Add Input.asNumberOrNaN

Might be used later

src/compiler/jsgen.js

@@ -42,6 +42,7 @@ const generatorNameVariablePool = new VariablePool('gen');
 /**
  * @typedef Input
  * @property {() => string} asNumber
+ * @property {() => string} asNumberOrNaN
  * @property {() => string} asString
  * @property {() => string} asBoolean
  * @property {() => string} asUnknown
@@ -66,6 +67,11 @@ class TypedInput {
         return `(+${this.source} || 0)`;
     }
 
+    asNumberOrNaN () {
+        if (this.type === TYPE_NUMBER || this.type === TYPE_NUMBER_NAN) return this.source;
+        return `(+${this.source})`;
+    }
+
     asString () {
         if (this.type === TYPE_STRING) return this.source;
         return `("" + ${this.source})`;
@@ -106,6 +112,10 @@ class ConstantInput {
         return '0';
     }
 
+    asNumberOrNaN () {
+        return this.asNumber();
+    }
+
     asString () {
         return `"${sanitize('' + this.constantValue)}"`;
     }