Support redefinable bindings

src/core/compile.c

@@ -239,6 +239,12 @@ JanetSlot janetc_resolve(
             case JANET_BINDING_MACRO: /* Macro should function like defs when not in calling pos */
                 ret = janetc_cslot(binding.value);
                 break;
+            case JANET_BINDING_DEF_REF:
+            case JANET_BINDING_MACRO_REF:
+                ret = janetc_cslot(binding.value);
+                ret.flags |= JANET_SLOT_REF | JANET_SLOT_NAMED | JANET_SLOTTYPE_ANY;
+                ret.flags &= ~JANET_SLOT_CONSTANT;
+                break;
             case JANET_BINDING_VAR: {
                 ret = janetc_cslot(binding.value);
                 ret.flags |= JANET_SLOT_REF | JANET_SLOT_NAMED | JANET_SLOT_MUTABLE | JANET_SLOTTYPE_ANY;
@@ -651,7 +657,7 @@ static int macroexpand1(
     }
     Janet macroval;
     JanetBindingType btype = janet_resolve(c->env, name, &macroval);
-    if (btype != JANET_BINDING_MACRO ||
+    if (!(btype == JANET_BINDING_MACRO || btype == JANET_BINDING_MACRO_REF) ||
             !janet_checktype(macroval, JANET_FUNCTION))
         return 0;
 

src/core/specials.c

@@ -331,14 +331,27 @@ static int defleaf(
         JanetTable *entry = janet_table_clone(tab);
         janet_table_put(entry, janet_ckeywordv("source-map"),
                         janet_wrap_tuple(janetc_make_sourcemap(c)));
-        JanetSlot valsym = janetc_cslot(janet_ckeywordv("value"));
-        JanetSlot tabslot = janetc_cslot(janet_wrap_table(entry));
+
+        if (!janet_checktype(janet_table_get(entry, janet_ckeywordv("redef")), JANET_NIL)) {
+            JanetBinding binding = janet_resolve_ext(c->env, sym);
+            JanetArray *ref;
+            if (janet_checktype(binding.value, JANET_ARRAY)) {
+                ref = janet_unwrap_array(binding.value);
+            } else {
+                ref = janet_array(1);
+                janet_array_push(ref, janet_wrap_nil());
+            }
+            janet_table_put(entry, janet_ckeywordv("ref"), janet_wrap_array(ref));
+            JanetSlot refslot = janetc_cslot(janet_wrap_array(ref));
+            janetc_emit_ssu(c, JOP_PUT_INDEX, refslot, s, 0, 0);
+        } else {
+            JanetSlot valsym = janetc_cslot(janet_ckeywordv("value"));
+            JanetSlot tabslot = janetc_cslot(janet_wrap_table(entry));
+            janetc_emit_sss(c, JOP_PUT, tabslot, valsym, s, 0);
+        }
 
         /* Add env entry to env */
         janet_table_put(c->env, janet_wrap_symbol(sym), janet_wrap_table(entry));
-
-        /* Put value in table when evaulated */
-        janetc_emit_sss(c, JOP_PUT, tabslot, valsym, s, 0);
     }
     return namelocal(c, sym, 0, s);
 }

src/core/util.c

@@ -627,23 +627,31 @@ JanetBinding janet_resolve_ext(JanetTable *env, const uint8_t *sym) {
         binding.deprecation = JANET_BINDING_DEP_NORMAL;
     }
 
-    if (!janet_checktype(
-                janet_table_get(entry_table, janet_ckeywordv("macro")),
-                JANET_NIL)) {
+    ref = janet_table_get(entry_table, janet_ckeywordv("ref"));
+    int is_value = !janet_checktype(ref, JANET_ARRAY);
+    int is_macro = !janet_checktype(janet_table_get(entry_table, janet_ckeywordv("macro")), JANET_NIL);
+    int is_redef = !janet_checktype(janet_table_get(entry_table, janet_ckeywordv("redef")), JANET_NIL);
+
+    if (is_redef && is_value) {
+        /* invalid, return empty binding */
+        return binding;
+    } else if (is_macro && is_redef) {
+        binding.value = ref;
+        binding.type = JANET_BINDING_MACRO_REF;
+    } else if (is_macro) {
         binding.value = janet_table_get(entry_table, janet_ckeywordv("value"));
         binding.type = JANET_BINDING_MACRO;
-        return binding;
-    }
-
-    ref = janet_table_get(entry_table, janet_ckeywordv("ref"));
-    if (janet_checktype(ref, JANET_ARRAY)) {
+    } else if (is_redef) {
+        binding.value = ref;
+        binding.type = JANET_BINDING_DEF_REF;
+    } else if (is_value) {
+        binding.value = janet_table_get(entry_table, janet_ckeywordv("value"));
+        binding.type = JANET_BINDING_DEF;
+    } else {
         binding.value = ref;
         binding.type = JANET_BINDING_VAR;
-        return binding;
     }
 
-    binding.value = janet_table_get(entry_table, janet_ckeywordv("value"));
-    binding.type = JANET_BINDING_DEF;
     return binding;
 }
 

src/include/janet.h

@@ -1779,7 +1779,9 @@ typedef enum {
     JANET_BINDING_NONE,
     JANET_BINDING_DEF,
     JANET_BINDING_VAR,
-    JANET_BINDING_MACRO
+    JANET_BINDING_MACRO,
+    JANET_BINDING_DEF_REF,
+    JANET_BINDING_MACRO_REF
 } JanetBindingType;
 
 typedef struct {

test/suite0000.janet

@@ -295,6 +295,19 @@
     (++ i))
   (assert (= i 6) "when macro"))
 
+# Redefs
+
+(def noredef 0)
+(defn noredef-inc [] (+ 1 noredef))
+(assert (= 1 (noredef-inc)) "result before redef without :redef")
+(def noredef 1)
+(assert (= 1 (noredef-inc)) "result after redef without :redef")
+(def redef :redef 0)
+(defn redef-inc [] (+ 1 redef))
+(assert (= 1 (redef-inc)) "result before redef with :redef")
+(def redef :redef 1)
+(assert (= 2 (redef-inc)) "result before redef with :redef")
+
 # Denormal tables and structs
 
 (assert (= (length {1 2 nil 3}) 1) "nil key struct literal")