add pre-checking

calc.js

@@ -8,6 +8,8 @@ import calc, {
 import assert from "assert";
 import chev, { Lexer } from "chevrotain";
 
+const gen = Generations.get(9);
+
 /**
  * Creates a lexer.
  *
@@ -266,7 +268,11 @@ function parseAndCalculate(line) {
     }
   }
 
-  const gen = Generations.get(8);
+  // Pre-checking before the calculator throws unreadable errors.
+  if (!gen.species.get(attacker)) throw Error(`No species ${attacker}`);
+  if (!gen.species.get(defender)) throw Error(`No species ${attacker}`);
+  if (!gen.moves.get(move)) throw Error(`No move ${move}`);
+
   return calculate(
     gen,
     new Pokemon(gen, attacker, attackerOpts),