[stdlib] Refactor Range Overlaps for Performance

stdlib/public/core/ClosedRange.swift

@@ -444,7 +444,12 @@ extension ClosedRange where Bound: Strideable, Bound.Stride : SignedInteger {
 extension ClosedRange {
   @inlinable
   public func overlaps(_ other: ClosedRange<Bound>) -> Bool {
-    return self.contains(other.lowerBound) || other.contains(lowerBound)
+    // Disjoint iff the other range is completely before or after our range.
+    // Unlike a `Range`, a `ClosedRange` can *not* be empty, so no check for
+    // that case is needed here.
+    let isDisjoint = other.upperBound < self.lowerBound
+      || self.upperBound < other.lowerBound
+    return !isDisjoint
   }
 
   @inlinable

stdlib/public/core/Range.swift

@@ -943,14 +943,26 @@ extension Range {
   ///   common; otherwise, `false`.
   @inlinable
   public func overlaps(_ other: Range<Bound>) -> Bool {
-    return (!other.isEmpty && self.contains(other.lowerBound))
-        || (!self.isEmpty && other.contains(self.lowerBound))
+    // Disjoint iff the other range is completely before or after our range.
+    // Additionally either `Range` (unlike a `ClosedRange`) could be empty, in
+    // which case it is disjoint with everything as overlap is defined as having
+    // an element in common.
+    let isDisjoint = other.upperBound <= self.lowerBound
+      || self.upperBound <= other.lowerBound
+      || self.isEmpty || other.isEmpty
+    return !isDisjoint
   }
 
   @inlinable
   public func overlaps(_ other: ClosedRange<Bound>) -> Bool {
-    return self.contains(other.lowerBound)
-        || (!self.isEmpty && other.contains(self.lowerBound))
+    // Disjoint iff the other range is completely before or after our range.
+    // Additionally the `Range` (unlike the `ClosedRange`) could be empty, in
+    // which case it is disjoint with everything as overlap is defined as having
+    // an element in common.
+    let isDisjoint = other.upperBound < self.lowerBound
+      || self.upperBound <= other.lowerBound
+      || self.isEmpty
+    return !isDisjoint
   }
 }