Don't box arguments of inferred applied types at Setup

Rely on auto-boxing when accessing the arguments instead

Author: odersky

compiler/src/dotty/tools/dotc/cc/Setup.scala

@@ -209,7 +209,7 @@ extends tpd.TreeTraverser:
             else
               tp.derivedAppliedType(tycon1, args1 :+ res1)
           else
-            tp.derivedAppliedType(tycon1, args.mapConserve(arg => box(this(arg))))
+            tp.derivedAppliedType(tycon1, args.mapConserve(arg => this(arg)))
         case tp @ RefinedType(core, rname, rinfo) if defn.isFunctionType(tp) =>
           val rinfo1 = apply(rinfo)
           if rinfo1 ne rinfo then rinfo1.toFunctionType(isJava = false, alwaysDependent = true)

tests/neg-custom-args/captures/lazylist.check

@@ -37,6 +37,6 @@
 17 |  def tail = xs() // error: cannot have an inferred type
    |  ^^^^^^^^^^^^^^^
    |  Non-local method tail cannot have an inferred result type
-   |  {LazyCons.this.xs} lazylists.LazyList[box ? T]
+   |  {LazyCons.this.xs} lazylists.LazyList[? T]
    |  with non-empty capture set {LazyCons.this.xs}.
    |  The type needs to be declared explicitly.

tests/neg-custom-args/captures/lazylists2.check

@@ -8,7 +8,7 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylists2.scala:18:4 ------------------------------------
 18 |    final class Mapped extends LazyList[B]:  // error
    |    ^
-   |    Found:    {f, xs} LazyList[box ? B]
+   |    Found:    {f, xs} LazyList[? B]
    |    Required: {f} LazyList[B]
 19 |      this: ({xs, f} Mapped) =>
 20 |      def isEmpty = false
@@ -20,7 +20,7 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylists2.scala:27:4 ------------------------------------
 27 |    final class Mapped extends LazyList[B]:  // error
    |    ^
-   |    Found:    {f, xs} LazyList[box ? B]
+   |    Found:    {f, xs} LazyList[? B]
    |    Required: {xs} LazyList[B]
 28 |      this: ({xs, f} Mapped) =>
 29 |      def isEmpty = false

tests/neg-custom-args/captures/try.check

@@ -1,8 +1,8 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/try.scala:23:49 ------------------------------------------
 23 |  val a = handle[Exception, CanThrow[Exception]] { // error
    |                                                 ^
-   |                              Found:    ? ({*} CT[Exception]) -> {*} CT[? >: box ? Exception <: box ? Exception]
-   |                              Required: CanThrow[Exception] => box {*} CT[Exception]
+   |                                      Found:    ? ({*} CT[Exception]) -> {*} CT[? >: ? Exception <: ? Exception]
+   |                                      Required: CanThrow[Exception] => box {*} CT[Exception]
 24 |    (x: CanThrow[Exception]) => x
 25 |  }{
    |