rustc: Don't recurse in seq_preconds. Consumes too much stack

src/rustc/middle/tstate/bitvectors.rs

@@ -82,6 +82,9 @@ fn seq_preconds(fcx: fn_ctxt, pps: [pre_and_post]) -> precond {
 
     fn seq_preconds_go(fcx: fn_ctxt, pps: [pre_and_post], first: pre_and_post)
        -> precond {
+        let mut pps = pps;
+        let mut first = first;
+        loop {
             let sz: uint = vec::len(pps);
             if sz >= 1u {
                 let second = pps[0];
@@ -92,12 +95,12 @@ fn seq_preconds(fcx: fn_ctxt, pps: [pre_and_post]) -> precond {
                 union(next_first, second_pre);
                 let next_first_post = clone(first.postcondition);
                 seq_tritv(next_first_post, second.postcondition);
-            ret seq_preconds_go(fcx, vec::slice(pps, 1u, sz),
-                                @{precondition: next_first,
-                                  postcondition: next_first_post});
+                pps = vec::slice(pps, 1u, sz);
+                first = @{precondition: next_first,
+                          postcondition: next_first_post};
             } else { ret first.precondition; }
         }
-
+    }
 
     if sz >= 1u {
         let first = pps[0];