New upstream version 1.56.0~beta.4+dfsg1

[rustc.git] / compiler / rustc_infer / src / infer / opaque_types.rs

diff --git a/compiler/rustc_infer/src/infer/opaque_types.rs b/compiler/rustc_infer/src/infer/opaque_types.rs
new file mode 100644 (file)
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+++ b/compiler/rustc_infer/src/infer/opaque_types.rs
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+use rustc_data_structures::vec_map::VecMap;
+use rustc_hir as hir;
+use rustc_middle::ty::{OpaqueTypeKey, Ty};
+use rustc_span::Span;
+
+pub type OpaqueTypeMap<'tcx> = VecMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>;
+
+/// Information about the opaque types whose values we
+/// are inferring in this function (these are the `impl Trait` that
+/// appear in the return type).
+#[derive(Copy, Clone, Debug)]
+pub struct OpaqueTypeDecl<'tcx> {
+    /// The opaque type (`ty::Opaque`) for this declaration.
+    pub opaque_type: Ty<'tcx>,
+
+    /// The span of this particular definition of the opaque type. So
+    /// for example:
+    ///
+    /// ```ignore (incomplete snippet)
+    /// type Foo = impl Baz;
+    /// fn bar() -> Foo {
+    /// //          ^^^ This is the span we are looking for!
+    /// }
+    /// ```
+    ///
+    /// In cases where the fn returns `(impl Trait, impl Trait)` or
+    /// other such combinations, the result is currently
+    /// over-approximated, but better than nothing.
+    pub definition_span: Span,
+
+    /// The type variable that represents the value of the opaque type
+    /// that we require. In other words, after we compile this function,
+    /// we will be created a constraint like:
+    ///
+    ///     Foo<'a, T> = ?C
+    ///
+    /// where `?C` is the value of this type variable. =) It may
+    /// naturally refer to the type and lifetime parameters in scope
+    /// in this function, though ultimately it should only reference
+    /// those that are arguments to `Foo` in the constraint above. (In
+    /// other words, `?C` should not include `'b`, even though it's a
+    /// lifetime parameter on `foo`.)
+    pub concrete_ty: Ty<'tcx>,
+
+    /// The origin of the opaque type.
+    pub origin: hir::OpaqueTyOrigin,
+}