Allow multiple spreads in function arguments #23855
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odersky
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| then addArg(typedArg(arg, formal), formal) | ||
| else addArg(typedArg(arg, elemFormal), elemFormal) | ||
| else | ||
| val typedArgs = harmonic(harmonizeArgs, elemFormal): |
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AFAICT, there is no equivalent code in the code path with multiSpreads. I understand it may be tricky, but it's at least worth calling out at the spec/SIP level. IIUC It means we get:
def foo[A](xs: A*): List[A] = xs.toList
foo(5, 5.6) // List[Double]
val doubles = List(5.6)
foo(5, doubles*) // List[AnyVal]Basically having any spread in a vararg argument disables harmonization entirely.
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@sjrd I got harmonization working for spreads and also implemented the other review suggestions |
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Nice!
I'm not sure what happens if we provide an Array[S] where S <: T. For example in Scala 3.7.3 we can do:
scala> def foo(x: CharSequence*): String = x.mkString
def foo(x: CharSequence*): String
scala> val strings: Array[String] = Array("foo", "bar")
val strings: Array[String] = Array(foo, bar)
scala> foo(strings*)
val res0: String = foobarWhat is then the desugaring of
scala> foo(("oof": CharSequence), strings*)It seems we can't call addArray(strings), because it requires an Array[CharSequence] and strings is an Array[String].
Good question! In fact it runs fine, but fails -Ycheck. To fix this, I changed the generated code to add a cast if needed. The example foo(("oof": CharSequence), strings*)now compiles to foo(
scala.runtime.VarArgsBuilder.ofRef[CharSequence](1 + strings.length)
.add("oof":CharSequence)
.addArray(strings.$asInstanceOf[Array[CharSequence]]).result()*
) |
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Ah yes, that works. |
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@sjrd Do you have more comments, or can we merge this? |
tests/run/i11419.scala
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| object Test { | ||
| def main(args: Array[String]): Unit = { | ||
| val arr: Array[String] = Array("foo") | ||
| val lst = List("x", arr*) // error |
We need to access them twice because we first need to take their length, then append them to the buffer. If a spread might have side effects, lift all side-effecting arguments out in the order of occurrence.
odersky
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Implements SIP 70. Currently, only
Seqs andArrays can be unpacked whereas the SIP also specifiesOptionunpacking.