Serialize constraints in types (literal arguments still not supported)

This involved, in part, changing the ast::def type so that a def_fn
has a "purity" field. This lets the typechecker determine whether
functions defined in other crates are pure.

It also required updating some error messages in tests. As a test
for cross-crate constrained functions, I added a safe_slice function
to std::str (slice(), with one of the asserts replaced with a
function precondition) and some test cases (various versions of
fn-constraint.rs) that call it. Also, I changed "fn" to "pred" for
some of the boolean functions in std::uint.

15 files changed, 147 insertions, 113 deletions

diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index 359244441b5..14bc0e8532e 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -27,7 +27,7 @@ fn local_def(node_id id) -> def_id {
 type ty_param = ident;
 
 tag def {
-    def_fn(def_id);
+    def_fn(def_id, purity);
     def_obj(def_id);
     def_obj_field(def_id);
     def_mod(def_id);
@@ -54,7 +54,7 @@ fn variant_def_ids(&def d) -> tup(def_id, def_id) {
 
 fn def_id_of_def(def d) -> def_id {
     alt (d) {
-        case (def_fn(?id)) { ret id; }
+        case (def_fn(?id,_)) { ret id; }
         case (def_obj(?id)) { ret id; }
         case (def_obj_field(?id)) { ret id; }
         case (def_mod(?id)) { ret id; }
diff --git a/src/comp/front/creader.rs b/src/comp/front/creader.rs
index f118775d3f8..b297f062de9 100644
--- a/src/comp/front/creader.rs
+++ b/src/comp/front/creader.rs
@@ -56,13 +56,22 @@ fn next(@pstate st) -> u8 {
 }
 
 fn parse_ident(@pstate st, str_def sd, char last) -> ast::ident {
+    fn is_last(char b, char c) -> bool {
+        ret c == b;
+    }
+    ret parse_ident_(st, sd, bind is_last(last, _));
+}
+
+fn parse_ident_(@pstate st, str_def sd, fn(char) -> bool is_last)
+    -> ast::ident {
     auto res = "";
-    while (peek(st) as char != last) {
+    while (! is_last(peek(st) as char)) {
         res += str::unsafe_from_byte(next(st));
     }
     ret res;
 }
 
+
 fn parse_ty_data(vec[u8] data, int crate_num, uint pos, uint len, str_def sd,
                  ty::ctxt tcx) -> ty::t {
     auto st =
@@ -85,40 +94,59 @@ fn parse_constrs(@pstate st, str_def sd) -> vec[@ty::constr_def] {
             do  {
                 auto ignore = next(st);
                 vec::push(res, parse_constr(st, sd));
-            } while (peek(st) as char == ',')
+            } while (peek(st) as char == ';')
         }
         case (_) { }
     }
     ret res;
 }
 
+fn parse_path(@pstate st, str_def sd) -> ast::path {
+    let vec[ast::ident] idents = [];
+    fn is_last(char c) -> bool {
+        ret (c == '(' || c == ':');
+    }
+    idents += [parse_ident_(st, sd, is_last)];
+    while (true) {
+        alt (peek(st) as char) {
+            case (':') {
+                auto ignore = next(st);
+                ignore = next(st);
+            }
+            case (?c) {
+                if (c == '(') {
+                    ret respan(rec(lo=0u, hi=0u),
+                               rec(idents=idents, types=[]));
+                }
+                else {
+                    idents += [parse_ident_(st, sd, is_last)];
+                }
+            }
+        }
+    }
+    fail "parse_path: ill-formed path";
+}
+
 fn parse_constr(@pstate st, str_def sd) -> @ty::constr_def {
-    st.tcx.sess.unimpl("Reading constraints " + " isn't implemented");
-    /*
     let vec[@ast::constr_arg] args = [];
-    auto sp = rec(lo=0u,hi=0u); // FIXME
-    let vec[ast::ident] ids = [];
-    let vec[@ast::ty] tys = [];
-    let ast::path pth = respan(sp,
-                               rec(idents=ids, types=tys)); // FIXME
-    let ast::ident p1 = parse_ident(st, sd, '(');
-    log_err("ignore=");
-    log_err(p1);
+    auto sp = rec(lo=0u,hi=0u); // FIXME: use a real span
+    let ast::path pth = parse_path(st, sd);
     let char ignore = next(st) as char;
     assert(ignore as char == '(');
     auto def = parse_def(st, sd);
     do {
         alt (peek(st) as char) {
             case ('*') {
-                auto ignore = next(st);
+                st.pos += 1u;
                 args += [@respan(sp, ast::carg_base)];
             }
             case (?c) {
-                log_err("c =");
-                log_err(str::from_bytes([c as u8]));
-                if (may_begin_ident(c)) {
-                    auto id = parse_ident(st, sd, ',');
-                    args += [@respan(sp, ast::carg_ident(id))];
+                /* how will we disambiguate between
+                 an arg index and a lit argument? */
+                if (c >= '0' && c <= '9') {
+                    // FIXME
+                    args += [@respan(sp, ast::carg_ident((c as uint) - 48u))];
+                    ignore = next(st) as char;
                 }
                 else {
                     log_err("Lit args are unimplemented");
@@ -132,10 +160,10 @@ fn parse_constr(@pstate st, str_def sd) -> @ty::constr_def {
                 */
             }
         }
-    } while (next(st) as char == ',');
-    ignore = next(st) as char;
-    */
-
+        ignore = next(st) as char;
+    } while (ignore == ';');
+    assert(ignore == ')');
+    ret @respan(sp, rec(path=pth, args=args, id=def));
 }
 
