---

yaml
---
r: 2213
b: refs/heads/master
c: 485399a
h: refs/heads/master
i:
  2211: 3003dab
v: v3

Author: graydon

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1b9e6b3ad28ce934f993f1bb8227f40d6f6d25e2
+refs/heads/master: 485399a8d5de8a8bb759feacd9e4915055e51cb5

trunk/src/comp/middle/ty.rs

@@ -1391,6 +1391,34 @@ fn type_contains_vars(@type_store tystore, t typ) -> bool {
     ret *flag;
 }
 
+fn type_contains_params(@type_store tystore, t typ) -> bool {
+    fn checker(@type_store tystore, @mutable bool flag, t typ) {
+        alt (struct(tystore, typ)) {
+            case (ty_param(_)) { *flag = true; }
+            case (_) { /* fall through */ }
+        }
+    }
+
+    let @mutable bool flag = @mutable false;
+    auto f = bind checker(tystore, flag, _);
+    walk_ty(tystore, f, typ);
+    ret *flag;
+}
+
+fn type_contains_bound_params(@type_store tystore, t typ) -> bool {
+    fn checker(@type_store tystore, @mutable bool flag, t typ) {
+        alt (struct(tystore, typ)) {
+            case (ty_bound_param(_)) { *flag = true; }
+            case (_) { /* fall through */ }
+        }
+    }
+
+    let @mutable bool flag = @mutable false;
+    auto f = bind checker(tystore, flag, _);
+    walk_ty(tystore, f, typ);
+    ret *flag;
+}
+
 // Type accessors for substructures of types
 
 fn ty_fn_args(@type_store tystore, t fty) -> vec[arg] {
@@ -2495,6 +2523,9 @@ fn type_err_to_str(&ty.type_err err) -> str {
 fn substitute_type_params(@type_store tystore,
                           vec[t] bindings,
                           t typ) -> t {
+    if (!type_contains_bound_params(tystore, typ)) {
+        ret typ;
+    }
     fn replacer(@type_store tystore, vec[t] bindings, t typ) -> t {
         alt (struct(tystore, typ)) {
             case (ty_bound_param(?param_index)) {
@@ -2510,6 +2541,9 @@ fn substitute_type_params(@type_store tystore,
 
 // Converts type parameters in a type to bound type parameters.
 fn bind_params_in_type(@type_store tystore, t typ) -> t {
+    if (!type_contains_params(tystore, typ)) {
+        ret typ;
+    }
     fn binder(@type_store tystore, t typ) -> t {
         alt (struct(tystore, typ)) {
             case (ty_bound_param(?index)) {