Using kotlin mutable collections for typenames

[AlecKazakova]

If I do

MutableList::class.asTypeName()

the generated code uses kotlin.collections.List

I have worked around with ClassName("kotlin.collections", "MutableList")

[swankjesse]

This might be a problem with Kotlin itself.

assertThat(MutableList::class.qualifiedName).isEqualTo("kotlin.collections.MutableList")

org.junit.ComparisonFailure: 
Expected :kotlin.collections.MutableList
Actual   :kotlin.collections.List

[swankjesse]

... looks like MutableList is completely erased at compile-time.

assertThat(MutableList::class).isEqualTo(List::class)

[AlecKazakova]

should this be something kotlinpoet addresses then? List::class.asMutableTypeName() or better to just leave it as the manual ClassName usage

given your findings its probably impossible to have something thats safe at compile time

[swankjesse]

asMutableTypeName() is an interesting idea!

[afollestad]

Yeah something like...

fun KClass<*>.asMutableTypeName(): ClassName {
  return when (this) {
    List::class -> MUTABLE_LIST
    Map::class -> MUTABLE_MAP
    Set::class -> MUTABLE_SET
    else -> asTypeName()
  }
}

...is handy

[Egorand]

@afollestad btw we've introduced a large number of constants for frequently used ClassNames:

fun KClass<*>.asMutableTypeName(): ClassName {
  return when (this) {
    List::class -> MUTABLE_LIST
    Map::class -> MUTABLE_MAP
    Set::class -> MUTABLE_SET
    else -> asTypeName()
  }
}

[ZacSweers]

This, annoyingly, isn't covered by the new typeOf() API either :/

@Test
fun typeNameOf_mutable() {
  val type = typeNameOf<MutableList<String>>()
  assertThat(type.toString()).isEqualTo("kotlin.collections.MutableList<kotlin.String>")
}

yields

expected: kotlin.collections.MutableList<kotlin.String>
but was : kotlin.collections.List<kotlin.String>

[ZacSweers]

This is filed now https://youtrack.jetbrains.com/issue/KT-35877

[seelikes]

facing the same problem, no way to create a property with MutableList type, please help

[Dutch-0]

facing the same problem, no way to create a property with MutableList type, please help

Did you actually read the issue?

I have worked around with ClassName("kotlin.collections", "MutableList")