Julia is capable of delivering very good performance (in many cases on par with optimized C), but some of the concepts that enable this performance are not obvious for programmers new to the language. Base contains some tools to inspect code for performance problems, but those are not very beginner friendly and hard to integrate into an IDE. Displaying performance lint warnings directly in the source code will make it much easier to spot and correct performance problems for new and seasoned programmers alike. In some cases it might even be possible to offer automated fixes for common performance issues (e.g. changing the type of a local variable or using non-const globals).