fix inline issue

mcode.cm

@@ -882,13 +882,43 @@ var mcode = function(ast) {
   var inline_find = true
 
   // --- Helper: emit arity-dispatched callback invocation ---
-  // ctx = {fn, fn_arity, result, null_s, frame, zero, one, az, ao, prefix}
+  // ctx = {fn, fn_arity, result, null_s, frame, zero, one, az, ao, prefix,
+  //        known_arity (optional — compile-time arity of callback literal)}
   // args = [slot_for_arg1, slot_for_arg2] — data args (not this)
   // max_args = 1 or 2 — how many data args to support
   var emit_arity_call = function(ctx, args, max_args) {
-    var call_one = gen_label(ctx.prefix + "_c1")
-    var call_two = gen_label(ctx.prefix + "_c2")
-    var call_done = gen_label(ctx.prefix + "_cd")
+    var call_one = null
+    var call_two = null
+    var call_done = null
+    var ka = ctx.known_arity
+    // When callback arity is known at compile time, emit only the matching
+    // call path. This avoids dead branches where parameters are nulled,
+    // which confuse the type checker after inlining (e.g. push on null).
+    if (ka != null) {
+      if (ka >= max_args) {
+        ka = max_args
+      }
+      if (ka == 0) {
+        emit_3("frame", ctx.frame, ctx.fn, 0)
+        emit_3("setarg", ctx.frame, 0, ctx.null_s)
+        emit_2("invoke", ctx.frame, ctx.result)
+      } else if (ka == 1 || max_args < 2) {
+        emit_3("frame", ctx.frame, ctx.fn, 1)
+        emit_3("setarg", ctx.frame, 0, ctx.null_s)
+        emit_3("setarg", ctx.frame, 1, args[0])
+        emit_2("invoke", ctx.frame, ctx.result)
+      } else {
+        emit_3("frame", ctx.frame, ctx.fn, 2)
+        emit_3("setarg", ctx.frame, 0, ctx.null_s)
+        emit_3("setarg", ctx.frame, 1, args[0])
+        emit_3("setarg", ctx.frame, 2, args[1])
+        emit_2("invoke", ctx.frame, ctx.result)
+      }
+      return null
+    }
+    call_one = gen_label(ctx.prefix + "_c1")
+    call_two = gen_label(ctx.prefix + "_c2")
+    call_done = gen_label(ctx.prefix + "_cd")
     emit_3("eq", ctx.az, ctx.fn_arity, ctx.zero)
     emit_jump_cond("jump_false", ctx.az, call_one)
     emit_3("frame", ctx.frame, ctx.fn, 0)
@@ -952,7 +982,7 @@ var mcode = function(ast) {
   }
 
   // --- Helper: emit a reduce loop body ---
-  // r = {acc, i, arr, fn, len, fn_arity}; emits loop updating acc in-place.
+  // r = {acc, i, arr, fn, len, fn_arity, known_arity}; emits loop updating acc in-place.
   // Caller must emit the done_label after calling this.
   var emit_reduce_loop = function(r, forward, done_label) {
     var acc = r.acc
@@ -971,7 +1001,8 @@ var mcode = function(ast) {
     var f = alloc_slot()
     var loop_label = gen_label("reduce_loop")
     var ctx = {fn: fn_slot, fn_arity: fn_arity, result: acc, null_s: null_s,
-               frame: f, zero: zero, one: one, az: az, ao: ao, prefix: "reduce"}
+               frame: f, zero: zero, one: one, az: az, ao: ao, prefix: "reduce",
+               known_arity: r.known_arity}
     emit_2("int", one, 1)
     emit_2("int", zero, 0)
     emit_1("null", null_s)
@@ -1428,7 +1459,8 @@ var mcode = function(ast) {
     emit_2("length", fn_arity, fn_slot)
     emit_2("int", zero, 0)
     emit_2("int", one, 1)
-    r = {acc: acc, i: i, arr: arr_slot, fn: fn_slot, len: len, fn_arity: fn_arity}
+    r = {acc: acc, i: i, arr: arr_slot, fn: fn_slot, len: len, fn_arity: fn_arity,
+         known_arity: args.fn_known_arity}
     if (nargs == 2) {
       null_label = gen_label("reduce_null")
       d1 = gen_label("reduce_d1")
@@ -1877,6 +1909,8 @@ var mcode = function(ast) {
     var guard_t = 0
     var guard_err = null
     var guard_done = null
+    var cb_known = null
+    var cb_p = null
 
