diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index a322fcb3fa1..2662d6ef190 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -5824,7 +5824,8 @@ pub fn erase_late_bound_regions<HR>(
 {
     /*!
      * Replace any late-bound regions bound in `value` with `'static`.
-     * Useful in trans.
+     * Useful in trans but also method lookup and a few other places
+     * where precise region relationships are not required.
      */
 
     replace_late_bound_regions(tcx, value, |_, _| ty::ReStatic).0
diff --git a/src/librustc_trans/trans/base.rs b/src/librustc_trans/trans/base.rs
index 39474a99f6d..9c4a532790d 100644
--- a/src/librustc_trans/trans/base.rs
+++ b/src/librustc_trans/trans/base.rs
@@ -519,8 +519,9 @@ pub fn get_res_dtor(ccx: &CrateContext,
         let name = csearch::get_symbol(&ccx.sess().cstore, did);
         let class_ty = ty::lookup_item_type(tcx, parent_id).ty.subst(tcx, substs);
         let llty = type_of_dtor(ccx, class_ty);
-        let dtor_ty = ty::mk_ctor_fn(ccx.tcx(), ast::DUMMY_NODE_ID,
-                                     &[glue::get_drop_glue_type(ccx, t)], ty::mk_nil(ccx.tcx()));
+        let dtor_ty = ty::mk_ctor_fn(ccx.tcx(),
+                                     &[glue::get_drop_glue_type(ccx, t)],
+                                     ty::mk_nil(ccx.tcx()));
         get_extern_fn(ccx,
                       &mut *ccx.externs().borrow_mut(),
                       name.as_slice(),
diff --git a/src/librustc_trans/trans/callee.rs b/src/librustc_trans/trans/callee.rs
index 8e3ae6ee359..cbd0d756f08 100644
--- a/src/librustc_trans/trans/callee.rs
+++ b/src/librustc_trans/trans/callee.rs
@@ -432,6 +432,8 @@ pub fn trans_fn_ref_with_substs(
            substs.repr(tcx));
 
     assert!(substs.types.all(|t| !ty::type_needs_infer(*t)));
+    assert!(substs.types.all(|t| !ty::type_has_escaping_regions(*t)));
+    let substs = substs.erase_regions();
 
     // Load the info for the appropriate trait if necessary.
     match ty::trait_of_item(tcx, def_id) {
@@ -470,8 +472,9 @@ pub fn trans_fn_ref_with_substs(
                                  default methods");
 
                     // Compute the first substitution
-                    let first_subst = make_substs_for_receiver_types(
-                        tcx, &*trait_ref, &*method);
+                    let first_subst =
+                        make_substs_for_receiver_types(tcx, &*trait_ref, &*method)
+                        .erase_regions();
 
                     // And compose them
                     let new_substs = first_subst.subst(tcx, &substs);
@@ -661,7 +664,7 @@ pub fn trans_lang_call<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                                 trans_fn_ref_with_substs_to_callee(bcx,
                                                                    did,
                                                                    0,
-                                                                   subst::Substs::empty())
+                                                                   subst::Substs::trans_empty())
                              },
                              ArgVals(args),
                              dest)
diff --git a/src/librustc_trans/trans/closure.rs b/src/librustc_trans/trans/closure.rs
index 139087507ff..3cb823aec34 100644
--- a/src/librustc_trans/trans/closure.rs
+++ b/src/librustc_trans/trans/closure.rs
@@ -486,7 +486,7 @@ pub fn trans_unboxed_closure<'blk, 'tcx>(
     let llfn = get_or_create_declaration_if_unboxed_closure(
         bcx,
         closure_id,
-        &bcx.fcx.param_substs.substs).unwrap();
+        bcx.fcx.param_substs.substs()).unwrap();
 
     let function_type = (*bcx.tcx().unboxed_closures.borrow())[closure_id]
                                                               .closure_type
diff --git a/src/librustc_trans/trans/common.rs b/src/librustc_trans/trans/common.rs
index d06cfa4a027..21cf3138661 100644
--- a/src/librustc_trans/trans/common.rs
+++ b/src/librustc_trans/trans/common.rs
@@ -191,10 +191,21 @@ pub type ExternMap = FnvHashMap<String, ValueRef>;
 // Here `self_ty` is the real type of the self parameter to this method. It
 // will only be set in the case of default methods.
 pub struct param_substs {
-    pub substs: subst::Substs,
+    substs: subst::Substs,
 }
 
