[stdlib] ClosedRange.contains: Leave this force-inlined, not transparent

Making it transparent evidently induces new retain/release traffic in Array’s subscript, even though I can find no indication that `ClosedRange.contains` is ever called by that code path. Oh well.

Author: lorentey

stdlib/public/core/ClosedRange.swift

@@ -128,7 +128,8 @@ extension ClosedRange: RangeExpression {
   /// - Parameter element: The element to check for containment.
   /// - Returns: `true` if `element` is contained in the range; otherwise,
   ///   `false`.
-  @_transparent
+  @inlinable
+  @inline(__always)
   public func contains(_ element: Bound) -> Bool {
     return element >= self.lowerBound && element <= self.upperBound
   }

stdlib/public/core/Range.swift

@@ -1080,7 +1080,7 @@ extension Range {
     other.isEmpty ||
       (lowerBound <= other.lowerBound && upperBound >= other.upperBound)
   }
-  
+
   /// Returns a Boolean value indicating whether the given closed range is
   /// contained within this range.
   ///

test/stdlib/RangeContainsInlining.swift

@@ -2,10 +2,9 @@
 // RUN: %target-swift-emit-ir -primary-file %s -O 2>&1 | %FileCheck --check-prefixes CHECK,CHECK-OPTIMIZED %s
 // RUN: %target-swift-emit-ir -primary-file %s -Osize 2>&1 | %FileCheck --check-prefixes CHECK,CHECK-OPTIMIZED %s
 
-// We expect calls to `Range.contains`, `ClosedRange.contains` over a
-// `Range` instance to result in direct bound comparisons in all compilation
-// modes, including unoptimized builds. (These are often used to implement
-// bounds checking.)
+// We expect calls to `Range.contains` to result in direct bound comparisons in
+// all compilation modes, including unoptimized builds. (These are often used to
+// implement bounds checking.)
 //
 // The sample functions below use bounds of different integer types to avoid
 // them tail-calling each other.
@@ -19,11 +18,14 @@ public func halfOpenContains(_ r: Range<Int8>, _ i: Int8) -> Bool {
   r.contains(i)
 }
 
-// CHECK-LABEL: define  {{.*}} i1 @"$s21RangeContainsInlining06closedB0ySbSNys5Int16VG_ADtF"
-// CHECK-NOT: call swiftcc
-// CHECK: icmp
-// CHECK-NOT: call swiftcc
-// CHECK-LABEL: {{^}}}
+// `ClosedRange.contains is only marked `@inline(__always)`; unfortunately it
+// doesn't get inlined in deug builds.
+
+// CHECK-OPTIMIZED-LABEL: define  {{.*}} i1 @"$s21RangeContainsInlining06closedB0ySbSNys5Int16VG_ADtF"
+// CHECK-OPTIMIZED-NOT: call swiftcc
+// CHECK-OPTIMIZED: icmp
+// CHECK-OPTIMIZED-NOT: call swiftcc
+// CHECK-OPTIMIZED-LABEL: {{^}}}
 public func closedContains(_ r: ClosedRange<Int16>, _ i: Int16) -> Bool {
   r.contains(i)
 }