Rewrite reaches tests to fix tasty-cc nightly failures

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

@@ -41,3 +41,8 @@
    |                         Required: File^{id*}
    |
    | longer explanation available when compiling with `-explain`
+-- Error: tests/neg-custom-args/captures/reaches.scala:77:5 ------------------------------------------------------------
+77 |  ps.map((x, y) => compose1(x, y)) // error: cannot mix cap and *
+   |  ^^^^^^
+   |  Reach capability cap and universal capability cap cannot both
+   |  appear in the type [B](f: ((box A ->{ps*} A, box A ->{ps*} A)) => B): List[B] of this expression

tests/neg-custom-args/captures/reaches.scala

@@ -59,3 +59,21 @@ def attack2 =
   val leaked = usingFile[File^{id*}]: f =>
     val f1: File^{id*} = id(f) // error
     f1
+
+class List[+A]:
+  def head: A = ???
+  def tail: List[A] = ???
+  def map[B](f: A => B): List[B] = ???
+  def nonEmpty: Boolean = ???
+
+extension [A](x: A) def :: (xs: List[A]): List[A] = ???
+
+object Nil extends List[Nothing]
+
+def compose1[A, B, C](f: A => B, g: B => C): A ->{f, g} C =
+  z => g(f(z))
+
+def mapCompose[A](ps: List[(A => A, A => A)]): List[A ->{ps*} A] =
+  ps.map((x, y) => compose1(x, y)) // error: cannot mix cap and *
+
+

tests/pos-custom-args/captures/reaches.scala

@@ -10,6 +10,16 @@ class Ref[T](init: T):
   def get: T = x
   def set(y: T) = { x = y }
 
+class List[+A]:
+  def head: A = ???
+  def tail: List[A] = ???
+  def map[B](f: A -> B): List[B] = ???
+  def nonEmpty: Boolean = ???
+
+extension [A](x: A) def :: (xs: List[A]): List[A] = ???
+
+object Nil extends List[Nothing]
+
 def runAll(xs: List[Proc]): Unit =
   var cur: List[() ->{xs*} Unit] = xs  // OK, by revised VAR
   while cur.nonEmpty do
@@ -36,7 +46,7 @@ def compose2[A, B, C](f: A => B, g: B => C): A => C =
   z => g(f(z))
 
 def mapCompose[A](ps: List[(A => A, A => A)]): List[A ->{ps*} A] =
-  ps.map((x, y) => compose1(x, y))
+  ps.map((x, y) => compose1(x, y)) // Does not work if map takes an impure function, see reaches in neg
 
 @annotation.capability class IO