Confusing suggested import involving inline implicit

[mpilquist]

Minimized code

import munit.FunSuite

class Example extends FunSuite {
  1.asdf
}

Output

[error] 4 |  1.asdf
[error]   |  ^^^^^^
[error]   |value asdf is not a member of Int, but could be made available as an extension method.
[error]   |
[error]   |The following import might make progress towards fixing the problem:
[error]   |
[error]   |  import munit.Clue.generate
[error]   |
[error] one error found

Expectation

Expected:

[error] 2 |  1.asdf
[error]   |  ^^^^^^
[error]   |  value asdf is not a member of Int

Dotty 0.27.0-RC1 suggests munit.Clue.generate to fix this issue. The clue method and Clue class are defined as:

inline implicit def generate[T](value: T): Clue[T] = ${ clueImpl('value) }

class Clue[+T](
    val source: String,
    val value: T,
    val valueType: String
)

[sjrd]

I've seen this problem before with another inline implicit def. I think the suggestion mechanism believes that inline defs can return anything, this potentially a more precise result that happens to be helpful in the given context. Whereas in fact blackbox inline defs cannot return a more specific type.

[nicolasstucki]

I could not reproduce it, I only get the error. @mpilquist could you write a self-contained code snipped that reproduces the issue?

[mpilquist]

@nicolasstucki I'll work on a standalone reproduction but here's an executable one in the meantime: https://scastie.scala-lang.org/bG9JkRnARomdC2pCPD5eAQ

[mpilquist]

OK this reproduces:

Clue.scala:

package foo

import scala.language.implicitConversions

class Clue[+T](val value: T)

object Clue {
  import scala.quoted._

  inline implicit def generate[T](value: T): Clue[T] = ${ clueImpl('value) }

  def clueImpl[T:Type](value: Expr[T])(using qctx: QuoteContext): Expr[Clue[T]] = '{ new Clue($value) }
}

Main.scala:

package foo

object Main {
  // If this def is removed, there's no suggestion to import Clue.generate
  def toClue[A](a: A): Clue[A] = Clue.generate(a)

  1.asdf
}

[olafurpg]

FWIW, we have been able to reproduce the same issue for regular implicit def without inline

https://github.com/scalameta/munit/blob/8558ab134313c30f94936c5a1ca5596bda4d6c67/tests/shared/src/test/scala/munit/AssertionsSuite.scala#L214

The implicit def implementation

https://github.com/scalameta/munit/blob/8558ab134313c30f94936c5a1ca5596bda4d6c67/tests/shared/src/main/scala/munit/CustomCompare.scala#L15

[nicolasstucki]

@olafurpg the original issue is already fixed. Could you check your use case with the current master to see if that one also got fixed? Otherwise, we should open another issue with that new scenario.

[tgodzik]

Looks like we have a new case that's failing:
https://github.com/alessandrocandolini/munit-clue-confusing-suggestion

[julienrf]

Can the fix be backported to 3.3.x? Who should I ask for?

[nicolasstucki]

We had to revert the commit that closed this issue to fix #19415