     if (expr == null) {
       return -1
@@ -2184,7 +2218,14 @@ var mcode = function(ast) {
           a2 = nargs >= 3 ? gen_expr(args_list[2], -1) : -1
           a3 = nargs >= 4 ? gen_expr(args_list[3], -1) : -1
           d = alloc_slot()
-          return expand_inline_reduce(d, {arr: a0, fn: a1, init: a2, rev: a3}, nargs)
+          cb_known = null
+          if (args_list[1].kind == "function") {
+            cb_p = args_list[1].list
+            if (cb_p == null) cb_p = args_list[1].parameters
+            cb_known = cb_p != null ? length(cb_p) : 0
+          }
+          return expand_inline_reduce(d, {arr: a0, fn: a1, init: a2, rev: a3,
+                                          fn_known_arity: cb_known}, nargs)
         }
         // array(arr, fn) → inline map expansion
         // Skip when first arg is a number literal (that's array(N, fn) — creation, not map)

streamline.ce

@@ -17,6 +17,7 @@ var show_ir = false
 var show_check = false
 var show_types = false
 var show_diagnose = false
+var no_inline = false
 var filename = null
 var i = 0
 var di = 0
@@ -33,6 +34,8 @@ for (i = 0; i < length(args); i++) {
     show_types = true
   } else if (args[i] == '--diagnose') {
     show_diagnose = true
+  } else if (args[i] == '--no-inline') {
+    no_inline = true
   } else if (args[i] == '--help' || args[i] == '-h') {
     log.console("Usage: cell streamline [--stats] [--ir] [--check] [--types] [--diagnose] <file>")
     $stop()
@@ -58,6 +61,11 @@ var compiled = null
 if (show_diagnose) {
   compiled = shop.mcode_file(filename)
   compiled._warn = true
+  if (no_inline) compiled._no_inline = true
+  optimized = use('streamline')(compiled)
+} else if (no_inline) {
+  compiled = shop.mcode_file(filename)
+  compiled._no_inline = true
   optimized = use('streamline')(compiled)
 } else {
   optimized = shop.compile_file(filename)
@@ -363,12 +371,12 @@ if (show_diagnose) {
     di = 0
     while (di < length(optimized._diagnostics)) {
       diag = optimized._diagnostics[di]
-      print(`${diag.file}:${text(diag.line)}:${text(diag.col)}: ${diag.severity}: ${diag.message}`)
+      log.compile(`${diag.file}:${text(diag.line)}:${text(diag.col)}: ${diag.severity}: ${diag.message}`)
       di = di + 1
     }
-    print(`\n${text(length(optimized._diagnostics))} diagnostic(s)`)
+    log.compile(`\n${text(length(optimized._diagnostics))} diagnostic(s)`)
   } else {
-    print("No diagnostics.")
+    log.compile("No diagnostics.")
   }
 }
 

streamline.cm

@@ -3213,6 +3213,9 @@ var streamline = function(ir, log) {
   }
 
   // Phase 2: Inline pass
+  if (ir._no_inline) {
+    return ir
+  }
   var changed_main = false
   var changed_fns = null
   if (ir.main != null) {

vm_suite.ce

@@ -6928,6 +6928,17 @@ run("reduce counting with predicate", function() {
   assert_eq(result, 3, "reduce count evens")
 })
 
+run("reduce building array", function() {
+  var result = reduce([1, 2, 3], function(acc, x) {
+    acc[] = x * 2
+    return acc
+  }, [])
+  assert_eq(length(result), 3, "reduce array build length")
+  assert_eq(result[0], 2, "reduce array [0]")
+  assert_eq(result[1], 4, "reduce array [1]")
+  assert_eq(result[2], 6, "reduce array [2]")
+})
+
 // ============================================================================
 // SOME - COMPLETE COVERAGE
 // ============================================================================