Implicit not found in clean compilation, but found in incremental compilation

[soronpo]

This was extremely difficult to minimize, and this is as short as I could make it.
In clean compilation we get an implicit not found error, but if we comment out dfVal.as(DFBool) in DFBool.scala the code compiles successfully, and afterwords we can uncomment it and still get a successful compilation.
The compilation order is affected from very little things and there is a special order that causes the implicit not to be found. To get this order various features take place and include export, inline macro, extension methods, and opaque types.

Compiler version

3.0.3-RC1-bin-20210716-cc47c56-NIGHTLY

Minimized code

Minimized project at: https://github.com/soronpo/dottybug/tree/inc_implicit_err

DFBool.scala

opaque type DFBool <: DFType with HasToken =
  DFType with HasToken

trait HasToken

extension (dfVal: DFVal[DFBool]) def bar: Unit = dfVal.as(DFBool)

final val DFBool: DFBool = ???

DFType.scala

opaque type DFType = Int
object DFType:
  extension (dfType: Int) def asFE[T <: DFType]: T = dfType.asInstanceOf[T]

  trait TC[T]:
    type Type <: DFType
    def apply(t: T): Type
  object TC:
    given ofDFType[T <: DFType]: TC[T] with
      type Type = T
      def apply(t: T): Type = t
  end TC

export DFType.asFE

DFVal.scala

opaque type DFVal[T <: DFType] = Int

extension [T <: DFType](dfVal: DFVal[T])
  def as[A](aliasType: A)(using
      tc: DFType.TC[A],
      w1: Width[?]
  ): DFVal[tc.Type] = ???

Width.scala

import scala.quoted.*

trait Width[T]:
  type Out <: Int
object Width:
  transparent inline given [T]: Width[T] = ${ getWidthMacro[T] }
  def getWidthMacro[T](using Quotes, Type[T]): Expr[Width[T]] =
    import quotes.reflect.*
    '{
      new Width[T] {
        type Out = 1
      }
    }

Output

[error] -- Error: C:\IdeaProjects\dottybug\src\main\scala\DFBool.scala:6:65 ---------------------------------------
[error] 6 |extension (dfVal: DFVal[DFBool]) def bar: Unit = dfVal.as(DFBool)
[error]   |                                                                 ^
[error]   |              no implicit argument of type DFType.TC[DFBool] was found for parameter tc of method as.
[error]   |              I found:
[error]   |
[error]   |                  DFType.TC.ofDFType[T]
[error]   |
[error]   |              But given instance ofDFType in object TC does not match type DFType.TC[DFBool].
[error] one error found

Expectation

No error.

[griggt]

Slightly smaller:

DFBool.scala

trait HasToken

opaque type DFBool <: DFType with HasToken = DFType with HasToken

def bar(v: DFVal): Unit = v.as[DFBool]

DFType.scala

opaque type DFType = Int

object DFType:
  def foo: Unit = ???

  trait TC[T]
  object TC:
    given [T <: DFType]: TC[T] = ???

export DFType.foo

trait DFVal:
  def as[A](using tc: DFType.TC[A], w: Width): Unit = ()

Width.scala

import scala.quoted.*

trait Width
object Width:
  inline given Width = ${ getWidthMacro }
  def getWidthMacro(using Quotes): Expr[Width] = '{ new Width {} }

[soronpo]

Slightly smaller:
....

Thanks. I updated the branch with your smaller example.

[mpilquist]

Is the following another example or something different? With 3.0.1

➜  cs launch scala3-repl
scala> object Foo:
     |   opaque type Bar = Int
     |   object Bar:
     |     extension (b: Bar) def flip: Bar = -b
     |     def apply(x: Int): Bar = x
     |
// defined object Foo

scala> val a = Foo.Bar(42)
val a: Foo.Bar = 42

scala> val b = a.flip
val b: Foo.Bar = -42

scala> val c = b.flip
val c: Foo.Bar = 42

scala> val d = c.flip
1 |val d = c.flip
  |        ^^^^^^
  |value flip is not a member of Foo.Bar, but could be made available as an extension method.
  |
  |The following import might fix the problem:
  |
  |  import Foo.Bar.flip
  |

scala>

[soronpo]

Is the following another example or something different? With 3.0.1

To me it looks like a separate issue

[mpilquist]

Whoops, I meant to link to #10044