Make apply proxies work with overloaded ctors

Author: dwijnand

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

@@ -4298,7 +4298,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
  }
 
  /** Convert constructor proxy reference to a new expression */
- def newExpr =
+ def newExpr(ctorResultType: Type) =
  val qual = qualifier(tree)
  val tpt = qual match
  case Ident(name) =>
@@ -4309,17 +4309,22 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
  cpy.Ident(qual)(qual.symbol.name.sourceModuleName.toTypeName)
  case _ =>
  errorTree(tree, em"cannot convert from $tree to an instance creation expression")
- val tycon = tree.tpe.widen.finalResultType.underlyingClassRef(refinementOK = false)
+ val tycon = ctorResultType.underlyingClassRef(refinementOK = false)
  typed(
  untpd.Select(
  untpd.New(untpd.TypedSplice(tpt.withType(tycon))),
  nme.CONSTRUCTOR),
  pt)
  .showing(i"convert creator $tree -> $result", typr)
 
- def isApplyProxy(tree: Tree) = tree match
- case Select(_, nme.apply) => tree.symbol.isAllOf(ApplyProxyFlags)
- case _ => false
+ def applyProxy(tree: Tree) = tree match
+ case Select(_, nme.apply) =>
+ tree.denot.altsWith(_.isAllOf(ApplyProxyFlags)) match
+ case denot :: _ =>
+ // any of the constructors will do, in order to get the result type, so using the first one
+ denot.info.widen.finalResultType
+ case _ => NoType
+ case _ => NoType
 
  tree match {
  case _: MemberDef | _: PackageDef | _: Import | _: WithoutTypeOrPos[?] | _: Closure => tree
@@ -4333,7 +4338,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
  if needsTupledDual(ref, pt) && Feature.autoTuplingEnabled =>
  adapt(tree, pt.tupledDual, locked)
  case _ =>
- adaptOverloaded(ref)
+ val ctorResultType = applyProxy(tree)
+ if ctorResultType.exists then newExpr(ctorResultType)
+ else adaptOverloaded(ref)
  }
  case poly: PolyType
  if !(ctx.mode is Mode.Type) && dummyTreeOfType.unapply(tree).isEmpty =>
@@ -4342,7 +4349,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
  // Test case was but i18695.scala, but it got fixed by a different tweak in #18719.
  // We leave test for this condition in as a defensive measure in case
  // it arises somewhere else.
- if isApplyProxy(tree) then newExpr
+ val ctorResultType = applyProxy(tree)
+ if ctorResultType.exists then newExpr(ctorResultType)
  else if pt.isInstanceOf[PolyProto] then tree
  else
  var typeArgs = tree match
@@ -4356,7 +4364,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
  readaptSimplified(handleStructural(tree))
  else pt match {
  case pt: FunProto =>
- if isApplyProxy(tree) then newExpr
+ val ctorResultType = applyProxy(tree)
+ if ctorResultType.exists then newExpr(ctorResultType)
  else adaptToArgs(wtp, pt)
  case pt: PolyProto if !wtp.isImplicitMethod =>
  tryInsertApplyOrImplicit(tree, pt, locked)(tree) // error will be reported in typedTypeApply

tests/pos/i19201.scala

@@ -0,0 +1,12 @@
+class Person(
+ val firstName: String,
+ val lastName: String,
+ val birthYear: Int = -1,
+ val address: String = ""
+):
+ // Works if remove this constructor
+ def this() = this("John", "Doe")
+
+class Test:
+ def p1 = Person("First", "Last") // was: Type Error: none of the overloads.. match arguments
+ def p2 = Person("Josh", "Joe", 1912, "Main Street")