Investigate errors printed to stdout on test compile

[zainab-ali]

Errors are printed to stdout during test compile. The code compiles successfully and all tests pass, so these errors are not critical. It would be worth investigating which compilation step is causing this.

<console>:17: error: identifier expected but integer literal found.
  type QuantityOf[A, D, U <: Unit[D]] = Quantity[A, Term[D, U, Fraction[1, 1]] :: HNil]
                                                                        ^
<console>:18: error: ']' expected but '}' found.
}
^
<console>:119: error: identifier expected but integer literal found.
      implicit ev0: fraction.Multiply.Aux[F, Fraction[P, 1], PF],
                                                         ^
<console>:133: error: ']' expected but '}' found.
  }
  ^
<console>:148: error: identifier expected but integer literal found.
      implicit ev0: fraction.Multiply.Aux[F, Fraction[1, P], PF],
                                                      ^
<console>:162: error: ']' expected but '}' found.
  }
  ^
<console>:205: error: identifier expected but integer literal found.
      ev0: Require[FD != 1],
                         ^
<console>:228: error: ']' expected but '}' found.
  }
  ^

[lewismj]

I'm not sure if this is the same thing, but I think Spire 'fixes' this with some macros:
https://github.com/non/spire/blob/master/core/shared/src/main/scala/spire/macros/Macros.scala
I guess that would be a trade-off between some spurious test compilation messages and what looks like a hefty bit of boilerplate?

[zainab-ali]

Thanks for prompting me to look into this @lewismj !

The errors are caused by the doctest plugin. I think it isn't picking up the Typelevel Scala compiler when parsing the tests, thus printing compile errors. The tests get generated successfully anyhow, and are run with Typelevel Scala, so there are no major problems.

I'll take a deep dive into this a bit later and find out if spire's macros are indeed the solution. It might be better to see if there's a flag I could set for doctest.