Finding functions that return a specific type

Question

Perhaps this is a silly question, but is there a way to find all functions (in the standard library or GOPATH) that return a specific type?

For example there are man

Answer 1

Maybe not the best way but take a look at the search field at the top of the official golang.org website. If you search for "Writer":

http://golang.org/search?q=Writer

You get many results, grouped by categories like

• Types
• Package-level declarations
• Local declarations and uses
• and Textual occurrences

Also note that io.Writer is an interface, and we all know how Go handles interfaces: when implementing an interface, there is no declaration of intent, a type implicitly implements an interface if the methods defined by the interface are declared. This means that you won't be able to find many examples where an io.Writer is created and returned because a type might be named entirely different and still be an io.Writer.

Things get a little easier if you look for a non-interface type for example bytes.Buffer.

Also in the documentation of the declaring package of the type the Index section groups functions and methods of the package by type so you will find functions and methods of the same package that return the type you're looking for right under its entry/link in the Index section.

Also note that you can check the dependencies of packages at godoc.org. For example you can see what packages import the io package which may be a good starting point to look for further examples (this would be exhausting in case of package io because it is so general that at the moment 23410 packages import it).