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Fix #5039: Handle null:_* as varargs parameter #6418

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Merged
merged 1 commit into from
May 6, 2019
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Fix #5039: Handle null:_* as varargs parameter #6418

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2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/typer/Applications.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -556,6 +556,8 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
args match {
case arg :: Nil if isVarArg(arg) =>
addTyped(arg, formal)
case Typed(Literal(Constant(null)), _) :: Nil =>
addTyped(args.head, formal)
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Note that I used .head because args is of type List[Arg] and

  case (arg @ Typed(Literal(Constant(null)), _)) :: Nil =>
    addTyped(arg, formal)

would fail with

[error] 560 |                addTyped(arg, formal)
[error]     |                         ^^^
[error]     |Found:    dotty.tools.dotc.ast.Trees.Typed[dotty.tools.dotc.ast.Trees.Untyped](arg)
[error]     |Required: Arg

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What about just reject the code? We are moving towards null-safety, it seems it's better to reject. /cc: @abeln

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We should not always reject it. We could pass it to a Java varargs. Not sure if someone actually uses this pattern for performance reasons.

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In Java it is legal to pass null as the actual array of the varargs https://coderanch.com/t/631441/java/Varargs-null

case _ =>
val elemFormal = formal.widenExpr.argTypesLo.head
val typedArgs =
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0 ...074d074a942f48e3e24845e7f7054b76b69.scala → ...074d074a942f48e3e24845e7f7054b76b69.scala
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8 changes: 8 additions & 0 deletions tests/pos/i5039.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
class I0 {
List(null:_*)
List[Null](null:_*)
List[Nothing](null:_*)
List(1, 2, null:_*)
List(null, null:_*)
List(???, null:_*)
}