Question

I spent half an hour finding the answer to this question. Posting it here along with an answer, hoping it’ll save someone half an hour.

When compiling this code

"use strict";
/**
 * These are the flower and the instrument used in the code below.
 */
var flower, instrument;

the Closure Compiler gives us this warning

JSC_MULTIPLE_VAR_DEF: declaration of multiple variables with shared type information at line 6 character 0
var flower, instrument;
^

What does this vague warning mean?

Answer 1

The Closure Compiler allows you to define type information for variables, inside comments. Like so:

/**
 * The amount of beats in each minute.
 * @type {number}
 */
var bpm = 89;

Even though the comment in the example doesn’t contain any type information, the compiler complains that if such type information existed, it would only be used for the first variable (flower) and not for the second one (instrument.)