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WojciechMazurWojciechMazur
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Backport "Check user defined PolyFunction refinements " to LTS (#20700)
Backports #18457 to the LTS branch. PR submitted by the release tooling. [skip ci]
2 parents 1a43a43 + 54f5421 commit 3b94fb2

19 files changed

+126
-1
lines changed

‎compiler/src/dotty/tools/dotc/core/Definitions.scala

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@@ -1157,6 +1157,17 @@ class Definitions {
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if tpe.refinedName == nme.apply && tpe.parent.derivesFrom(defn.PolyFunctionClass) =>
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Some(mt)
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case _ => None
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def isValidPolyFunctionInfo(info: Type)(using Context): Boolean =
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def isValidMethodType(info: Type) = info match
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case info: MethodType =>
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!info.resType.isInstanceOf[MethodOrPoly] && // Has only one parameter list
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!info.isVarArgsMethod &&
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!info.isMethodWithByNameArgs // No by-name parameters
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case _ => false
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info match
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case info: PolyType => isValidMethodType(info.resType)
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case _ => isValidMethodType(info)
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}
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object ErasedFunctionOf {

‎compiler/src/dotty/tools/dotc/core/Types.scala

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@@ -419,6 +419,12 @@ object Types {
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case _ => false
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}
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/** Is this the type of a method that has a by-name parameters? */
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def isMethodWithByNameArgs(using Context): Boolean = stripPoly match {
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case mt: MethodType => mt.paramInfos.exists(_.isInstanceOf[ExprType])
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case _ => false
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}
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/** Is this the type of a method with a leading empty parameter list?
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*/
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def isNullaryMethod(using Context): Boolean = stripPoly match {

‎compiler/src/dotty/tools/dotc/transform/PostTyper.scala

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@@ -375,13 +375,15 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
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case tree: ValDef =>
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registerIfHasMacroAnnotations(tree)
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checkErasedDef(tree)
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Checking.checkPolyFunctionType(tree.tpt)
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val tree1 = cpy.ValDef(tree)(rhs = normalizeErasedRhs(tree.rhs, tree.symbol))
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if tree1.removeAttachment(desugar.UntupledParam).isDefined then
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checkStableSelection(tree.rhs)
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processValOrDefDef(super.transform(tree1))
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case tree: DefDef =>
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registerIfHasMacroAnnotations(tree)
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checkErasedDef(tree)
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Checking.checkPolyFunctionType(tree.tpt)
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annotateContextResults(tree)
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val tree1 = cpy.DefDef(tree)(rhs = normalizeErasedRhs(tree.rhs, tree.symbol))
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processValOrDefDef(superAcc.wrapDefDef(tree1)(super.transform(tree1).asInstanceOf[DefDef]))
@@ -483,6 +485,9 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
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)
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case Block(_, Closure(_, _, tpt)) if ExpandSAMs.needsWrapperClass(tpt.tpe) =>
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superAcc.withInvalidCurrentClass(super.transform(tree))
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case tree: RefinedTypeTree =>
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Checking.checkPolyFunctionType(tree)
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super.transform(tree)
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case _: Quote =>
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ctx.compilationUnit.needsStaging = true
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super.transform(tree)

‎compiler/src/dotty/tools/dotc/typer/Checking.scala

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@@ -804,6 +804,31 @@ object Checking {
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else Feature.checkExperimentalFeature("features", imp.srcPos)
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case _ =>
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end checkExperimentalImports
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/** Checks that PolyFunction only have valid refinements.
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*
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* It only supports `apply` methods with one parameter list and optional type arguments.
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*/
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def checkPolyFunctionType(tree: Tree)(using Context): Unit = new TreeTraverser {
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def traverse(tree: Tree)(using Context): Unit = tree match
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case tree: RefinedTypeTree if tree.tpe.derivesFrom(defn.PolyFunctionClass) =>
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if tree.refinements.isEmpty then
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reportNoRefinements(tree.srcPos)
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tree.refinements.foreach {
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case refinement: DefDef if refinement.name != nme.apply =>
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report.error("PolyFunction only supports apply method refinements", refinement.srcPos)
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case refinement: DefDef if !defn.PolyFunctionOf.isValidPolyFunctionInfo(refinement.tpe.widen) =>
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report.error("Implementation restriction: PolyFunction apply must have exactly one parameter list and optionally type arguments. No by-name nor varags are allowed.", refinement.srcPos)
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case _ =>
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}
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case _: RefTree if tree.symbol == defn.PolyFunctionClass =>
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reportNoRefinements(tree.srcPos)
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case _ =>
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traverseChildren(tree)
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def reportNoRefinements(pos: SrcPos) =
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report.error("PolyFunction subtypes must refine the apply method", pos)
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}.traverse(tree)
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}
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trait Checking {

‎compiler/src/dotty/tools/dotc/typer/Nullables.scala

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@@ -507,7 +507,7 @@ object Nullables:
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def postProcessByNameArgs(fn: TermRef, app: Tree)(using Context): Tree =
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fn.widen match
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case mt: MethodType
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if mt.paramInfos.exists(_.isInstanceOf[ExprType]) && !fn.symbol.is(Inline) =>
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if mt.isMethodWithByNameArgs && !fn.symbol.is(Inline) =>
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app match
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case Apply(fn, args) =>
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object dropNotNull extends TreeMap:

‎tests/neg/i18302b.check

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@@ -0,0 +1,4 @@
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-- Error: tests/neg/i18302b.scala:3:32 ---------------------------------------------------------------------------------
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3 |def polyFun: PolyFunction { def apply(x: Int)(y: Int): Int } = // error
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|Implementation restriction: PolyFunction apply must have exactly one parameter list and optionally type arguments. No by-name nor varags are allowed.

