Issue Description:

DRY is great and all, but sometimes repetition and local modification is preferable for maintenance and understandability. Expanding a function definition in-place can also be a useful learning aid for understanding abstractions in unfamiliar codebases. It would be cool to have a "de-factoring" action to replace a function call with the function's expanded definition, replacing the parameters (both value and generic type parameters) with their values from the call site.