Add capture checking to CommandLineParser

Author: natsukagami

library/src/scala/util/CommandLineParser.scala

@@ -1,5 +1,7 @@
 package scala.util
 
+import language.experimental.captureChecking
+
 /** A utility object to support command line parsing for @main methods */
 object CommandLineParser {
 
@@ -12,7 +14,7 @@ object CommandLineParser {
   /** Parse command line argument `s`, which has index `n`, as a value of type `T`
    *  @throws ParseError if argument cannot be converted to type `T`.
    */
-  def parseString[T](str: String, n: Int)(using fs: FromString[T]): T = {
+  def parseString[T](str: String, n: Int)(using fs: FromString[T]^): T = {
     try fs.fromString(str)
     catch {
       case ex: IllegalArgumentException => throw ParseError(n, ex.toString)
@@ -22,14 +24,14 @@ object CommandLineParser {
   /** Parse `n`'th argument in `args` (counting from 0) as a value of type `T`
    *  @throws ParseError if argument does not exist or cannot be converted to type `T`.
    */
-  def parseArgument[T](args: Array[String], n: Int)(using fs: FromString[T]): T =
+  def parseArgument[T](args: Array[String], n: Int)(using fs: FromString[T]^): T =
     if n < args.length then parseString(args(n), n)
     else throw ParseError(n, "more arguments expected")
 
   /** Parse all arguments from `n`'th one (counting from 0) as a list of values of type `T`
    *  @throws ParseError if some of the arguments cannot be converted to type `T`.
    */
-  def parseRemainingArguments[T](args: Array[String], n: Int)(using fs: FromString[T]): List[T] =
+  def parseRemainingArguments[T](args: Array[String], n: Int)(using fs: FromString[T]^): List[T] =
     if n < args.length then parseString(args(n), n) :: parseRemainingArguments(args, n + 1)
     else Nil