||
// Create the set of choice regions: each region in the hidden
|
||||
// type can be equal to any of the region parameters of the
|
||||
// opaque type definition.
|
||||
let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new(
|
||||
opaque_type_key.substs[first_own_region..]
|
||||
.iter()
|
||||
.filter_map(|arg| match arg.unpack() {
|
||||
GenericArgKind::Lifetime(r) => Some(r),
|
||||
GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
|
||||
})
|
||||
.chain(std::iter::once(self.tcx.lifetimes.re_static))
|
||||
.collect(),
|
||||
);
|
||||
|
||||
concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
|
||||
tcx: self.tcx,
|
||||
op: |r| {
|
||||
self.member_constraint(
|
||||
opaque_type_key.def_id,
|
||||
opaque_defn.definition_span,
|
||||
concrete_ty,
|
||||
r,
|
||||
&choice_regions,
|
||||
)
|
||||
},
|
||||
});
|
||||
}
|
||||
|
||||
/// 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
|
||||
|
|
@ -363,7 +33,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
|
|||
/// purpose of this function is to do that translation.
|
||||
///
|
||||
/// (*) C1 and C2 were introduced in the comments on
|
||||
/// `constrain_opaque_types`. Read that comment for more context.
|
||||
/// `constrain_opaque_type`. Read that comment for more context.
|
||||
///
|
||||
/// # Parameters
|
||||
///
|
||||
|
|
@ -409,83 +79,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
|
|||
}
|
||||
}
|
||||
|
||||
// Visitor that requires that (almost) all regions in the type visited outlive
|
||||
// `least_region`. We cannot use `push_outlives_components` because regions in
|
||||
// closure signatures are not included in their outlives components. We need to
|
||||
// ensure all regions outlive the given bound so that we don't end up with,
|
||||
// say, `ReVar` appearing in a return type and causing ICEs when other
|
||||
// functions end up with region constraints involving regions from other
|
||||
// functions.
|
||||
//
|
||||
// We also cannot use `for_each_free_region` because for closures it includes
|
||||
// the regions parameters from the enclosing item.
|
||||
//
|
||||
// We ignore any type parameters because impl trait values are assumed to
|
||||
// capture all the in-scope type parameters.
|
||||
struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP> {
|
||||
tcx: TyCtxt<'tcx>,
|
||||
op: OP,
|
||||
}
|
||||
|
||||
impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
|
||||
where
|
||||
OP: FnMut(ty::Region<'tcx>),
|
||||
{
|
||||
fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
|
||||
Some(self.tcx)
|
||||
}
|
||||
|
||||
fn visit_binder<T: TypeFoldable<'tcx>>(
|
||||
&mut self,
|
||||
t: &ty::Binder<'tcx, T>,
|
||||
) -> ControlFlow<Self::BreakTy> {
|
||||
t.as_ref().skip_binder().visit_with(self);
|
||||
ControlFlow::CONTINUE
|
||||
}
|
||||
|
||||
fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
|
||||
match *r {
|
||||
// ignore bound regions, keep visiting
|
||||
ty::ReLateBound(_, _) => ControlFlow::CONTINUE,
|
||||
_ => {
|
||||
(self.op)(r);
|
||||
ControlFlow::CONTINUE
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
|
||||
// We're only interested in types involving regions
|
||||
if !ty.flags().intersects(ty::TypeFlags::HAS_POTENTIAL_FREE_REGIONS) {
|
||||
return ControlFlow::CONTINUE;
|
||||
}
|
||||
|
||||
match ty.kind() {
|
||||
ty::Closure(_, ref substs) => {
|
||||
// Skip lifetime parameters of the enclosing item(s)
|
||||
|
||||
substs.as_closure().tupled_upvars_ty().visit_with(self);
|
||||
substs.as_closure().sig_as_fn_ptr_ty().visit_with(self);
|
||||
}
|
||||
|
||||
ty::Generator(_, ref substs, _) => {
|
||||
// Skip lifetime parameters of the enclosing item(s)
|
||||
// Also skip the witness type, because that has no free regions.
