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Handle FlexibleTypes in asContextFunctionType #23865

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Merged
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Sep 3, 2025
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Handle FlexibleTypes in asContextFunctionType #23865

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2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/core/Definitions.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1996,6 +1996,8 @@ class Definitions {
asContextFunctionType(TypeComparer.bounds(tp1).hiBound)
case tp1 @ PolyFunctionOf(mt: MethodType) if mt.isContextualMethod =>
tp1
case tp1: FlexibleType =>
asContextFunctionType(tp1.underlying)
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Maybe I'm missing something here so I do have a question: Why do we drop the information that this was a Flexible Type (FT) instead of wrapping it over FT?

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For the purpose here, we only want to extract the information of a context function, so it's ok to widen a flexible type. I would prefer to strip any OrNull/flexible type at the beginning of this function.

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So do you mean changing

    tp.stripTypeVar.dealias match

to

    tp.stripTypeVar.dealias.stripNull match

at the beginning (instead of adding this case)?

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Yes, maybe before stripTypeVar

case tp1 =>
if tp1.typeSymbol.name.isContextFunction && isFunctionNType(tp1) then tp1
else NoType
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14 changes: 13 additions & 1 deletion tests/explicit-nulls/flexible-unpickle/Flexible_2.scala
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@@ -1,7 +1,8 @@
import unsafeNulls.Foo.*
import unsafeNulls.Unsafe_1
import unsafeNulls.{A, B, C, F, G, H, I, J, L, M}
import unsafeNulls.{A, B, C, F, G, H, I, J, L, M, S, T, U, expects}
import scala.reflect.Selectable.reflectiveSelectable
import scala.quoted.*

class Inherit_1 extends Unsafe_1 {
override def foo(s: String): String = s
Expand Down Expand Up @@ -34,6 +35,8 @@ case class cc()
class K(val b: String) extends J(b) {
}

def typeNameMacro[A: Type](using Quotes) = Expr(Type.show[A])

@main
def Flexible_2() =
val s2: String | Null = "foo"
Expand Down Expand Up @@ -97,3 +100,12 @@ def Flexible_2() =

val m: String = M.test(null)

// i23845
transparent inline def typeName[A]: String = ${typeNameMacro[A]}

implicit val givenT: T = ???
def alphaTypeNameMacro[A: S](using T) = U(S.show[A])
def res[A] = {
implicit val givenS: S[A] = ???
expects(alphaTypeNameMacro[A])
}
6 changes: 6 additions & 0 deletions tests/explicit-nulls/flexible-unpickle/Unsafe_1.scala
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Expand Up @@ -73,3 +73,9 @@ object M {
def test(input: => String): String = "foo " + input
}

class S[X]
object S { def show[X] = "dummyStr" }
class T
class U[Y](a: Y)
def expects(take: (T) ?=> U[String]) = ???

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