fix inlining default params issue

streamline.cm

@@ -2809,7 +2809,19 @@ var streamline = function(ir, log) {
       cont_label = label_prefix + "cont"
 
       // Build inlined body with remapping
+      // Unmapped params (e.g. caller passes 1 arg to a 2-param function)
+      // must be explicitly nulled. compress_slots may merge the fresh
+      // slot (base+j) with a previously-live slot that holds a non-null
+      // value, so the default-param jump_not_null preamble would skip
+      // the default assignment and use a stale value instead.
       inlined_body = []
+      j = 0
+      while (j <= callee_func.nr_args) {
+        if (!(j < length(arg_slots) && arg_slots[j] >= 0)) {
+          inlined_body[] = ["null", remap[j], 0, 0]
+        }
+        j = j + 1
+      }
       k = 0
       while (k < length(callee_func.instructions)) {
         cinstr = callee_func.instructions[k]