There are some function calls where the return value should not be ignored (like some, indexOf, concat, map, etc.) or the function call doesn't make sense. Would be nice to cover this with the no-unused-expressions lint. I did test the snippets below on current master, they both don't fail.

functionfoo(arr){if(arr){arr.some(el=='myval');// should be: return arr.some(el == 'myval');}returnundefined;}

functionfoo(arr){varmerged=arr.reduce(function(a,b){a.concat(b);// should be: return a.concat(b);});}