fixes a problem with an extractor object overloaded by a regular def

Author: xeno-by

src/compiler/scala/reflect/internal/Types.scala

@@ -2663,6 +2663,10 @@ trait Types extends api.Types { self: SymbolTable =>
     override def kind = "OverloadedType"
   }
 
+  def overloadedType(pre: Type, alternatives: List[Symbol]): Type =
+    if (alternatives.tail.isEmpty) pre memberType alternatives.head
+    else OverloadedType(pre, alternatives)
+
   /** A class remembering a type instantiation for some a set of overloaded
    *  polymorphic symbols.
    *  Not used after phase `typer`.

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -958,9 +958,14 @@ trait Typers extends Modes with Adaptations with Taggings {
        * see test/files/../t5189*.scala
        */
       def adaptConstrPattern(): Tree = { // (5)
-        val extractor = tree.symbol.filter(sym => reallyExists(unapplyMember(sym.tpe)))
+        def isExtractor(sym: Symbol) = reallyExists(unapplyMember(sym.tpe))
+        val extractor = tree.symbol filter isExtractor
         if (extractor != NoSymbol) {
           tree setSymbol extractor
+          tree.tpe match {
+            case OverloadedType(pre, alts) => tree.tpe = overloadedType(pre, alts filter isExtractor)
+            case _ =>
+          }
           val unapply = unapplyMember(extractor.tpe)
           val clazz = unapplyParameterType(unapply)
 

test/files/pos/overloaded_extractor_and_regular_def.scala

@@ -0,0 +1,32 @@
+trait TreesBase {
+  type Tree
+
+  type Apply <: Tree
+
+  val Apply: ApplyExtractor
+
+  abstract class ApplyExtractor {
+    def apply(x: Int): Apply
+    def unapply(apply: Apply): Option[Int]
+  }
+}
+
+trait TreesApi extends TreesBase {
+  def Apply(x: String)
+}
+
+class Universe extends TreesApi {
+  abstract class Tree
+  case class Apply(x: Int) extends Tree
+  object Apply extends ApplyExtractor
+  def Apply(x: String) = Apply(x.toInt)
+}
+
+object Test extends App {
+  def foo(tapi: TreesApi) {
+    import tapi._
+    def bar(tree: Tree) {
+      val Apply(x) = tree
+    }
+  }
+}