‎tests/neg/i18302b.scala

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def test = polyFun(1)(2)
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def polyFun: PolyFunction { def apply(x: Int)(y: Int): Int } = // error
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new PolyFunction:
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def apply(x: Int)(y: Int): Int = x + y

‎tests/neg/i18302c.check

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-- Error: tests/neg/i18302c.scala:4:32 ---------------------------------------------------------------------------------
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4 |def polyFun: PolyFunction { def foo(x: Int): Int } = // error
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| ^^^^^^^^^^^^^^^^^^^^
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| PolyFunction only supports apply method refinements

‎tests/neg/i18302c.scala

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import scala.reflect.Selectable.reflectiveSelectable
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def test = polyFun.foo(1)
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def polyFun: PolyFunction { def foo(x: Int): Int } = // error
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new PolyFunction { def foo(x: Int): Int = x + 1 }

‎tests/neg/i18302d.check

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-- Error: tests/neg/i18302d.scala:1:32 ---------------------------------------------------------------------------------
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1 |def polyFun: PolyFunction { def apply: Int } = // error
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| ^^^^^^^^^^^^^^
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|Implementation restriction: PolyFunction apply must have exactly one parameter list and optionally type arguments. No by-name nor varags are allowed.

‎tests/neg/i18302d.scala

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@@ -0,0 +1,2 @@
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def polyFun: PolyFunction { def apply: Int } = // error
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new PolyFunction { def apply: Int = 1 }

‎tests/neg/i18302e.check

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-- Error: tests/neg/i18302e.scala:1:13 ---------------------------------------------------------------------------------
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1 |def polyFun: PolyFunction { } = // error
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| ^^^^^^^^^^^^^^^^^
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| PolyFunction subtypes must refine the apply method
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-- Error: tests/neg/i18302e.scala:4:15 ---------------------------------------------------------------------------------
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4 |def polyFun(f: PolyFunction { }) = () // error
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| ^^^^^^^^^^^^^^^^^
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| PolyFunction subtypes must refine the apply method

‎tests/neg/i18302e.scala

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def polyFun: PolyFunction { } = // error
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new PolyFunction { }
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def polyFun(f: PolyFunction { }) = () // error

‎tests/neg/i18302f.check

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-- Error: tests/neg/i18302f.scala:1:13 ---------------------------------------------------------------------------------
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1 |def polyFun: PolyFunction = // error
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| ^^^^^^^^^^^^
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| PolyFunction subtypes must refine the apply method
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-- Error: tests/neg/i18302f.scala:4:16 ---------------------------------------------------------------------------------
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4 |def polyFun2(a: PolyFunction) = () // error
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| ^^^^^^^^^^^^
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| PolyFunction subtypes must refine the apply method
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-- Error: tests/neg/i18302f.scala:6:14 ---------------------------------------------------------------------------------
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6 |val polyFun3: PolyFunction = // error
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| ^^^^^^^^^^^^
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| PolyFunction subtypes must refine the apply method

‎tests/neg/i18302f.scala

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@@ -0,0 +1,7 @@
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def polyFun: PolyFunction = // error
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new PolyFunction { }
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def polyFun2(a: PolyFunction) = () // error
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val polyFun3: PolyFunction = // error
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new PolyFunction { }

‎tests/neg/i18302i.scala

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def polyFun1: Option[PolyFunction] = ??? // error
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def polyFun2: PolyFunction & Any = ??? // error
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def polyFun3: Any & PolyFunction = ??? // error
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def polyFun4: PolyFunction | Any = ??? // error
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def polyFun5: Any | PolyFunction = ??? // error
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def polyFun6(a: Any | PolyFunction) = ??? // error

‎tests/neg/i18302j.scala

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def polyFunByName: PolyFunction { def apply(thunk: => Int): Int } = // error
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new PolyFunction { def apply(thunk: => Int): Int = 1 }
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def polyFunVarArgs: PolyFunction { def apply(args: Int*): Int } = // error
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new PolyFunction { def apply(thunk: Int*): Int = 1 }

‎tests/neg/i8299.scala

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@@ -0,0 +1,8 @@
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package example
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object Main {
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def main(a: Array[String]): Unit = {
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val p: PolyFunction = // error: PolyFunction subtypes must refine the apply method
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[A] => (xs: List[A]) => xs.headOption
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}
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}

‎tests/pos/i18302a.scala

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def test = polyFun(1)
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def polyFun: PolyFunction { def apply(x: Int): Int } =
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new PolyFunction { def apply(x: Int): Int = x + 1 }

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