 fn parse_ty(@pstate st, str_def sd) -> ty::t {
@@ -333,7 +361,7 @@ fn parse_ty_fn(@pstate st, str_def sd) ->
         }
         inputs += [rec(mode=mode, ty=parse_ty(st, sd))];
     }
-    st.pos = st.pos + 1u;
+    st.pos += 1u; // eat the ']'
     auto cs = parse_constrs(st, sd);
     auto res = parse_ty_or_bang(st, sd);
     alt (res) {
@@ -641,6 +669,7 @@ fn kind_has_type_params(u8 kind_ch) -> bool {
     ret alt (kind_ch as char) {
             case ('c') { false }
             case ('f') { true }
+            case ('p') { true }
             case ('F') { true }
             case ('y') { true }
             case ('o') { true }
@@ -669,7 +698,8 @@ fn lookup_def(int cnum, vec[u8] data, &ast::def_id did_) -> ast::def {
     auto def =
         alt (kind_ch as char) {
             case ('c') { ast::def_const(did) }
-            case ('f') { ast::def_fn(did) }
+            case ('f') { ast::def_fn(did, ast::impure_fn) }
+            case ('p') { ast::def_fn(did, ast::pure_fn) }
             case ('F') { ast::def_native_fn(did) }
             case ('y') { ast::def_ty(did) }
             case ('o') { ast::def_obj(did) }
@@ -781,6 +811,7 @@ fn item_kind_to_str(u8 kind) -> str {
     alt (kind as char) {
         case ('c') { ret "const"; }
         case ('f') { ret "fn"; }
+        case ('p') { ret "pred"; }
         case ('F') { ret "native fn"; }
         case ('y') { ret "type"; }
         case ('o') { ret "obj"; }
diff --git a/src/comp/middle/metadata.rs b/src/comp/middle/metadata.rs
index c438ddef011..ef3ddcf016c 100644
--- a/src/comp/middle/metadata.rs
+++ b/src/comp/middle/metadata.rs
@@ -264,34 +264,37 @@ mod Encode {
             enc_ty(w, cx, arg.ty);
         }
         w.write_char(']');
-        alt (cf) {
-            case (noreturn) { w.write_char('!'); }
-            case (_) { enc_ty(w, cx, out); }
-        }
         auto colon = true;
         for (@ty::constr_def c in constrs) {
             if (colon) {
                 w.write_char(':');
                 colon = false;
-            } else { w.write_char(','); }
+            } else { w.write_char(';'); }
             enc_constr(w, cx, c);
         }
+        alt (cf) {
+            case (noreturn) { w.write_char('!'); }
+            case (_) { enc_ty(w, cx, out); }
+        }
+
     }
     fn enc_constr(&io::writer w, &@ctxt cx, &@ty::constr_def c) {
         w.write_str(path_to_str(c.node.path));
         w.write_char('(');
-        // FIXME
-        //   w.write_str(cx.ds(c.node.id));
-
-        auto comma = false;
+        w.write_str(cx.ds(c.node.id));
+        w.write_char('|');
+        auto semi = false;
         for (@constr_arg a in c.node.args) {
-            if (comma) { w.write_char(','); } else { comma = true; }
+            if (semi) { w.write_char(';'); } else { semi = true; }
             alt (a.node) {
                 case (carg_base) { w.write_char('*'); }
-                case (carg_ident(?i)) { w.write_uint(i); }
+                case (carg_ident(?i)) { 
+                    w.write_uint(i);
+                }
                 case (carg_lit(?l)) { w.write_str(lit_to_str(l)); }
             }
         }
+        w.write_char(')');
     }
 }
 