 impl param_substs {
+    pub fn new(substs: subst::Substs) -> param_substs {
+        assert!(substs.types.all(|t| !ty::type_needs_infer(*t)));
+        assert!(substs.types.all(|t| !ty::type_has_params(*t)));
+        assert!(substs.types.all(|t| !ty::type_has_escaping_regions(*t)));
+        param_substs { substs: substs.erase_regions() }
+    }
+
+    pub fn substs(&self) -> &subst::Substs {
+        &self.substs
+    }
+
     pub fn empty() -> param_substs {
         param_substs {
             substs: subst::Substs::trans_empty(),
@@ -822,6 +833,8 @@ pub fn fulfill_obligation(ccx: &CrateContext,
         None => { }
     }
 
+    debug!("trans fulfill_obligation: trait_ref={}", trait_ref.repr(ccx.tcx()));
+
     ty::populate_implementations_for_trait_if_necessary(tcx, trait_ref.def_id);
     let infcx = infer::new_infer_ctxt(tcx);
 
diff --git a/src/librustc_trans/trans/debuginfo.rs b/src/librustc_trans/trans/debuginfo.rs
index e3e36ee53fd..65fd9566760 100644
--- a/src/librustc_trans/trans/debuginfo.rs
+++ b/src/librustc_trans/trans/debuginfo.rs
@@ -1410,7 +1410,7 @@ pub fn create_function_debug_context(cx: &CrateContext,
                                file_metadata: DIFile,
                                name_to_append_suffix_to: &mut String)
                                -> DIArray {
-        let self_type = param_substs.substs.self_ty();
+        let self_type = param_substs.substs().self_ty();
 
         // Only true for static default methods:
         let has_self_type = self_type.is_some();
@@ -1467,7 +1467,7 @@ pub fn create_function_debug_context(cx: &CrateContext,
         }
 
         // Handle other generic parameters
-        let actual_types = param_substs.substs.types.get_slice(subst::FnSpace);
+        let actual_types = param_substs.substs().types.get_slice(subst::FnSpace);
         for (index, &ast::TyParam{ ident, .. }) in generics.ty_params.iter().enumerate() {
             let actual_type = actual_types[index];
             // Add actual type name to <...> clause of function name
diff --git a/src/librustc_trans/trans/expr.rs b/src/librustc_trans/trans/expr.rs
index 2b7c3d0c24f..40a4d6047aa 100644
--- a/src/librustc_trans/trans/expr.rs
+++ b/src/librustc_trans/trans/expr.rs
@@ -329,12 +329,12 @@ fn apply_adjustments<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                                           bcx.ty_to_string(unsized_ty)).as_slice())
             },
             &ty::UnsizeVtable(ty::TyTrait { ref principal, .. }, _) => {
-                let substs = principal.substs.with_self_ty(unsized_ty);
+                let substs = principal.substs.with_self_ty(unsized_ty).erase_regions();
                 let trait_ref =
                     Rc::new(ty::TraitRef { def_id: principal.def_id,
                                            substs: substs });
                 let trait_ref =
-                    trait_ref.subst(bcx.tcx(), &bcx.fcx.param_substs.substs);
+                    trait_ref.subst(bcx.tcx(), bcx.fcx.param_substs.substs());
                 let box_ty = mk_ty(unsized_ty);
                 PointerCast(bcx,
                             meth::get_vtable(bcx, box_ty, trait_ref),
@@ -1122,7 +1122,7 @@ fn trans_rvalue_dps_unadjusted<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                                              .map(|t| (*t).clone())
                                              .unwrap();
                 let trait_ref =
-                    trait_ref.subst(bcx.tcx(), &bcx.fcx.param_substs.substs);
+                    trait_ref.subst(bcx.tcx(), bcx.fcx.param_substs.substs());
                 let datum = unpack_datum!(bcx, trans(bcx, &**val));
                 meth::trans_trait_cast(bcx, datum, expr.id,
                                        trait_ref, dest)
diff --git a/src/librustc_trans/trans/foreign.rs b/src/librustc_trans/trans/foreign.rs
index 3ca37f9e355..f86a0994bf9 100644
--- a/src/librustc_trans/trans/foreign.rs
+++ b/src/librustc_trans/trans/foreign.rs
@@ -536,7 +536,7 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: &CrateContext,
     let _icx = push_ctxt("foreign::build_foreign_fn");
 
