Treat generators the same as closure for escaping lifetimes

Author: matthewjasper

src/librustc/infer/opaque_types/mod.rs

@@ -705,6 +705,23 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ReverseMapper<'cx, 'gcx, 'tcx>
                 self.tcx.mk_closure(def_id, ty::ClosureSubsts { substs })
             }
 
+            ty::Generator(def_id, substs, movability) => {
+                let generics = self.tcx.generics_of(def_id);
+                let substs = self.tcx.mk_substs(substs.substs.iter().enumerate().map(
+                    |(index, &kind)| {
+                        if index < generics.parent_count {
+                            // Accommodate missing regions in the parent kinds...
+                            self.fold_kind_mapping_missing_regions_to_empty(kind)
+                        } else {
+                            // ...but not elsewhere.
+                            self.fold_kind_normally(kind)
+                        }
+                    },
+                ));
+
+                self.tcx.mk_generator(def_id, ty::GeneratorSubsts { substs }, movability)
+            }
+
             _ => ty.super_fold_with(self),
         }
     }

src/test/run-pass/impl-trait/lifetimes.rs

@@ -1,6 +1,7 @@
 // run-pass
 
 #![allow(warnings)]
+#![feature(generators)]
 
 use std::fmt::Debug;
 
@@ -112,6 +113,11 @@ impl<'unnecessary_lifetime> MyVec {
     fn iter_doesnt_capture_unnecessary_lifetime<'s>(&'s self) -> impl Iterator<Item = &'s u8> {
         self.0.iter().flat_map(|inner_vec| inner_vec.iter())
     }
+
+    fn generator_doesnt_capture_unnecessary_lifetime<'s: 's>() -> impl Sized {
+        || yield
+    }
 }
 
+
 fn main() {}