better errors

mcode.cm

@@ -22,6 +22,12 @@ var mcode = function(ast) {
     "~!": "bitnot", "[]!": "load"
   }
 
+  var binop_sym = {
+    add: "+", subtract: "-", multiply: "*", divide: "/",
+    modulo: "%", pow: "**",
+    lt: "<", le: "<=", gt: ">", ge: ">="
+  }
+
   var compound_map = {
     "+=": "add", "-=": "subtract", "*=": "multiply", "/=": "divide",
     "%=": "modulo", "&=": "bitand", "|=": "bitor", "^=": "bitxor",
@@ -67,6 +73,7 @@ var mcode = function(ast) {
   var _bp_right = 0
   var _bp_ln = null
   var _bp_rn = null
+  var _bp_op_sym = null
 
   // State save/restore for nested function compilation
   var save_state = function() {
@@ -240,6 +247,27 @@ var mcode = function(ast) {
     emit_1("null", dest)
   }
 
+  var emit_log_error = function(msg) {
+    var log_slot = alloc_slot()
+    add_instr(["access", log_slot, {kind: "name", name: "log", make: "intrinsic"}])
+    var name_slot = alloc_slot()
+    emit_const_str(name_slot, "error")
+    var msg_slot = alloc_slot()
+    emit_const_str(msg_slot, msg)
+    var args_arr = alloc_slot()
+    add_instr(["array", args_arr, 0])
+    emit_2("push", args_arr, msg_slot)
+    var result = alloc_slot()
+    var frame_slot = alloc_slot()
+    emit_3("frame", frame_slot, log_slot, 2)
+    var null_slot = alloc_slot()
+    emit_1("null", null_slot)
+    emit_3("setarg", frame_slot, 0, null_slot)
+    emit_3("setarg", frame_slot, 1, name_slot)
+    emit_3("setarg", frame_slot, 2, args_arr)
+    emit_2("invoke", frame_slot, result)
+  }
+
   var emit_jump = function(label) {
     add_instr(["jump", label])
   }
@@ -321,6 +349,7 @@ var mcode = function(ast) {
     emit_jump(done)
 
     emit_label(err)
+    emit_log_error("cannot apply '+': operands must both be text or both be numbers")
     emit_0("disrupt")
     emit_label(done)
     return null
@@ -345,6 +374,7 @@ var mcode = function(ast) {
     emit_jump(done)
 
     emit_label(err)
+    emit_log_error("cannot apply '" + _bp_op_sym + "': operands must be numbers")
     emit_0("disrupt")
     emit_label(done)
     return null
@@ -569,6 +599,7 @@ var mcode = function(ast) {
     emit_jump(done)
 
     emit_label(err)
+    emit_log_error("cannot compare with '" + _bp_op_sym + "': operands must be same type")
     emit_0("disrupt")
     emit_label(done)
     return null
@@ -589,6 +620,7 @@ var mcode = function(ast) {
     emit_jump(done)
 
     emit_label(err)
+    emit_log_error("cannot negate: operand must be a number")
     emit_0("disrupt")
     emit_label(done)
     return null
@@ -607,6 +639,7 @@ var mcode = function(ast) {
     _bp_dest = dest
     _bp_left = left
     _bp_right = right
+    _bp_op_sym = binop_sym[op_str] || op_str
     if (op_str == "add") {
       emit_add_decomposed()
     } else if (op_str == "eq") {
@@ -760,6 +793,7 @@ var mcode = function(ast) {
 
     // Error path: non-text key on function disrupts
     emit_label(error_path)
+    emit_log_error("cannot access: key must be text")
     emit_0("disrupt")
     emit_jump(done_label)
 
@@ -1427,6 +1461,7 @@ var mcode = function(ast) {
       emit_2("push", arr_slot, val_slot)
       emit_jump(guard_done)
       emit_label(guard_err)
+      emit_log_error("cannot push: target must be an array")
       emit_0("disrupt")
       emit_label(guard_done)
       return val_slot
@@ -1785,6 +1820,7 @@ var mcode = function(ast) {
           emit_2("push", a0, a1)
           emit_jump(guard_done)
           emit_label(guard_err)
+          emit_log_error("cannot push: target must be an array")
           emit_0("disrupt")
           emit_label(guard_done)
           return a1
@@ -2156,6 +2192,7 @@ var mcode = function(ast) {
           emit_2("pop", local_slot, arr_slot)
           emit_jump(guard_done)
           emit_label(guard_err)
+          emit_log_error("cannot pop: target must be an array")
           emit_0("disrupt")
           emit_label(guard_done)
         }