correct apply check and add apply opcode

mcode.cm

@@ -2135,6 +2135,14 @@ var mcode = function(ast) {
           emit_label(guard_done)
           return a1
         }
+        // apply(fn, arr) → direct opcode
+        if (nargs == 2 && fname == "apply") {
+          a0 = gen_expr(args_list[0], -1)
+          a1 = gen_expr(args_list[1], -1)
+          d = alloc_slot()
+          emit_3("apply", d, a0, a1)
+          return d
+        }
         // Callback intrinsics → inline mcode loops
         if (fname == "arrfor" && nargs >= 2 && nargs <= 4 && inline_arrfor) {
           a0 = gen_expr(args_list[0], -1)

source/mach.c

@@ -281,6 +281,7 @@ typedef enum MachOpcode {
   MACH_IS_UPPER,      /* R(A) = is_upper(R(B)) */
   MACH_IS_WS,         /* R(A) = is_whitespace(R(B)) */
   MACH_IS_ACTOR,      /* R(A) = is_actor(R(B)) — has actor_sym property */
+  MACH_APPLY,         /* R(A) = apply(R(B), R(C)) — call fn with args from array (ABC) */
 
   MACH_OP_COUNT
 } MachOpcode;
@@ -405,6 +406,7 @@ static const char *mach_opcode_names[MACH_OP_COUNT] = {
   [MACH_IS_UPPER] = "is_upper",
   [MACH_IS_WS] = "is_ws",
   [MACH_IS_ACTOR] = "is_actor",
+  [MACH_APPLY] = "apply",
 };
 
 /* ---- Compile-time constant pool entry ---- */
@@ -1427,6 +1429,7 @@ vm_dispatch:
       DT(MACH_IS_DIGIT), DT(MACH_IS_LETTER),
       DT(MACH_IS_LOWER), DT(MACH_IS_UPPER),
       DT(MACH_IS_WS), DT(MACH_IS_ACTOR),
+      DT(MACH_APPLY),
     };
 #pragma GCC diagnostic pop
 #undef DT
@@ -2511,6 +2514,49 @@ vm_dispatch:
       frame->slots[a] = JS_NewBool(ctx, result);
       VM_BREAK();
     }
+    VM_CASE(MACH_APPLY): {
+      /* A=dest, B=fn, C=arr_or_val */
+      JSValue fn_val = frame->slots[b];
+      JSValue arg_val = frame->slots[c];
+      if (!mist_is_function(fn_val)) {
+        frame->slots[a] = fn_val;
+        VM_BREAK();
+      }
+      JSFunction *fn = JS_VALUE_GET_FUNCTION(fn_val);
+      JSValue ret;
+      ctx->reg_current_frame = frame_ref.val;
+      ctx->current_register_pc = pc > 0 ? pc - 1 : 0;
+      ctx->vm_call_depth++;
+      if (!mist_is_array(arg_val)) {
+        /* Non-array: use as single argument */
+        if (!mach_check_call_arity(ctx, fn, 1)) {
+          ctx->vm_call_depth--;
+          goto disrupt;
+        }
+        ret = JS_CallInternal(ctx, fn_val, JS_NULL, 1, &arg_val, 0);
+      } else {
+        JSArray *arr = JS_VALUE_GET_ARRAY(arg_val);
+        int len = arr->len;
+        if (!mach_check_call_arity(ctx, fn, len)) {
+          ctx->vm_call_depth--;
+          goto disrupt;
+        }
+        if (len == 0) {
+          ret = JS_CallInternal(ctx, fn_val, JS_NULL, 0, NULL, 0);
+        } else {
+          JSValue *args = alloca(sizeof(JSValue) * len);
+          for (int i = 0; i < len; i++)
+            args[i] = arr->values[i];
+          ret = JS_CallInternal(ctx, fn_val, JS_NULL, len, args, 0);
+        }
+      }
+      ctx->vm_call_depth--;
+      frame = (JSFrameRegister *)JS_VALUE_GET_PTR(frame_ref.val);
+      ctx->reg_current_frame = JS_NULL;
+      if (JS_IsException(ret)) goto disrupt;
+      frame->slots[a] = ret;
+      VM_BREAK();
+    }
     /* Logical */
     VM_CASE(MACH_NOT): {
       int bval = JS_ToBool(ctx, frame->slots[b]);
@@ -3168,6 +3214,7 @@ static MachCode *mcode_lower_func(cJSON *fobj, const char *filename) {
     else if (strcmp(op, "is_upper") == 0)  { AB2(MACH_IS_UPPER); }
     else if (strcmp(op, "is_ws") == 0)     { AB2(MACH_IS_WS); }
     else if (strcmp(op, "is_actor") == 0)  { AB2(MACH_IS_ACTOR); }
+    else if (strcmp(op, "apply") == 0)     { ABC3(MACH_APPLY); }
     /* Logical */
     else if (strcmp(op, "not") == 0)     { AB2(MACH_NOT); }
     else if (strcmp(op, "and") == 0)     { ABC3(MACH_AND); }

source/runtime.c

@@ -9432,15 +9432,23 @@ static JSValue js_cell_fn_apply (JSContext *ctx, JSValue this_val, int argc, JSV
   if (argc < 1) return JS_NULL;
   if (!JS_IsFunction (argv[0])) return argv[0];
 
+  JSFunction *fn = JS_VALUE_GET_FUNCTION (argv[0]);
+
   if (argc < 2)
     return JS_CallInternal (ctx, argv[0], JS_NULL, 0, NULL, 0);
 
-  if (!JS_IsArray (argv[1]))
+  if (!JS_IsArray (argv[1])) {
+    if (fn->length >= 0 && 1 > fn->length)
+      return JS_RaiseDisrupt (ctx, "too many arguments for apply: expected %d, got 1", fn->length);
     return JS_CallInternal (ctx, argv[0], JS_NULL, 1, &argv[1], 0);
+  }
 
   JSArray *arr = JS_VALUE_GET_ARRAY (argv[1]);
   int len = arr->len;
 
+  if (fn->length >= 0 && len > fn->length)
+    return JS_RaiseDisrupt (ctx, "too many arguments for apply: expected %d, got %d", fn->length, len);
+
   if (len == 0)
     return JS_CallInternal (ctx, argv[0], JS_NULL, 0, NULL, 0);