From 9341081a4dd414171e16210bc55c0112e8ba3134 Mon Sep 17 00:00:00 2001
From: Autumn! <autumnull@protonmail.com>
Date: Mon, 12 Sep 2022 23:05:31 +0100
Subject: [PATCH] Made peg 'not' and 'if-not' drop their captures on success

---
 src/core/peg.c       | 32 +++++++++++++++++++++++++++-----
 test/suite0014.janet | 20 ++++++++++++++++++++
 2 files changed, 47 insertions(+), 5 deletions(-)
 create mode 100644 test/suite0014.janet

diff --git a/src/core/peg.c b/src/core/peg.c
index 8bfbb348..a5af27eb 100644
--- a/src/core/peg.c
+++ b/src/core/peg.c
@@ -261,24 +261,46 @@ tail:
             goto tail;
         }
 
-        case RULE_IF:
-        case RULE_IFNOT: {
+        case RULE_IF: {
             const uint32_t *rule_a = s->bytecode + rule[1];
             const uint32_t *rule_b = s->bytecode + rule[2];
             down1(s);
             const uint8_t *result = peg_rule(s, rule_a, text);
             up1(s);
-            if (rule[0] == RULE_IF ? !result : !!result) return NULL;
+            if (!result) return NULL;
             rule = rule_b;
             goto tail;
         }
+        case RULE_IFNOT: {
+            const uint32_t *rule_a = s->bytecode + rule[1];
+            const uint32_t *rule_b = s->bytecode + rule[2];
+            down1(s);
+            CapState cs = cap_save(s);
+            const uint8_t *result = peg_rule(s, rule_a, text);
+            if (!!result) {
+                up1(s);
+                return NULL;
+            } else {
+                cap_load(s, cs);
+                up1(s);
+                rule = rule_b;
+                goto tail;
+            }
+        }
 
         case RULE_NOT: {
             const uint32_t *rule_a = s->bytecode + rule[1];
             down1(s);
+            CapState cs = cap_save(s);
             const uint8_t *result = peg_rule(s, rule_a, text);
-            up1(s);
-            return (result) ? NULL : text;
+            if (result) {
+                up1(s);
+                return NULL;
+            } else {
+                cap_load(s, cs);
+                up1(s);
+                return text;
+            }
         }
 
         case RULE_THRU:
diff --git a/test/suite0014.janet b/test/suite0014.janet
new file mode 100644
index 00000000..c4fb40fa
--- /dev/null
+++ b/test/suite0014.janet
@@ -0,0 +1,20 @@
+(import ./helper :prefix "" :exit true)
+(start-suite 14)
+
+(assert (deep=
+  (peg/match '(not (* (constant 7) "a")) "hello")
+  @[]) "peg not")
+
+(assert (deep=
+  (peg/match '(if-not (* (constant 7) "a") "hello") "hello")
+  @[]) "peg if-not")
+
+(assert (deep=
+  (peg/match '(if-not (drop (* (constant 7) "a")) "hello") "hello")
+  @[]) "peg if-not drop")
+
+(assert (deep=
+  (peg/match '(if (not (* (constant 7) "a")) "hello") "hello")
+  @[]) "peg if not")
+
+(end-suite)