bug: :vars not usable with :counter in @(repeat).

This is a regression due to a March 2016 commit which
introduced the ability for :vars in an output-side @(repeat)
block to have initial values.

The bug has the effect that all arguments in @(repeat)
which are conses/lists get duplicated, which messes up
the property list structure.

* parser.y (expand_repeat_rep_args): Do not unconditionally
add reg to the output at the bottom of the loop. A few
cases above in the consp(arg) case handle that themselves, and
do not continue the loop, so control ends up at the bottom,
adding a spurious item. By removing this list_collect,
we have to introduce it to just one case which relies on it.

* tests/008/repeat.txr,
* tests/008/repeat.expected: New files.

* y.tab.c.shipped: Updated.

4 files changed, 11 insertions, 2 deletions

diff --git a/parser.y b/parser.y
index 91643693..2a42923c 100644
--- a/parser.y
+++ b/parser.y
@@ -1634,10 +1634,10 @@ static val expand_repeat_rep_args(val args)
       }
     } else if (exp_pair) {
       match_reg_var(arg);
+      ptail = list_collect(ptail, arg);
     }
 
     exp_pair = exp_pairs = nil;
-    ptail = list_collect(ptail, arg);
   }
 
   return out;
diff --git a/tests/008/repeat.expected b/tests/008/repeat.expected
new file mode 100644
index 00000000..495d096a
--- /dev/null
+++ b/tests/008/repeat.expected
@@ -0,0 +1,3 @@
+1 3 a
+2 3 b
+3 3 c
diff --git a/tests/008/repeat.txr b/tests/008/repeat.txr
new file mode 100644
index 00000000..dba54831
--- /dev/null
+++ b/tests/008/repeat.txr
@@ -0,0 +1,6 @@
+@(bind a ("a" "b" "c"))
+@(output)
+@(repeat :counter (i 1) :vars ((x (len a))))
+@i @x @a
+@(end)
+@(end)
diff --git a/y.tab.c.shipped b/y.tab.c.shipped
index 31da32e7..f1377d67 100644
--- a/y.tab.c.shipped
+++ b/y.tab.c.shipped
@@ -7351,10 +7351,10 @@ static val expand_repeat_rep_args(val args)
       }
     } else if (exp_pair) {
       match_reg_var(arg);
+      ptail = list_collect(ptail, arg);
     }
 
     exp_pair = exp_pairs = nil;
-    ptail = list_collect(ptail, arg);
   }
 
   return out;