Bring back "pred" syntax for writing predicates for check

This commit reinstates the requirement that the predicate in a
"check" must be a manifest call to a special kind of function
declared with the new "pred" keyword instead of "fn". Preds must
have a boolean return type and can only call other preds; they
can't have any effects (as enforced by the typechecker).
The arguments to a predicate in a check expression must be
slot variables or literals.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/comp/pretty/pprust.rs b/src/comp/pretty/pprust.rs
index 62e6594b..c87a8679 100644
--- a/src/comp/pretty/pprust.rs
+++ b/src/comp/pretty/pprust.rs
@@ -790,7 +790,14 @@ fn print_pat(ps s, &@ast.pat pat) {
 
 fn print_fn(ps s, ast.fn_decl decl, str name,
                    vec[ast.ty_param] typarams) {
-    wrd1(s, "fn");
+    alt (decl.purity) {
+        case (ast.impure_fn) {
+            wrd1(s, "fn");
+        }
+        case (_) {
+            wrd1(s, "pred");
+        }
+    }
     wrd(s.s, name);
     print_type_params(s, typarams);
     popen(s);