|
||||
|
||||
substs.as_generator().tupled_upvars_ty().visit_with(self);
|
||||
substs.as_generator().return_ty().visit_with(self);
|
||||
substs.as_generator().yield_ty().visit_with(self);
|
||||
substs.as_generator().resume_ty().visit_with(self);
|
||||
}
|
||||
_ => {
|
||||
ty.super_visit_with(self);
|
||||
}
|
||||
}
|
||||
|
||||
ControlFlow::CONTINUE
|
||||
}
|
||||
}
|
||||
|
||||
struct ReverseMapper<'tcx> {
|
||||
tcx: TyCtxt<'tcx>,
|
||||
|
||||
|
|
@ -728,235 +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
|
||||
|
|
|
|||
|
|
@ -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,
|
||||
|
|
|
|||
|
|
@ -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};
|
||||
|
|
|
|||
|
|
@ -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,
|
||||
|
|
|
|||
|
|
@ -88,7 +88,6 @@ use rustc_middle::hir::place::{PlaceBase, PlaceWithHirId};
|
|||
use rustc_middle::ty::adjustment;
|
||||
use rustc_middle::ty::{self, Ty};
|
||||
use rustc_span::Span;
|
||||
use rustc_trait_selection::opaque_types::InferCtxtExt as _;
|
||||
use std::ops::Deref;
|
||||
|
||||
// a variation on try that just returns unit
|
||||
|
|
@ -340,8 +339,6 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
|
|||
self.link_fn_params(body.params);
|
||||
self.visit_body(body);
|
||||
self.visit_region_obligations(body_id.hir_id);
|
||||
|
||||
self.constrain_opaque_types();
|
||||
}
|
||||
|
||||
fn visit_region_obligations(&mut self, hir_id: hir::HirId) {
|
||||
|
|
|
|||
|
|
@ -737,7 +737,6 @@ impl Duration {
|
|||
/// # Examples
|
||||
/// ```
|
||||
/// #![feature(duration_checked_float)]
|
||||
///
|
||||
/// use std::time::Duration;
|
||||
///
|
||||
/// let dur = Duration::try_from_secs_f64(2.7);
|
||||
|
|
@ -799,7 +798,6 @@ impl Duration {
|
|||
/// # Examples
|
||||
/// ```
|
||||
/// #![feature(duration_checked_float)]
|
||||
///
|
||||
/// use std::time::Duration;
|
||||
///
|
||||
/// let dur = Duration::try_from_secs_f32(2.7);
|
||||
|
|
@ -1258,7 +1256,6 @@ impl fmt::Debug for Duration {
|
|||
///
|
||||
/// ```
|
||||
/// #![feature(duration_checked_float)]
|
||||
///
|
||||
/// use std::time::Duration;
|
||||
///
|
||||
/// if let Err(e) = Duration::try_from_secs_f32(-1.0) {
|
||||
|
|
|
|||
|
|
@ -66,7 +66,7 @@ assert_eq!(x, 5);
|
|||
This will write the value `5` into the `u64` variable `x`.
|
||||
You can see that the string literal we use to specify instructions is actually a template string.
|
||||
It is governed by the same rules as Rust [format strings][format-syntax].
|
||||
The arguments that are inserted into the template however look a bit different then you may
|
||||
The arguments that are inserted into the template however look a bit different than you may
|
||||
be familiar with. First we need to specify if the variable is an input or an output of the
|
||||
inline assembly. In this case it is an output. We declared this by writing `out`.
|
||||
We also need to specify in what kind of register the assembly expects the variable.
|
||||
|
|
@ -106,7 +106,7 @@ code.
|
|||
Second, we can see that inputs are declared by writing `in` instead of `out`.
|
||||
|
||||
Third, one of our operands has a type we haven't seen yet, `const`.
|
||||
This tells the compiler to expand this argument to value directly inside the assembly template.
|
||||
This tells the compiler to expand this argument to a value directly inside the assembly template.
|
||||
This is only possible for constants and literals.
|
||||
|
||||
Fourth, we can see that we can specify an argument number, or name as in any format string.
|
||||
|
|
|
|||
Loading…
Reference in a new issue