@@ -506,10 +509,12 @@ fn encode_info_for_item(@trans::crate_ctxt cx, &ebml::writer ebml_w,
             encode_symbol(cx, ebml_w, item.id);
             ebml::end_tag(ebml_w);
         }
-        case (item_fn(_, ?tps)) {
+        case (item_fn(?fd, ?tps)) {
             ebml::start_tag(ebml_w, tag_items_data_item);
             encode_def_id(ebml_w, local_def(item.id));
-            encode_kind(ebml_w, 'f' as u8);
+            encode_kind(ebml_w, alt (fd.decl.purity) {
+                                  case (pure_fn) { 'p' }
+                                  case (impure_fn) { 'f' } } as u8);
             encode_type_param_count(ebml_w, tps);
             encode_type(cx, ebml_w, trans::node_id_type(cx, item.id));
             encode_symbol(cx, ebml_w, item.id);
diff --git a/src/comp/middle/resolve.rs b/src/comp/middle/resolve.rs
index 7bc9d9b8018..180b422d5e5 100644
--- a/src/comp/middle/resolve.rs
+++ b/src/comp/middle/resolve.rs
@@ -412,7 +412,7 @@ fn resolve_constr(@env e, node_id id, &@ast::constr c, &scopes sc,
         lookup_path_strict(*e, sc, c.span, c.node.path.node.idents, ns_value);
     if (option::is_some(new_def)) {
         alt (option::get(new_def)) {
-            case (ast::def_fn(?pred_id)) {
+            case (ast::def_fn(?pred_id, _)) {
                 let ty::constr_general[uint] c_ =
                     rec(path=c.node.path, args=c.node.args, id=pred_id);
                 let ty::constr_def new_constr = respan(c.span, c_);
@@ -799,9 +799,9 @@ fn found_def_item(&@ast::item i, namespace ns) -> option::t[def] {
                 ret some(ast::def_const(local_def(i.id)));
             }
         }
-        case (ast::item_fn(_, _)) {
+        case (ast::item_fn(?f, _)) {
             if (ns == ns_value) {
-                ret some(ast::def_fn(local_def(i.id)));
+                ret some(ast::def_fn(local_def(i.id), f.decl.purity));
             }
         }
         case (ast::item_mod(_)) {
@@ -1122,7 +1122,7 @@ fn index_nmod(&ast::native_mod md) -> mod_index {
 // External lookups
 fn ns_for_def(def d) -> namespace {
     ret alt (d) {
-            case (ast::def_fn(?id)) { ns_value }
+            case (ast::def_fn(?id, _)) { ns_value }
             case (ast::def_obj(?id)) { ns_value }
             case (ast::def_obj_field(?id)) { ns_value }
             case (ast::def_mod(?id)) { ns_module }
diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index 9468ef8fa48..9f6d47b90d4 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -4681,7 +4681,7 @@ fn trans_path(&@block_ctxt cx, &ast::path p, ast::node_id id) -> lval_result {
             assert (cx.fcx.llobjfields.contains_key(did._1));
             ret lval_mem(cx, cx.fcx.llobjfields.get(did._1));
         }
-        case (ast::def_fn(?did)) {
+        case (ast::def_fn(?did, _)) {
             auto tyt = ty::lookup_item_type(cx.fcx.lcx.ccx.tcx, did);
             ret lval_generic_fn(cx, tyt, did, id);
         }
diff --git a/src/comp/middle/tstate/auxiliary.rs b/src/comp/middle/tstate/auxiliary.rs
index fea8a101f9f..d2b6a249122 100644
--- a/src/comp/middle/tstate/auxiliary.rs
+++ b/src/comp/middle/tstate/auxiliary.rs
@@ -537,7 +537,7 @@ fn node_id_for_constr(ty::ctxt tcx, node_id t) -> node_id {
         case (none) {
             tcx.sess.bug("node_id_for_constr: bad node_id " + istr(t));
         }
-        case (some(def_fn(?i))) { ret i._1; }
+        case (some(def_fn(?i,_))) { ret i._1; }
         case (_) {
             tcx.sess.bug("node_id_for_constr: pred is not a function");
         }
diff --git a/src/comp/middle/ty.rs b/src/comp/middle/ty.rs
index 37435824fa3..b38c9237cef 100644
--- a/src/comp/middle/ty.rs
+++ b/src/comp/middle/ty.rs
@@ -2610,7 +2610,7 @@ fn substitute_type_params(&ctxt cx, vec[ty::t] substs, t typ) -> t {
 
