[stdlib] Add a transparent specialization of ~= for Range

Making the generic ~= transparent does not help unoptimized code; adding a specialization does.

Author: lorentey

stdlib/public/core/Range.swift

@@ -96,7 +96,35 @@ extension RangeExpression {
  @inlinable
  public static func ~= (pattern: Self, value: Bound) -> Bool {
  return pattern.contains(value)
- } 
+ }
+}
+
+extension Range {
+ /// Returns a Boolean value indicating whether a value is included in a
+ /// range.
+ ///
+ /// You can use the pattern-matching operator (`~=`) to test whether a value
+ /// is included in a range. The pattern-matching operator is used
+ /// internally in `case` statements for pattern matching. The following
+ /// example uses the `~=` operator to test whether an integer is included in
+ /// a range of single-digit numbers:
+ ///
+ /// let chosenNumber = 3
+ /// if 0..<10 ~= chosenNumber {
+ /// print("\(chosenNumber) is a single digit.")
+ /// }
+ /// // Prints "3 is a single digit."
+ ///
+ /// - Parameters:
+ /// - pattern: A range.
+ /// - bound: A value to match against `pattern`.
+ @_transparent
+ public static func ~= (pattern: Self, value: Bound) -> Bool {
+ // Note: `Range.~=` is used particularly frequently to implement bounds
+ // checks. This more specific variant of the generic `=~` is intended to
+ // help improve unoptimized performance of these cases.
+ pattern.contains(value)
+ }
 }
 
 /// A half-open interval from a lower bound up to, but not including, an upper