only cast null constructor args for primitives

[martijnhoekstra]

before, we tried to cast applied types to the type arguments, to capture context bounds. That fails for simple generic types that then get cast to the wrong type. However, that's all unnessecary: the only nulls we need to cast are primitives, which can't be passed as null. Anyting else doesn't need a cast at all

Pull Request Checklist

• I agree to licence my contributions under the MIT licence
• I have added copyright headers to new files
• I have added tests for any changed functionality

Fixes

Fixes #519

Purpose

Fix mocking classes with generic parameters. Before, mocking class Foo(x: Option[Int]) failed

Background Context

simplifying the casts by only doing them when needed simplifies thing significantly

References

[goshacodes]

Hi, thank you for your contribution!

Could you please add more test cases before we merge it?

1. Test-case from your PR description

class WithOption(opt: Option[Int])

class WithInt(int: Int)

class WithInt(int: String)

class WithC[C[_]](foo: C[Int])

5. This one is probably already exists

class WithC[A](foo: A)

[martijnhoekstra]

Edit: The following now works:

  class WithOption(opt: Option[String])
  class WithInt(i: Int)
  class WithString(str: String)
  class WithTC[TC[_]](foo: TC[Int])
  class WithGeneric[T](t: T)
  mock[WithOption[]
  mock[WithTC[List]]
  mock[WithGeneric[Int]]
  mock[WithGeneric[String]]

The last thing left that doesn't compile but should is

  type ID[A] = A
  mock[WithTC[ID]]

This is a progression from scalamock 5, where most of this didn't work.

Original message below:

The good:

The following are fine in this MR:

  class WithOption(opt: Option[String])
  class WithInt(i: Int)
  class WithString(str: String)

The bad: none of the following compiles:

  class WithTC[TC[_]](foo: TC[Int])
  class WithGeneric[T](t: T)
  type ID[A] = A
  mock[WithTC[List]]
  mock[WithTC[ID]]
  mock[WithGeneric[Int]]
  mock[WithGeneric[String]]

the good worse: they also don't compile without this MR.

[error] -- [E007] Type Mismatch Error: /Users/martijn.hoekstra/code/ScalaMock/jvm/src/test/scala/com.paulbutcher.test/mock/MockTestJvm.scala:52:21 
[error] 52 |        val tclist = mock[WithTC[List]]
[error]    |                     ^^^^^^^^^^^^^^^^^^
[error]    |                     Found:    TC[List]
[error]    |                     Required: List[Int]
[error]    |
[error]    | longer explanation available when compiling with `-explain`
[error] -- [E007] Type Mismatch Error: /Users/martijn.hoekstra/code/ScalaMock/jvm/src/test/scala/com.paulbutcher.test/mock/MockTestJvm.scala:53:19 
[error] 53 |        val tcid = mock[WithTC[ID]]
[error]    |                   ^^^^^^^^^^^^^^^^
[error]    |                   Found:    TC[ID]
[error]    |                   Required: ID[Int]
[error]    |
[error]    | longer explanation available when compiling with `-explain`
[error] -- [E007] Type Mismatch Error: /Users/martijn.hoekstra/code/ScalaMock/jvm/src/test/scala/com.paulbutcher.test/mock/MockTestJvm.scala:54:21 
[error] 54 |        val genInt = mock[WithGeneric[Int]]
[error]    |                     ^^^^^^^^^^^^^^^^^^^^^^
[error]    |                     Found:    T
[error]    |                     Required: Int
[error]    |
[error]    | longer explanation available when compiling with `-explain`
[error] -- [E007] Type Mismatch Error: /Users/martijn.hoekstra/code/ScalaMock/jvm/src/test/scala/com.paulbutcher.test/mock/MockTestJvm.scala:55:24 
[error] 55 |        val genString = mock[WithGeneric[String]]
[error]    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |    Found:    T
[error]    |    Required: String

I expected/hoped that #517 would fix that, which I merged in.

How would you like to move forward? I can make sure there is a clean history on rebase, and mark the failing cases with ignored tests. Would that allow us to move forward with this?

[segery]

Will the following example work?

import cats.effect.Async

class A[F[_]: Async](val b: B[F])
class B[F[_]: Async](val c: C[F])
trait C[F]

Now I'm getting an error like this.

[error]  type mismatch;
[error]  found   : aa.bb.B[F]
[error]  required: aa.bb.B[cats.effect.IO]
[error]   private val handler = mock[A[IO]]

UPD: For scala 2.13

[martijnhoekstra]

I'm trying to fix that too @segery -- things seem a bit bumpy at the moment

Edit: yes, that's fixed in this MR, but only for scala 3.

[martijnhoekstra]

Some of the new tests that pass for scala 3, fail for scala 2.12 and 2.13.

To my surprise, that doesn't seem new: scalamock 5.2.0 shows the same problem: https://scastie.scala-lang.org/aTyLV1LpQ0WEfRJU6s2x5Q

Therefore I moved the tests to a scala 3 specific suite.

That, as far as I'm concerned, makes this MR ready for review again.

[goshacodes]

Looks good. @barkhorn, merge it pls