 fn def_has_ty_params(&ast::def def) -> bool {
     alt (def) {
-        case (ast::def_fn(_)) { ret true; }
+        case (ast::def_fn(_,_)) { ret true; }
         case (ast::def_obj(_)) { ret true; }
         case (ast::def_obj_field(_)) { ret false; }
         case (ast::def_mod(_)) { ret false; }
diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index 48fe6aee529..3a33e64b6b9 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -48,13 +48,10 @@ import middle::tstate::ann::ts_ann;
 
 type ty_table = hashmap[ast::def_id, ty::t];
 
-type fn_purity_table = hashmap[ast::def_id, ast::purity];
-
 type obj_info = rec(vec[ast::obj_field] obj_fields, ast::node_id this_obj);
 
 type crate_ctxt =
     rec(mutable vec[obj_info] obj_infos,
-        @fn_purity_table fn_purity_table,
         ty::ctxt tcx);
 
 type fn_ctxt =
@@ -91,7 +88,9 @@ fn ty_param_count_and_ty_for_def(&@fn_ctxt fcx, &span sp, &ast::def defn) ->
             auto typ = ty::mk_var(fcx.ccx.tcx, fcx.locals.get(id._1));
             ret tup(0u, typ);
         }
-        case (ast::def_fn(?id)) { ret ty::lookup_item_type(fcx.ccx.tcx, id); }
+        case (ast::def_fn(?id, _)) {
+            ret ty::lookup_item_type(fcx.ccx.tcx, id);
+        }
         case (ast::def_native_fn(?id)) {
             ret ty::lookup_item_type(fcx.ccx.tcx, id);
         }
@@ -1271,51 +1270,24 @@ fn require_impure(&session::session sess, &ast::purity f_purity, &span sp) {
     }
 }
 
-fn get_function_purity(@crate_ctxt ccx, &ast::def_id d_id) -> ast::purity {
-    let option::t[ast::purity] o = ccx.fn_purity_table.find(d_id);
-    ret from_maybe[ast::purity](ast::impure_fn, o);
-}
-
 fn require_pure_call(@crate_ctxt ccx, &ast::purity caller_purity,
                      &@ast::expr callee, &span sp) {
     alt (caller_purity) {
         case (ast::impure_fn) { ret; }
         case (ast::pure_fn) {
-            alt (callee.node) {
-                case (ast::expr_path(_)) {
-                    auto d_id;
-                    alt (ccx.tcx.def_map.get(callee.id)) {
-                        case (ast::def_fn(?_d_id)) { d_id = _d_id; }
-                    }
-                    alt (get_function_purity(ccx, d_id)) {
-                        case (ast::pure_fn) { ret; }
-                        case (_) {
-                            ccx.tcx.sess.span_fatal(sp,
-                                                  "Pure function calls \
-                                                   impure function");
-                        }
-                    }
+            alt (ccx.tcx.def_map.get(callee.id)) {
+                case (ast::def_fn(_, ast::pure_fn)) {
+                    ret;
                 }
                 case (_) {
                     ccx.tcx.sess.span_fatal(sp,
-                                          "Pure function calls \
-                                           unknown function");
+                     "Pure function calls function not known to be pure");
                 }
             }
         }
     }
 }
 
