infer: give access to region variable origins

src/librustc/infer/mod.rs

@@ -25,7 +25,7 @@
 use mir::tcx::LvalueTy;
 use ty::subst::{Kind, Subst, Substs};
 use ty::{TyVid, IntVid, FloatVid};
-use ty::{self, Ty, TyCtxt};
+use ty::{self, RegionVid, Ty, TyCtxt};
 use ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
 use ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use ty::relate::RelateResult;
@@ -1166,6 +1166,21 @@ pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
         self.borrow_region_constraints().take_and_reset_data()
     }
 
+    /// Returns the number of region variables created thus far.
+    pub fn num_region_vars(&self) -> usize {
+        self.borrow_region_constraints().var_origins().len()
+    }
+
+    /// Returns an iterator over all region variables created thus far.
+    pub fn all_region_vars(&self) -> impl Iterator<Item = RegionVid> {
+        self.borrow_region_constraints().var_origins().indices()
+    }
+
+    /// Returns the origin of a given region variable.
+    pub fn region_var_origin(&self, var: RegionVid) -> RegionVariableOrigin {
+        self.borrow_region_constraints().var_origins()[var].clone()
+    }
+
     pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
         self.resolve_type_vars_if_possible(&t).to_string()
     }

src/librustc/infer/region_constraints/mod.rs

@@ -33,7 +33,7 @@
 
 pub struct RegionConstraintCollector<'tcx> {
     /// For each `RegionVid`, the corresponding `RegionVariableOrigin`.
-    pub var_origins: IndexVec<RegionVid, RegionVariableOrigin>,
+    var_origins: IndexVec<RegionVid, RegionVariableOrigin>,
 
     data: RegionConstraintData<'tcx>,
 
@@ -284,6 +284,10 @@ pub fn new() -> RegionConstraintCollector<'tcx> {
         }
     }
 
+    pub fn var_origins(&self) -> &VarOrigins {
+        &self.var_origins
+    }
+
     /// Once all the constraints have been gathered, extract out the final data.
     ///
     /// Not legal during a snapshot.