Move some functions into rustc_infer.
They don't depend on trait selection anymore, so there is no need for an extension trait.
This commit is contained in:
Oli Scherer
parent
849b73b8d9
commit
a8f06b249b
2 changed files with 316 additions and 318 deletions
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@ -1,8 +1,13 @@
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use crate::infer::InferCtxt;
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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_data_structures::vec_map::VecMap;
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use rustc_hir as hir;
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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_middle::ty::subst::GenericArgKind;
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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 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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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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/// Information about the opaque types whose values we
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@ -45,3 +50,312 @@ pub struct OpaqueTypeDecl<'tcx> {
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/// The origin of the opaque type.
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/// The origin of the opaque type.
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pub origin: hir::OpaqueTyOrigin,
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pub origin: hir::OpaqueTyOrigin,
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}
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}
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impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
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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>,
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) -> 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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fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
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match *r {
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// ignore bound regions, keep visiting
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ty::ReLateBound(_, _) => ControlFlow::CONTINUE,
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_ => {
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(self.op)(r);
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ControlFlow::CONTINUE
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}
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}
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}
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fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
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// We're only interested in types involving regions
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if !ty.flags().intersects(ty::TypeFlags::HAS_POTENTIAL_FREE_REGIONS) {
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return ControlFlow::CONTINUE;
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}
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match ty.kind() {
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ty::Closure(_, ref substs) => {
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// Skip lifetime parameters of the enclosing item(s)
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substs.as_closure().tupled_upvars_ty().visit_with(self);
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substs.as_closure().sig_as_fn_ptr_ty().visit_with(self);
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}
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ty::Generator(_, ref substs, _) => {
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// Skip lifetime parameters of the enclosing item(s)
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// Also skip the witness type, because that has no free regions.
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substs.as_generator().tupled_upvars_ty().visit_with(self);
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substs.as_generator().return_ty().visit_with(self);
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substs.as_generator().yield_ty().visit_with(self);
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substs.as_generator().resume_ty().visit_with(self);
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}
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_ => {
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ty.super_visit_with(self);
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}
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}
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ControlFlow::CONTINUE
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}
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}
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@ -1,19 +1,16 @@
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use crate::traits::{self, ObligationCause, PredicateObligation};
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use crate::traits::{self, ObligationCause, PredicateObligation};
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::sync::Lrc;
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use rustc_hir as hir;
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use rustc_hir as hir;
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_infer::infer::error_reporting::unexpected_hidden_region_diagnostic;
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use rustc_infer::infer::error_reporting::unexpected_hidden_region_diagnostic;
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use rustc_infer::infer::opaque_types::OpaqueTypeDecl;
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use rustc_infer::infer::opaque_types::OpaqueTypeDecl;
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use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
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use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
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use rustc_infer::infer::{InferCtxt, InferOk};
|
use rustc_infer::infer::{InferCtxt, InferOk};
|
||||||
use rustc_middle::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder, TypeVisitor};
|
use rustc_middle::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder};
|
||||||
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst};
|
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst};
|
||||||
use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt};
|
use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt};
|
||||||
use rustc_span::Span;
|
use rustc_span::Span;
|
||||||
|
|
||||||
use std::ops::ControlFlow;
|
|
||||||
|
|
||||||
pub trait InferCtxtExt<'tcx> {
|
pub trait InferCtxtExt<'tcx> {
|
||||||
fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
|
fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
|
||||||
&self,
|
&self,
|
||||||
|
|
@ -23,12 +20,6 @@ pub trait InferCtxtExt<'tcx> {
|
||||||
value_span: Span,
|
value_span: Span,
|
||||||
) -> InferOk<'tcx, T>;
|
) -> InferOk<'tcx, T>;
|
||||||
|
|
||||||
fn constrain_opaque_type(
|
|
||||||
&self,
|
|
||||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
|
||||||
opaque_defn: &OpaqueTypeDecl<'tcx>,
|
|
||||||
);
|
|
||||||
|
|
||||||
fn infer_opaque_definition_from_instantiation(
|
fn infer_opaque_definition_from_instantiation(
|
||||||
&self,
|
&self,
|
||||||
opaque_type_key: OpaqueTypeKey<'tcx>,
|
opaque_type_key: OpaqueTypeKey<'tcx>,
|
||||||
|
|
@ -81,236 +72,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
|
||||||
InferOk { value, obligations: instantiator.obligations }
|
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.
|
|
||||||
#[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,
|
|
||||||
};
|
|
||||||
|
|
||||||
// For a case like `impl Foo<'a, 'b>`, 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.
|
|
||||||
|
|
||||||
// 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
|
/// Given the fully resolved, instantiated type for an opaque
|
||||||
/// type, i.e., the value of an inference variable like C1 or C2
|
/// type, i.e., the value of an inference variable like C1 or C2
|
||||||
/// (*), computes the "definition type" for an opaque type
|
/// (*), computes the "definition type" for an opaque type
|
||||||
|
|
@ -372,83 +133,6 @@ 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> {
|
struct ReverseMapper<'tcx> {
|
||||||
tcx: TyCtxt<'tcx>,
|
tcx: TyCtxt<'tcx>,
|
||||||
|
|
||||||
|
|
|
||||||
Loading…
Add table
Add a link
Reference in a new issue