1 files changed, 32 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/infer/mod.rs b/compiler/rustc_middle/src/infer/mod.rs
new file mode 100644
index 000000000..38868c210
--- /dev/null
+++ b/compiler/rustc_middle/src/infer/mod.rs
@@ -0,0 +1,32 @@
+pub mod canonical;
+pub mod unify_key;
+
+use crate::ty::Region;
+use crate::ty::{OpaqueTypeKey, Ty};
+use rustc_data_structures::sync::Lrc;
+use rustc_span::Span;
+
+/// Requires that `region` must be equal to one of the regions in `choice_regions`.
+/// We often denote this using the syntax:
+///
+/// ```text
+/// R0 member of [O1..On]
+/// ```
+#[derive(Debug, Clone, HashStable, TypeFoldable, TypeVisitable, Lift)]
+pub struct MemberConstraint<'tcx> {
+    /// The `DefId` and substs of the opaque type causing this constraint.
+    /// Used for error reporting.
+    pub key: OpaqueTypeKey<'tcx>,
+
+    /// The span where the hidden type was instantiated.
+    pub definition_span: Span,
+
+    /// The hidden type in which `member_region` appears: used for error reporting.
+    pub hidden_ty: Ty<'tcx>,
+
+    /// The region `R0`.
+    pub member_region: Region<'tcx>,
+
+    /// The options `O1..On`.
+    pub choice_regions: Lrc<Vec<Region<'tcx>>>,
+}