-fn require_pure_function(@crate_ctxt ccx, &ast::def_id d_id, &span sp) {
-    alt (get_function_purity(ccx, d_id)) {
-        case (ast::impure_fn) {
-            ccx.tcx.sess.span_fatal(sp,
-                                  "Found non-predicate in check expression");
-        }
-        case (_) { ret; }
-    }
-}
-
 fn check_expr(&@fn_ctxt fcx, &@ast::expr expr) {
     // fcx.ccx.tcx.sess.span_warn(expr.span, "typechecking expr " +
     //                                pretty::pprust::expr_to_str(expr));
@@ -1428,9 +1400,15 @@ fn check_expr(&@fn_ctxt fcx, &@ast::expr expr) {
                 case (ast::expr_call(?operator, ?operands)) {
                     alt (operator.node) {
                         case (ast::expr_path(?oper_name)) {
-                            auto d_id;
                             alt (fcx.ccx.tcx.def_map.get(operator.id)) {
-                                case (ast::def_fn(?_d_id)) { d_id = _d_id; }
+                                case (ast::def_fn(?_d_id, ast::pure_fn)) { 
+                                    // do nothing
+                                }
+                                case (_) {
+                                    fcx.ccx.tcx.sess.span_fatal(operator.span,
+                                      "non-predicate as operator \
+                                       in constraint");
+                                }
                             }
                             for (@ast::expr operand in operands) {
                                 if (!ast::is_constraint_arg(operand)) {
@@ -1439,7 +1417,6 @@ fn check_expr(&@fn_ctxt fcx, &@ast::expr expr) {
                                     fcx.ccx.tcx.sess.span_fatal(e.span, s);
                                 }
                             }
-                            require_pure_function(fcx.ccx, d_id, e.span);
                         }
                         case (_) {
                             auto s = "In a constraint, expected the \
@@ -2193,14 +2170,15 @@ fn get_obj_info(&@crate_ctxt ccx) -> option::t[obj_info] {
 fn ast_constr_to_constr(ty::ctxt tcx, &@ast::constr c)
     -> @ty::constr_def {
     alt (tcx.def_map.find(c.node.id)) {
-        case (some(ast::def_fn(?pred_id))) {
+        case (some(ast::def_fn(?pred_id, ast::pure_fn))) {
             ret @respan(c.span, rec(path=c.node.path, args=c.node.args,
                                     id=pred_id));
         }
         case (_) {
             tcx.sess.span_fatal(c.span, "Predicate "
                               + path_to_str(c.node.path)
-                              + " is unbound or bound to a non-function");
+                              + " is unbound or bound to a non-function or an\
+                                impure function");
         }
     }
 }
@@ -2372,30 +2350,12 @@ fn check_item(@crate_ctxt ccx, &@ast::item it) {
     }
 }
 
-fn mk_fn_purity_table(&@ast::crate crate) -> @fn_purity_table {
-    auto res = @new_def_hash[ast::purity]();
-    fn do_one(@fn_purity_table t, &@ast::item i) {
-        alt (i.node) {
-            case (ast::item_fn(?f, _)) {
-                t.insert(local_def(i.id), f.decl.purity);
-            }
-            case (_) { }
-        }
-    }
-    auto do_one_fn = bind do_one(res, _);
-    auto v = walk::default_visitor();
-    auto add_fn_entry_visitor = rec(visit_item_post=do_one_fn with v);
-    walk::walk_crate(add_fn_entry_visitor, *crate);
-    ret res;
-}
-
 fn check_crate(&ty::ctxt tcx, &@ast::crate crate) {
     collect::collect_item_types(tcx, crate);
     let vec[obj_info] obj_infos = [];
-    auto fpt = mk_fn_purity_table(crate); // use a variation on collect
 
     auto ccx =
-        @rec(mutable obj_infos=obj_infos, fn_purity_table=fpt, tcx=tcx);
+        @rec(mutable obj_infos=obj_infos, tcx=tcx);
     auto visit =
         rec(visit_item_pre=bind check_item(ccx, _)
             with walk::default_visitor());
diff --git a/src/lib/str.rs b/src/lib/str.rs
index 51b876e3253..3ad63093ddc 100644
--- a/src/lib/str.rs
+++ b/src/lib/str.rs
@@ -1,6 +1,7 @@
 
 import rustrt::sbuf;
 import vec::rustrt::vbuf;
+import uint::le;
 export sbuf;
 export rustrt;
 export eq;
@@ -45,6 +46,7 @@ export split;
 export concat;
 export connect;
 export to_upper;
+export safe_slice;
 
 native "rust" mod rustrt {
     type sbuf;
@@ -381,6 +383,12 @@ fn slice(str s, uint begin, uint end) -> str {
     ret rustrt::str_slice(s, begin, end);
 }
 
