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Convert SAM result types to function types #17740

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Jun 18, 2023
Merged

Convert SAM result types to function types #17740

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8812638
Convert SAM result types to function types
dwijnand May 31, 2023
9880cea
Avoid SAM with param-dependent result crashing
dwijnand Jun 5, 2023
f641a87
Fix guarding & converting SAM result type to a function type
dwijnand Jun 6, 2023
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5 changes: 4 additions & 1 deletion compiler/src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1335,7 +1335,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
case RefinedType(parent, nme.apply, mt @ MethodTpe(_, formals, restpe))
if (defn.isNonRefinedFunction(parent) || defn.isErasedFunctionType(parent)) && formals.length == defaultArity =>
(formals, untpd.DependentTypeTree(syms => restpe.substParams(mt, syms.map(_.termRef))))
case SAMType(mt @ MethodTpe(_, formals, restpe)) =>
case pt1 @ SAMType(mt @ MethodTpe(_, formals, methResType)) =>
val restpe = methResType match
case mt: MethodType if !mt.isParamDependent => mt.toFunctionType(isJava = pt1.classSymbol.is(JavaDefined))
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What happens if mt is ParamDependent? Can we still get a crash then?

Maybe we should in that case fall back to the default composition with wildcard types?

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I tried and I think if you make it param dependent it doesn't qualify as a SAM type? I guess it'll be good to have a case in, just to prove it doesn't crash the compiler - and that way you can review that I've written the test case correctly.

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I tried and I think if you make it param dependent it doesn't qualify as a SAM type?

I doubt that. Types with ParamDependent method types cannot be SAM types. But I don't see that ParamDependent result types are excluded.

case tp => tp
(formals,
if (mt.isResultDependent)
untpd.DependentTypeTree(syms => restpe.substParams(mt, syms.map(_.termRef)))
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9 changes: 9 additions & 0 deletions tests/pos/i17183.scala
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@@ -0,0 +1,9 @@
trait Dependency

trait MyFunc {
def apply(a: Int, b: String)(using Dependency): String
}

case class Context(f: MyFunc)

def test = Context(f = (_, _) => ???)