     let fnty = ty::node_id_to_type(ccx.tcx(), id);
-    let mty = fnty.subst(ccx.tcx(), &param_substs.substs);
+    let mty = fnty.subst(ccx.tcx(), param_substs.substs());
     let tys = foreign_types_for_fn_ty(ccx, mty);
 
     unsafe { // unsafe because we call LLVM operations
@@ -558,7 +558,7 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: &CrateContext,
         let _icx = push_ctxt("foreign::foreign::build_rust_fn");
         let tcx = ccx.tcx();
         let t = ty::node_id_to_type(tcx, id).subst(
-            ccx.tcx(), &param_substs.substs);
+            ccx.tcx(), param_substs.substs());
 
         let ps = ccx.tcx().map.with_path(id, |path| {
             let abi = Some(ast_map::PathName(special_idents::clownshoe_abi.name));
diff --git a/src/librustc_trans/trans/glue.rs b/src/librustc_trans/trans/glue.rs
index cceea96d4c1..5188ca77350 100644
--- a/src/librustc_trans/trans/glue.rs
+++ b/src/librustc_trans/trans/glue.rs
@@ -287,8 +287,9 @@ fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                                              val, *ty);
         }
 
-        let dtor_ty = ty::mk_ctor_fn(variant_cx.tcx(), ast::DUMMY_NODE_ID,
-                                     &[get_drop_glue_type(bcx.ccx(), t)], ty::mk_nil(bcx.tcx()));
+        let dtor_ty = ty::mk_ctor_fn(bcx.tcx(),
+                                     &[get_drop_glue_type(bcx.ccx(), t)],
+                                     ty::mk_nil(bcx.tcx()));
         let (_, variant_cx) = invoke(variant_cx, dtor_addr, args, dtor_ty, None, false);
 
         variant_cx.fcx.pop_and_trans_custom_cleanup_scope(variant_cx, field_scope);
diff --git a/src/librustc_trans/trans/meth.rs b/src/librustc_trans/trans/meth.rs
index a2510cbfa27..90777afff7e 100644
--- a/src/librustc_trans/trans/meth.rs
+++ b/src/librustc_trans/trans/meth.rs
@@ -137,8 +137,11 @@ pub fn trans_method_callee<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         }) => {
             let trait_ref =
                 Rc::new(trait_ref.subst(bcx.tcx(),
-                                        &bcx.fcx.param_substs.substs));
+                                        bcx.fcx.param_substs.substs()));
             let span = bcx.tcx().map.span(method_call.expr_id);
+            debug!("method_call={} trait_ref={}",
+                   method_call,
+                   trait_ref.repr(bcx.tcx()));
             let origin = fulfill_obligation(bcx.ccx(),
                                             span,
                                             (*trait_ref).clone());
diff --git a/src/librustc_trans/trans/monomorphize.rs b/src/librustc_trans/trans/monomorphize.rs
index 077c1337a44..52aa81fa427 100644
--- a/src/librustc_trans/trans/monomorphize.rs
+++ b/src/librustc_trans/trans/monomorphize.rs
@@ -63,9 +63,8 @@ pub fn monomorphic_fn(ccx: &CrateContext,
         None => ()
     }
 
-    let psubsts = param_substs {
-        substs: (*real_substs).clone(),
-    };
+    debug!("creating param_substs with real_substs={}", real_substs.repr(ccx.tcx()));
+    let psubsts = param_substs::new((*real_substs).clone());
 
     debug!("monomorphic_fn(\
             fn_id={}, \