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Improve overloading resolution if expected type is not FunProto #14733

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merged 1 commit into from
Mar 23, 2022
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Improve overloading resolution if expected type is not FunProto #14733

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14 changes: 10 additions & 4 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 @@ -1939,12 +1939,12 @@ trait Applications extends Compatibility {

record("resolveOverloaded.FunProto", alts.length)
val alts1 = narrowBySize(alts)
//report.log(i"narrowed by size: ${alts1.map(_.symbol.showDcl)}%, %")
overload.println(i"narrowed by size: ${alts1.map(_.symbol.showDcl)}%, %")
if isDetermined(alts1) then alts1
else
record("resolveOverloaded.narrowedBySize", alts1.length)
val alts2 = narrowByShapes(alts1)
//report.log(i"narrowed by shape: ${alts2.map(_.symbol.showDcl)}%, %")
overload.println(i"narrowed by shape: ${alts2.map(_.symbol.showDcl)}%, %")
if isDetermined(alts2) then alts2
else
record("resolveOverloaded.narrowedByShape", alts2.length)
Expand Down Expand Up @@ -1977,8 +1977,14 @@ trait Applications extends Compatibility {
* new java.io.ObjectOutputStream(f)
*/
pt match {
case SAMType(mtp) => narrowByTypes(alts, mtp.paramInfos, mtp.resultType)
case _ => compat
case SAMType(mtp) =>
narrowByTypes(alts, mtp.paramInfos, mtp.resultType)
case _ =>
// pick any alternatives that are not methods since these might be convertible
// to the expected type, or be used as extension method arguments.
val convertible = alts.filterNot(alt =>
normalize(alt, IgnoredProto(pt)).widenSingleton.isInstanceOf[MethodType])
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Is using normalize really needed here or could we do:

Suggested change
normalize(alt, IgnoredProto(pt)).widenSingleton.isInstanceOf[MethodType])
alt.widenSingleton.isInstanceOf[MethodOrPoly])

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It's needed for skipping using clauses

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I see. normalize will create fresh type variables for PolyTypes, they'll be gc'ed eventually but if we wanted to avoid creating them in the first place we could perhaps have a stripPolyAndImplicit method, or add a flag to normalize for situations where we don't keep around its result.

if convertible.length == 1 then convertible else compat
}
else compat
}
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19 changes: 19 additions & 0 deletions tests/pos/i14729.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
class Foo():
def normal: Unit = println("normal")

extension (f: Foo)
def ext: Unit = println("ext")

object Bar:
def makeFoo[A]: Foo = Foo()
def makeFoo[A](s: String): Foo = Foo()

def tests: Unit =
Bar.makeFoo[Int].ext // error

(Bar.makeFoo[Int]).ext // error

val foo = Bar.makeFoo[Int]
foo.ext // ok

Bar.makeFoo[Int].normal // ok