Is there a systematic way to discover which implicit defs are in scope, and which one is bound at a particular point?

Question

Often there\'s no need to pay any attention to implicit arguments in Scala, but sometimes it\'s very helpful to understand how the compiler is automatically providing them.

Answer 1

Ideally, one day IDE integration would provide this information in some way, ...

That day is today in with JetBrains' IDEA. If you run the latest EAP of IDEA version 9 (9.0.3 EA #95.289) with a recent nightly release of the Scala plug-in, this capability is present. Every value expression may be selected and a command issued that displays a pop-up showing all applicable implicit conversions with the one the compiler will select highlighted.

And since there are apparently a few out there who don't yet know it, there is a free and open-source Community Edition of IDEA and it does support the Scala plug-in.

Answer 2

1. Add the option -Xprint:typer to the scalac command line. This prints the program tree just after the typer compiler phase. This works best with a short, self contained example. You can also pass this to scalac. This is a really huge step towards self-reliance in Scala!
2. As mentioned by Randall, IntelliJ shows in-scope and the selected Implicit View with CTRL-ALT-SHIFT-I. Wait a month or two and implicit arguments are likely to have similar support.