fix: invalid capture cache

If a capture was specified in a different branch of an if statement,
then we would incorrectly think that we had already loaded it in the
parent environment.

examples/regression/regression1.tl

@@ -0,0 +1,5 @@
+(let
+    ((b: num 41))
+    ((if #f
+        (lambda () (let ((k: num b)) k))
+        (lambda () b))))

examples/regression/regression2.tl

@@ -0,0 +1,2 @@
+ (let ((a: (-> (-> num)) (lambda () (lambda () (- 16 ((lambda () 5))))))(b: (-> bool) (lambda () #f))(c: num 156)(d: List<bool> (list: bool #f (= (if #t (let ((a: num (/ 24 (* (- (+ 40 (if #f 89 316)) 95) (+ (* 470 194) (let ((a: num (- 46 293))(b: num (/ 374 217))) a)))))(b: num 15)) (((let ((c: num b)(d: num (+ (/ 56 122) (* 7 60)))) (lambda () (lambda () 6)))))) (+ 32 (- 398 24))) 62)))) (let ((e: Ref num (ref: num 19))(f: List<num> (list: num 169))(g: (-> num) (lambda () (if #t ((lambda () (if #t (let ((e: num (if #f 143 (/ 104 205)))(f: num 235)(g: num (let ((e: num ((lambda () 189)))(f: num ((lambda () 8)))(g: num 152)(h: num 21)) (let ((i: num 98)(j: num 92)) 326)))) 122) (* 90 (/ 11 (let ((e: num 26)(f: num 155)(g: num 11)(h: num 66)(i: num 124)) 20)))))) (* 384 102))))(h: num (/ (if (< 56 (- 75 58)) (if ((lambda () (= (let ((e: num c)(f: num 108)(g: num (* 141 65))(h: num 2)) 65) (- c 13)))) c 31) 38) ((lambda () (+ (if ((lambda () (= 49 75))) 208 38) (- (if (> 58 110) 14 c) 335))))))) 20))
+

examples/test.zig

@@ -195,6 +195,11 @@ test "identifiers" {
     try expectResult(@embedFile("identifiers.dl"), .definelang, "41.0");
 }
 
+test "regression" {
+    try expectResult(@embedFile("regression/regression1.tl"), .typelang, "41.0");
+    try expectResult(@embedFile("regression/regression2.tl"), .typelang, "20.0");
+}
+
 fn fuzzCodegen(initial_source: []const u8) !void {
     const source = std.testing.allocator.dupeZ(u8, initial_source) catch return;
     defer std.testing.allocator.free(source);

src/CodeGen.zig

@@ -339,11 +339,11 @@ fn genIdentifier(cg: *CodeGen, exe: *Executable, identifier: []const u8, comptim
                 });
                 if (!gop.found_existing) {
                     gop.value_ptr.* = try cg.allocCapture();
-                    try parent.emit(.move_capture, .{
-                        .local = local,
-                        .capture = @intCast(gop.value_ptr.*),
-                    }, null);
                 }
+                try parent.emit(.move_capture, .{
+                    .local = local,
+                    .capture = @intCast(gop.value_ptr.*),
+                }, null);
                 try exe.emit(.load_capture, @intCast(exe.captures.items.len), null);
                 try exe.captures.append(cg.gpa, gop.value_ptr.*);
                 if (is_typed) return parent.local_types.items[local];

src/Executable.zig

@@ -54,6 +54,10 @@ pub const Instruction = union(enum(u8)) {
         local: u16,
         capture: u16,
     },
+    move_capture_u8: struct {
+        local: u8,
+        capture: u8,
+    },
     load_local: u16,
     load_local_u8: u8,
     load_define: u16,
@@ -105,6 +109,8 @@ pub fn emit(
         return exe.emit(.move_local_u8, @intCast(payload), source_hint);
     } else if (tag == .move_define and payload <= std.math.maxInt(u8)) {
         return exe.emit(.move_define_u8, @intCast(payload), source_hint);
+    } else if (tag == .move_capture and payload.local <= std.math.maxInt(u8) and payload.capture <= std.math.maxInt(u8)) {
+        return exe.emit(.move_capture_u8, .{ .local = @intCast(payload.local), .capture = @intCast(payload.capture) }, source_hint);
     } else if (tag == .push_list and payload <= std.math.maxInt(u8)) {
         return exe.emit(.push_list_u8, @intCast(payload), source_hint);
     } else if (tag == .call and payload <= std.math.maxInt(u8)) {

src/Vm.zig

@@ -397,7 +397,7 @@ fn executeInner(vm: *Vm, cur: *StackInfo, program: *const Executable) ![]Value {
                 .move_define, .move_define_u8 => {
                     vm.stack.items[payload] = vm.stack.pop();
                 },
-                .move_capture => {
+                .move_capture, .move_capture_u8 => {
                     vm.stack.items[vm.captures_start + payload.capture] = vm.stack.items[cur.stack_start + payload.local];
                 },
                 .jump => {