Add testcases for use annotations and value classes

Author: Linyxus

tests/neg-custom-args/captures/cc-annot-value-classes.scala

@@ -0,0 +1,18 @@
+import language.experimental.captureChecking
+import caps.*
+
+class Runner(val x: Int) extends AnyVal:
+  def runOps(@use ops: List[() => Unit]): Unit =
+    ops.foreach(_())  // ok
+
+class RunnerAlt(val x: Int):
+  def runOps(@use ops: List[() => Unit]): Unit =
+    ops.foreach(_())  // ok, of course
+
+class RunnerAltAlt(val x: Int) extends AnyVal:
+  def runOps(ops: List[() => Unit]): Unit =
+    ops.foreach(_())  // error, as expected
+
+class RunnerAltAltAlt(val x: Int):
+  def runOps(ops: List[() => Unit]): Unit =
+    ops.foreach(_())  // error, as expected

tests/pos-custom-args/captures/cc-use-iterable.scala

@@ -0,0 +1,10 @@
+import language.experimental.captureChecking
+trait IterableOnce[+T]
+trait Iterable[+T] extends IterableOnce[T]:
+  def flatMap[U](@caps.use f: T => IterableOnce[U]^): Iterable[U]^{this, f*}
+
+
+class IterableOnceExtensionMethods[T](val it: IterableOnce[T]) extends AnyVal:
+  def flatMap[U](@caps.use f: T => IterableOnce[U]^): IterableOnce[U]^{f*} = it match
+    case it: Iterable[T] => it.flatMap(f)
+