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Handle context function arguments in overloading resolution #16511

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merged 1 commit into from
Dec 15, 2022
Merged

Handle context function arguments in overloading resolution #16511

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5 changes: 4 additions & 1 deletion compiler/src/dotty/tools/dotc/ast/Desugar.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1464,7 +1464,10 @@ object desugar {
val param = makeSyntheticParameter(
tpt =
if params.exists(_.tpt.isEmpty) then TypeTree()
else Tuple(params.map(_.tpt)))
else Tuple(params.map(_.tpt)),
flags =
if params.nonEmpty && params.head.mods.is(Given) then SyntheticTermParam | Given
else SyntheticTermParam)
def selector(n: Int) =
if (isGenericTuple) Apply(Select(refOfDef(param), nme.apply), Literal(Constant(n)))
else Select(refOfDef(param), nme.selectorName(n))
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6 changes: 4 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/Applications.scala
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Expand Up @@ -1923,7 +1923,9 @@ trait Applications extends Compatibility {
/** The shape of given tree as a type; cannot handle named arguments. */
def typeShape(tree: untpd.Tree): Type = tree match {
case untpd.Function(args, body) =>
defn.FunctionOf(args map Function.const(defn.AnyType), typeShape(body))
defn.FunctionOf(
args.map(Function.const(defn.AnyType)), typeShape(body),
isContextual = untpd.isContextualClosure(tree))
case Match(EmptyTree, _) =>
defn.PartialFunctionClass.typeRef.appliedTo(defn.AnyType :: defn.NothingType :: Nil)
case _ =>
Expand Down Expand Up @@ -2232,7 +2234,7 @@ trait Applications extends Compatibility {
false
val commonFormal =
if (isPartial) defn.PartialFunctionOf(commonParamTypes.head, WildcardType)
else defn.FunctionOf(commonParamTypes, WildcardType)
else defn.FunctionOf(commonParamTypes, WildcardType, isContextual = untpd.isContextualClosure(arg))
overload.println(i"pretype arg $arg with expected type $commonFormal")
if (commonParamTypes.forall(isFullyDefined(_, ForceDegree.flipBottom)))
withMode(Mode.ImplicitsEnabled) {
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14 changes: 14 additions & 0 deletions tests/pos/i16506.scala
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@@ -0,0 +1,14 @@
import scala.annotation.targetName

trait Ctx

def foo(f: Ctx => Int) = ???

@targetName("fooContextual")
def foo(f: Ctx ?=> Int) = ???

def bar1 = foo(ctx => 123)
def bar2 = foo((ctx: Ctx) => 123)
def bar3 = foo(ctx ?=> 123)
def bar4 = foo((ctx: Ctx) ?=> 123)
// def bar5 = foo(123) does not work
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What about

def f1: Ctx => Int = ???
def f2: Ctx ?=> Int = ???

def bar6 = foo(f1)
def bar7 = foo(f2)

?
Unfortunately bar7 doesn't compile:

19 |def bar7 = foo(f2)
   |               ^^
   |               Found:    (Ctx) ?=> Int
   |               Required: Ctx => <?>

Isn't this a separate case from bar5 as f2 is already known to be a context function?

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Unfortunately, no. If we expanded bar7 it would look like this:

foo(ctx ?=> f2(using ctx)

So when we see f2 we immediately apply it to a Context argument which is missing, so compilation fails. That's baked in, and I think it will be impossible to change. We exploit this uniformity in our compilation scheme for context functions to make them more efficient.