Attempt to call shrink_to_fit at appropriate points to model potential space improvemetns in VecPerParamSpace.

Author: pnkfelix

src/librustc/middle/subst.rs

@@ -271,6 +271,12 @@ impl<T> VecPerParamSpace<T> {
         }
     }
 
+    pub fn shrink_to_fit(&mut self) {
+        self.vecs.mut0().shrink_to_fit();
+        self.vecs.mut1().shrink_to_fit();
+        self.vecs.mut2().shrink_to_fit();
+    }
+
     pub fn params_from_type(types: Vec<T>) -> VecPerParamSpace<T> {
         VecPerParamSpace::empty().with_vec(TypeSpace, types)
     }

src/librustc/middle/ty.rs

@@ -4615,13 +4615,15 @@ pub fn construct_parameter_environment(
         push_types_from_defs(tcx, &mut types, space,
                              generics.types.get_vec(space));
     }
+    types.shrink_to_fit();
 
     // map bound 'a => free 'a
     let mut regions = VecPerParamSpace::empty();
     for &space in subst::ParamSpace::all().iter() {
         push_region_params(&mut regions, space, free_id,
                            generics.regions.get_vec(space));
     }
+    regions.shrink_to_fit();
 
     let free_substs = Substs {
         types: types,
@@ -4637,6 +4639,7 @@ pub fn construct_parameter_environment(
         push_bounds_from_defs(tcx, &mut bounds, space, &free_substs,
                               generics.types.get_vec(space));
     }
+    bounds.shrink_to_fit();
 
     debug!("construct_parameter_environment: free_id={} \
            free_subst={} \