Method type parameter not inferred when given a dependent type

[adamw]

Compiler version

3.0.1-RC1

Minimized code

trait X {
  type Y
}

trait E[A]

trait Test {
  val x: X
  def wrap(x: X): E[x.Y] = ???
  def run[I](i: E[I]): Unit = ???
  run(wrap(x))
}

Output

[error] -- [E007] Type Mismatch Error: /Users/adamw/projects/tapir/client/tests/src/main/scala/sttp/tapir/client/tests/ClientStreamingTests.scala:35:10
[error] 35 |  run(wrap(x))
[error]    |      ^^^^^^^
[error]    |      Found:    sttp.tapir.client.tests.E[Test.this.x.Y]
[error]    |      Required: sttp.tapir.client.tests.E[?1.Y]
[error]    |
[error]    |      where:    ?1 is an unknown value of type sttp.tapir.client.tests.X
[error] Explanation
[error] ===========
[error]
[error] I tried to show that
[error]   sttp.tapir.client.tests.E[Test.this.x.Y]
[error] conforms to
[error]   sttp.tapir.client.tests.E[?1.Y]
[error] but the comparison trace ended with `false`:
[error]
[error]   ==> sttp.tapir.client.tests.E[Test.this.x.Y]  <:  sttp.tapir.client.tests.E[?1.Y]
[error]     ==> sttp.tapir.client.tests.E[Test.this.x.Y]  <:  sttp.tapir.client.tests.E[?1.Y] (recurring)
[error]       ==> ?1.Y  <:  Test.this.x.Y
[error]         ==> ?1.Y  <:  Test.this.x.Y (recurring)
[error]           ==> ?1.Y  <:  Test.this.x.Y (recurring)
[error]             ==> (?1 : sttp.tapir.client.tests.X)  <:  (Test.this.x : sttp.tapir.client.tests.X)
[error]               ==> (?1 : sttp.tapir.client.tests.X)  <:  (Test.this.x : sttp.tapir.client.tests.X) (recurring)
[error]                 ==> sttp.tapir.client.tests.X  <:  (Test.this.x : sttp.tapir.client.tests.X) (left is approximated)
[error]                   ==> sttp.tapir.client.tests.X  <:  (Test.this.x : sttp.tapir.client.tests.X) (recurring)
[error]                   <== sttp.tapir.client.tests.X  <:  (Test.this.x : sttp.tapir.client.tests.X) (recurring) = false
[error]                 <== sttp.tapir.client.tests.X  <:  (Test.this.x : sttp.tapir.client.tests.X) (left is approximated) = false
[error]               <== (?1 : sttp.tapir.client.tests.X)  <:  (Test.this.x : sttp.tapir.client.tests.X) (recurring) = false
[error]             <== (?1 : sttp.tapir.client.tests.X)  <:  (Test.this.x : sttp.tapir.client.tests.X) = false
[error]             ==> Any  <:  Test.this.x.Y (left is approximated)
[error]               ==> Any  <:  Test.this.x.Y (recurring)
[error]               <== Any  <:  Test.this.x.Y (recurring) = false
[error]             <== Any  <:  Test.this.x.Y (left is approximated) = false
[error]           <== ?1.Y  <:  Test.this.x.Y (recurring) = false
[error]         <== ?1.Y  <:  Test.this.x.Y (recurring) = false
[error]       <== ?1.Y  <:  Test.this.x.Y = false
[error]     <== sttp.tapir.client.tests.E[Test.this.x.Y]  <:  sttp.tapir.client.tests.E[?1.Y] (recurring) = false
[error]   <== sttp.tapir.client.tests.E[Test.this.x.Y]  <:  sttp.tapir.client.tests.E[?1.Y] = false
[error]
[error] The tests were made under a constraint with:
[error]  uninstantiated variables:
[error]  constrained types: [I](i: sttp.tapir.client.tests.E[I]): Unit
[error]  bounds:
[error]      I := ?1.Y
[error]  ordering:
[error] one error found

Expectation

Compile without errors :)

The above compiles fine using 2.13.

With Scala 3, the type parameter needs to be provided explicitly:

run[x.Y](wrap(x))

[romanowski]

Assigning wrap(x) to val / def also make this snippet compile.