Fix infinite recursion on defn and derivatives on invalid

input.

src/compiler/boot.dst

@@ -14,12 +14,14 @@
 (def defn :macro
  "Define a function"
   (fn [name & more]
+   (def len (length more))
    (def fstart (fn recur [i]
     (def ith (ast-unwrap1 (get more i)))
     (def t (type ith))
     (def tuple? (= t :tuple))
     (def array? (= t :array))
-    (if (if tuple? tuple? array?) i (recur (+ i 1)))))
+    (if (if tuple? tuple? array?) i 
+     (if (< i len) (recur (+ i 1))))))
    (def start (fstart 0))
    (def fnbody (tuple-prepend (tuple-prepend (tuple-slice more start) name) 'fn))
    (def formargs (array-concat @['def name] (array-slice more 0 start) @[fnbody]))
@@ -475,22 +477,6 @@ the predicate, and abort on first failiure."
  [pred ind t]
  (drop-until (complement pred) ind t))
 
-(defn zip
- [& seqs]
- (def lens (length seqs))
- (def ret @[])
- (if (= 0 lens) (error "expected at least 1 sequence"))
- (var minlen (length (get seqs 0)))
- (for [j 1 lens]
-  (def sl (length (get seqs j)))
-  (if (< sl minlen) (:= minlen sl)))
- (for [i 0 minlen]
-  (def accum @[])
-  (for [j 0 lens]
-   (array-push accum (get seqs j i)))
-  (array-push ret (apply1 tuple accum)))
- (apply1 tuple ret))
-
 (defn juxt*
   [& funs]
   (def len (length funs))
@@ -509,6 +495,9 @@ the predicate, and abort on first failiure."
  (tuple 'fn (tuple '& $args) (apply1 tuple parts)))
 
 (defmacro ->
+ "Threading macro. Inserts x as the second value in the first form
+in form, and inserts the modified firsts form into the second form
+in the same manner, and so on. Useful for expressing pipelines of data."
  [x & forms]
  (defn fop [last nextform]
   (def n (ast-unwrap1 nextform))
@@ -520,6 +509,9 @@ the predicate, and abort on first failiure."
  (reduce fop x forms))
 
 (defmacro ->>
+ "Threading macro. Inserts x as the last value in the first form
+in form, and inserts the modified firsts form into the second form
+in the same manner, and so on. Useful for expressing pipelines of data."
  [x & forms]
  (defn fop [last nextform]
   (def n (ast-unwrap1 nextform))

src/compiler/compile.c

@@ -830,7 +830,8 @@ recur:
                                     x = dst_resume(f, dst_tuple_length(tup) - 1, tup + 1);
                                     dst_gcunlock(lock);
                                     if (f->status == DST_FIBER_ERROR || f->status == DST_FIBER_DEBUG) {
-                                        dstc_cerror(c, ast, "error in macro expansion");
+                                        const uint8_t *es = dst_formatc("error in macro expansion: %V", x);
+                                        dstc_error(c, ast, es);
                                     }
                                     /* Tail recur on the value */
                                     goto recur;

src/core/string.c

@@ -336,6 +336,25 @@ void dst_description_b(DstBuffer *buffer, Dst x) {
     }
 }
 
+void dst_to_string_b(DstBuffer *buffer, Dst x) {
+    switch (dst_type(x)) {
+        default:
+            dst_description_b(buffer, x);
+            break;
+        case DST_BUFFER:
+            dst_buffer_push_bytes(buffer, 
+                    dst_unwrap_buffer(x)->data,
+                    dst_unwrap_buffer(x)->count);
+            break;
+        case DST_STRING:
+        case DST_SYMBOL:
+            dst_buffer_push_bytes(buffer, 
+                    dst_unwrap_string(x),
+                    dst_string_length(dst_unwrap_string(x)));
+            break;
+    }
+}
+
 const uint8_t *dst_description(Dst x) {
     switch (dst_type(x)) {
     case DST_NIL:
@@ -452,6 +471,10 @@ const uint8_t *dst_formatc(const char *format, ...) {
                         break;
                     }
                     case 'V': 
+                    {
+                        dst_to_string_b(bufp, va_arg(args, Dst));
+                        break;
+                    }
                     case 'v': 
                     {
                         dst_description_b(bufp, va_arg(args, Dst));