From a097537a038131ea4a0afbcd7f298347b99e6bcd Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Wed, 9 Feb 2022 20:23:55 -0600
Subject: [PATCH] Fix #919 - strange quasiquote behavior.

Nested expression in the quasiquote were being compiled with the "hint"
flag passed to the expression compilation, essentially telling the
compiler to put intermediates into the final slot, possibly overwriting
other intermediate values. This fix removes that flags on any recursive
calls to quasiquote.
---
 src/core/specials.c  | 10 ++++++----
 test/suite0011.janet |  9 +++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/core/specials.c b/src/core/specials.c
index f6bc6cd0..7a55ac43 100644
--- a/src/core/specials.c
+++ b/src/core/specials.c
@@ -62,6 +62,8 @@ static JanetSlot quasiquote(JanetFopts opts, Janet x, int depth, int level) {
         return janetc_cslot(janet_wrap_nil());
     }
     JanetSlot *slots = NULL;
+    JanetFopts subopts = opts;
+    subopts.flags &= ~JANET_FOPTS_HINT;
     switch (janet_type(x)) {
         default:
             return janetc_cslot(x);
@@ -82,7 +84,7 @@ static JanetSlot quasiquote(JanetFopts opts, Janet x, int depth, int level) {
                 }
             }
             for (i = 0; i < len; i++)
-                janet_v_push(slots, quasiquote(opts, tup[i], depth - 1, level));
+                janet_v_push(slots, quasiquote(subopts, tup[i], depth - 1, level));
             return qq_slots(opts, slots, (janet_tuple_flag(tup) & JANET_TUPLE_FLAG_BRACKETCTOR)
                             ? JOP_MAKE_BRACKET_TUPLE
                             : JOP_MAKE_TUPLE);
@@ -91,7 +93,7 @@ static JanetSlot quasiquote(JanetFopts opts, Janet x, int depth, int level) {
             int32_t i;
             JanetArray *array = janet_unwrap_array(x);
             for (i = 0; i < array->count; i++)
-                janet_v_push(slots, quasiquote(opts, array->data[i], depth - 1, level));
+                janet_v_push(slots, quasiquote(subopts, array->data[i], depth - 1, level));
             return qq_slots(opts, slots, JOP_MAKE_ARRAY);
         }
         case JANET_TABLE:
@@ -100,8 +102,8 @@ static JanetSlot quasiquote(JanetFopts opts, Janet x, int depth, int level) {
             int32_t len, cap = 0;
             janet_dictionary_view(x, &kvs, &len, &cap);
             while ((kv = janet_dictionary_next(kvs, cap, kv))) {
-                JanetSlot key = quasiquote(opts, kv->key, depth - 1, level);
-                JanetSlot value =  quasiquote(opts, kv->value, depth - 1, level);
+                JanetSlot key = quasiquote(subopts, kv->key, depth - 1, level);
+                JanetSlot value =  quasiquote(subopts, kv->value, depth - 1, level);
                 key.flags &= ~JANET_SLOT_SPLICED;
                 value.flags &= ~JANET_SLOT_SPLICED;
                 janet_v_push(slots, key);
diff --git a/test/suite0011.janet b/test/suite0011.janet
index 31ad99d8..3f23aed0 100644
--- a/test/suite0011.janet
+++ b/test/suite0011.janet
@@ -39,5 +39,14 @@
 
 (assert-error "compile error" (eval-string "(+ a 5)"))
 
+# 919
+(defn test
+  []
+  (var x 1)
+  (set x ~(,x ()))
+  x)
+
+(assert (= (test) '(1 ())) "issue #919")
+
 (end-suite)