1 files changed, 82 insertions, 10 deletions

diff --git a/proc.c b/proc.c
index 0877a91..7e983ca 100644
--- a/proc.c
+++ b/proc.c
@@ -102,26 +102,98 @@ NameBinding *scope_bind(Scope *scope, Str name, Node *value, LexSpan pos, Graph
 	return prev;
 }
 
-NameBinding *scope_update(NameBinding *b, Node *to, Graph *g) {
+NameBinding *scope_update(Scope *scope, NameBinding *b, Node *to, Graph *g) {
 	Node *n = b->node;
+	unsigned nestlvl = scope->nestlvl;
+	for (ScopeChangeList *l = scope->changes; l; l = l->prev) {
+		if (b->nestlvl < nestlvl) {
+			scope_changelist_update(l, b, n, to, g);
+		}
+		nestlvl--;
+	}
 	node_add(g, to, g->keepalive);
 	b->node = to;
 	node_remove(g, n, g->keepalive);
 	return b;
 }
 
-/* adds to keepalive so these aren't invalidated */
-void scope_collect(Scope *scope, Graph *g, ScopeNameList *nl, Arena *arena) {
-	for (ScopeFrame *f = scope->tail; f; f = f->prev) {
-		for (NameBinding *b = f->latest; b; b = b->prev) {
-			node_add(g, b->node, g->keepalive);
-			ZDA_PUSH(arena, nl, (ScopeName) { b->name, b->node });
+void scope_changelist_update(ScopeChangeList *l, NameBinding *b, Node *from, Node *to, Graph *g) {
+	for (unsigned i = 0; i < l->n; i++) {
+		ScopeChange *chg = XAR_GET(l, i);
+		if (chg->bind == b) {
+			node_add(g, to, g->keepalive);
+			node_remove(g, chg->to, g->keepalive);
+			chg->to = to;
+			return;
+		}
+	}
+	ScopeChange *chg = XAR_PUT(l, l->n++, l->arena);
+	node_add(g, from, g->keepalive);
+	node_add(g, to, g->keepalive);
+	chg->bind = b;
+	chg->from = from;
+	chg->to = to;
+}
+
+void scope_changelist_push(Scope *scope, ScopeChangeList *l, Arena *a) {
+	l->arena = a;
+	l->prev = scope->changes;
+	scope->changes = l;
+	scope->nestlvl++;
+}
+
+void scope_changelist_pop(Scope *scope, Graph *g) {
+	ScopeChangeList *l = scope->changes;
+	scope->changes = l->prev;
+	scope->nestlvl--;
+	for (unsigned i = 0; i < l->n; i++) {
+		ScopeChange *chg = XAR_GET(l, i);
+		scope_update(scope, chg->bind, chg->from, g);
+	}
+}
+
+#include <stdio.h>
+/* TODO: implement merge, probably will need scratch arena to build up
+ * a Xar of something like struct { NameBinding *b; Node *y, *n; }. if
+ * no match for the given bind is found in the opposite change list,
+ * it gets the "from" value found in the other.
+ **/
+typedef struct {
+	NameBinding *b;
+	Node *y, *n;
+} MergeChange;
+void scope_changelist_merge(Scope *scope, ScopeChangeList *y, ScopeChangeList *n, Node *region, Graph *graph, Arena *scratch) {
+	MergeChange *m = new_arr(scratch, MergeChange, y->n + n->n);
+	unsigned c = 0;
+	for (unsigned i = 0; i < y->n; i++) {
+		ScopeChange *chg = XAR_GET(y, i);
+		m[c].b = chg->bind;
+		m[c].y = chg->to;
+		m[c].n = chg->from;
+		c++;
+	}
+	unsigned yc = c;
+	for (unsigned i = 0; i < n->n; i++) {
+		ScopeChange *chg = XAR_GET(n, i);
+		for (unsigned j = 0; j < yc; j++) {
+			if (m[j].b == chg->bind) {
+				m[j].n = chg->to;
+				goto next;
+			}
 		}
+		m[c].b = chg->bind;
+		m[c].y = chg->from;
+		m[c].n = chg->to;
+		c++;
+next:
 	}
+	fprintf(stderr, "%u\n", c);
 }
 
-void scope_uncollect(Scope *scope, Graph *g, ScopeNameList *nl) {
-	for (int i = 0; i < nl->len; i++) {
-		node_remove(g, nl->data[i].node, g->keepalive);
+void scope_changelist_discard(ScopeChangeList *l, Graph *g) {
+	for (unsigned i = 0; i < l->n; i++) {
+		ScopeChange *chg = XAR_GET(l, i);
+		node_remove(g, chg->from, g->keepalive);
+		node_remove(g, chg->to, g->keepalive);
 	}
 }