better streamline

mcode.cm

@@ -291,6 +291,11 @@ var mcode = function(ast) {
       emit_3("add", _bp_dest, _bp_left, _bp_right)
       return null
     }
+    // If either operand is a known number, concat is impossible
+    if (is_known_number(_bp_ln) || is_known_number(_bp_rn)) {
+      emit_numeric_binop("add")
+      return null
+    }
     // Unknown types: emit full dispatch
     var t0 = alloc_slot()
     var t1 = alloc_slot()
@@ -1217,7 +1222,7 @@ var mcode = function(ast) {
   }
 
   // Binary expression compilation
-  var gen_binary = function(node) {
+  var gen_binary = function(node, target) {
     var kind = node.kind
     var left = node.left
     var right = node.right
@@ -1272,7 +1277,8 @@ var mcode = function(ast) {
     // Standard binary ops
     left_slot = gen_expr(left, -1)
     right_slot = gen_expr(right, -1)
-    dest = alloc_slot()
+    // Use target slot for ops without multi-type dispatch (add has text+num paths)
+    dest = (target >= 0 && kind != "+") ? target : alloc_slot()
     op = binop_map[kind]
     if (op == null) {
       op = "add"
@@ -1426,9 +1432,9 @@ var mcode = function(ast) {
       return val_slot
     }
 
-    val_slot = gen_expr(right, -1)
     left_kind = left.kind
 
+    // For local name assignments, try to write directly to the var's slot
     if (left_kind == "name") {
       name = left.name
       level = left.level
@@ -1438,17 +1444,30 @@ var mcode = function(ast) {
       if (level == 0 || level == -1) {
         slot = find_var(name)
         if (slot >= 0) {
-          emit_2("move", slot, val_slot)
-        } else if (level == -1) {
+          val_slot = gen_expr(right, slot)
+          if (val_slot != slot) {
+            emit_2("move", slot, val_slot)
+          }
+          return val_slot
+        }
+        val_slot = gen_expr(right, -1)
+        if (level == -1) {
           add_instr(["set_var", name, val_slot])
         }
-      } else if (level > 0) {
-        _lv = level - 1
-        pstate = parent_states[length(parent_states) - 1 - _lv]
-        pslot = find_var_in_saved(pstate, name)
-        emit_3("put", val_slot, pslot, level)
+      } else {
+        val_slot = gen_expr(right, -1)
+        if (level > 0) {
+          _lv = level - 1
+          pstate = parent_states[length(parent_states) - 1 - _lv]
+          pslot = find_var_in_saved(pstate, name)
+          emit_3("put", val_slot, pslot, level)
+        }
       }
-    } else if (left_kind == ".") {
+      return val_slot
+    }
+
+    val_slot = gen_expr(right, -1)
+    if (left_kind == ".") {
       obj = left.left
       prop = left.right
       obj_slot = gen_expr(obj, -1)
@@ -2045,7 +2064,7 @@ var mcode = function(ast) {
     }
 
     // Binary operators (fallback)
-    return gen_binary(expr)
+    return gen_binary(expr, target)
   }
 
   // Statement compilation