+fn safe_slice(str s, uint begin, uint end) : le(begin, end) -> str {
+    assert (end <= str::byte_len(s)); // would need some magic to
+                                      // make this a precondition
+    ret rustrt::str_slice(s, begin, end);
+}
+
 fn shift_byte(&mutable str s) -> u8 {
     auto len = byte_len(s);
     assert (len > 0u);
diff --git a/src/lib/uint.rs b/src/lib/uint.rs
index 27c0a0e458e..ca632914a45 100644
--- a/src/lib/uint.rs
+++ b/src/lib/uint.rs
@@ -10,17 +10,17 @@ fn div(uint x, uint y) -> uint { ret x / y; }
 
 fn rem(uint x, uint y) -> uint { ret x % y; }
 
-fn lt(uint x, uint y) -> bool { ret x < y; }
+pred lt(uint x, uint y) -> bool { ret x < y; }
 
-fn le(uint x, uint y) -> bool { ret x <= y; }
+pred le(uint x, uint y) -> bool { ret x <= y; }
 
-fn eq(uint x, uint y) -> bool { ret x == y; }
+pred eq(uint x, uint y) -> bool { ret x == y; }
 
-fn ne(uint x, uint y) -> bool { ret x != y; }
+pred ne(uint x, uint y) -> bool { ret x != y; }
 
-fn ge(uint x, uint y) -> bool { ret x >= y; }
+pred ge(uint x, uint y) -> bool { ret x >= y; }
 
-fn gt(uint x, uint y) -> bool { ret x > y; }
+pred gt(uint x, uint y) -> bool { ret x > y; }
 
 fn max(uint x, uint y) -> uint { if (x > y) { ret x; } ret y; }
 
diff --git a/src/test/compile-fail/fn-constraint.rs b/src/test/compile-fail/fn-constraint.rs
new file mode 100644
index 00000000000..85f3c8c7988
--- /dev/null
+++ b/src/test/compile-fail/fn-constraint.rs
@@ -0,0 +1,9 @@
+// error-pattern: Unsatisfied precondition constraint (for example, le(a, b)
+use std;
+import std::str::*;
+
+fn main() {
+  let uint a = 4u;
+  let uint b = 1u;
+  log_err (safe_slice("kitties", a, b));
+}
\ No newline at end of file
diff --git a/src/test/compile-fail/impure-pred.rs b/src/test/compile-fail/impure-pred.rs
index 54b9ee8831c..5c046ed26da 100644
--- a/src/test/compile-fail/impure-pred.rs
+++ b/src/test/compile-fail/impure-pred.rs
@@ -1,5 +1,5 @@
 // -*- rust -*-
-// error-pattern: impure function
+// error-pattern: Pure function calls function not known to be pure
 
 fn g() -> () {}
 
diff --git a/src/test/compile-fail/not-pred-args.rs b/src/test/compile-fail/not-pred-args.rs
index 6e810e5227c..0425c1a67e5 100644
--- a/src/test/compile-fail/not-pred-args.rs
+++ b/src/test/compile-fail/not-pred-args.rs
@@ -2,7 +2,7 @@
 
 // error-pattern: Constraint args must be
 
-fn f(int q) -> bool { ret true; }
+pred f(int q) -> bool { ret true; }
 
 fn main() {
 // should fail to typecheck, as pred args must be slot variables or literals
diff --git a/src/test/run-fail/fn-constraint.rs b/src/test/run-fail/fn-constraint.rs
new file mode 100644
index 00000000000..3f7933465b7
--- /dev/null
+++ b/src/test/run-fail/fn-constraint.rs
@@ -0,0 +1,11 @@
+// error-pattern:Predicate le(a, b) failed
+use std;
+import std::str::*;
+import std::uint::le;
+
+fn main() {
+  let uint a = 4u;
+  let uint b = 1u;
+  check le(a, b);
+  log_err (safe_slice("kitties", a, b));
+}
\ No newline at end of file
diff --git a/src/test/run-pass/fn-constraint.rs b/src/test/run-pass/fn-constraint.rs
new file mode 100644
index 00000000000..1e55fc45445
--- /dev/null
+++ b/src/test/run-pass/fn-constraint.rs
@@ -0,0 +1,10 @@
+use std;
+import std::str::*;
+import std::uint::*;
+
+fn main() {
+  let uint a = 1u;
+  let uint b = 4u;
+  check le(a, b);
+  log (safe_slice("kitties", a, b)); 
+}
\ No newline at end of file