Fix #3585: Add missing changeOwner when building lazy implicits

Author: odersky

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

@@ -635,7 +635,9 @@ trait Implicits { self: Typer =>
           case _ => false
         }
         if (lazyImplicit.exists && refersToLazyImplicit)
-          Block(ValDef(lazyImplicit.asTerm, arg).withPos(pos) :: Nil, ref(lazyImplicit))
+          Block(
+            ValDef(lazyImplicit.asTerm, arg.changeOwner(ctx.owner, lazyImplicit)).withPos(pos) :: Nil,
+            ref(lazyImplicit))
         else
           arg
       case fail @ SearchFailure(tree) =>

tests/pos/i3585.scala

@@ -0,0 +1,16 @@
+trait Foo[T]
+
+object Foo {
+  implicit def pair[T, U]
+    (implicit
+      fooT: => Foo[(T, U)],
+      fooU: => Foo[(U, T)]
+    ): Foo[(T, U)] = ???
+
+  implicit def int: Foo[Int] = ???
+  implicit def string: Foo[String] = ???
+}
+
+object Test extends App {
+  implicitly[Foo[(Int, String)]]
+}