Debugging Scala Implicits in IntelliJ

This document outlines several complementary approaches for statically analysing Scala implicits in IntelliJ.

JetBrains provides a document explaining the first two steps, but does not include the clarification around analysing enriched objects.

Note: These shortcuts are for OSX.

Viewing implicit conversions

1. Highlight the implicitly converted object.

   Important: When investigating an enriched object, you MUST highlight the object only, NOT the injected method. This is because the object is what's being converted; selecting the method will resolve implicit conversions on the object returned by that method.

2. CTRL + Q

Viewing actual implicit parameters

1. Highlight the method call-site.

2. CMD + SHIFT + P

See Viewing code without implicits if you receive 'Parameter not found'

Viewing actual implicit parameters on implicit conversions

The following requires temporary code modification:

1. Perform steps in Viewing implicit conversions.

2. Highlight appropriate implicit conversion function.

3. ALT + ENTER (and then ENTER to select 'Make explicit').

4. Perform steps in Viewing actual implicit parameters.

Viewing code without implicits

This is the last resort: it displays the 'unravelled' Scala code, which is useful if you don't have IntelliJ or IntelliJ is unable to resolve implicit parameters:

1. Run from the command line:

   sbt "set scalacOptions in Compile += \"-Xprint:typer\"" "compile"
   

2. Ignore the initial output.

3. 'Touch' the file you are interested in.

4. Re-run step 1.