[Foundation] NSSet, NSDictionary: Use as! casts to force-bridge elements

This traps with a clear runtime error on failure, rather than simply crashing in the runtime.

Author: lorentey

stdlib/public/Darwin/Foundation/NSDictionary.swift

@@ -136,7 +136,7 @@ extension Dictionary : _ObjectiveCBridgeable {
     to: T.Type
   ) {
     for i in (0..<count).reversed() {
-      let bridged = Swift._forceBridgeFromObjectiveC(buffer[i], T.self)
+      let bridged = buffer[i] as! T
       _bridgeInitialize(index: i, of: buffer, to: bridged)
     }
   }
@@ -225,8 +225,8 @@ extension Dictionary : _ObjectiveCBridgeable {
         let anyObjectKey = anyKey as AnyObject
         let anyObjectValue = anyValue as AnyObject
         builder.add(
-            key: Swift._forceBridgeFromObjectiveC(anyObjectKey, Key.self),
-            value: Swift._forceBridgeFromObjectiveC(anyObjectValue, Value.self))
+          key: anyObjectKey as! Key,
+          value: anyObjectValue as! Value)
       })
       result = builder.take()
     } else {

stdlib/public/Darwin/Foundation/NSSet.swift

@@ -77,10 +77,8 @@ extension Set : _ObjectiveCBridgeable {
       // Swift. See rdar://problem/35995647
       var set = Set(minimumCapacity: s.count)
       s.enumerateObjects({ (anyMember: Any, _) in
-        let member = Swift._forceBridgeFromObjectiveC(
-          anyMember as AnyObject, Element.self)
         // FIXME: Log a warning if `member` is already in the set.
-        set.insert(member)
+        set.insert(anyMember as AnyObject as! Element)
       })
       result = set
       return
@@ -90,8 +88,7 @@ extension Set : _ObjectiveCBridgeable {
     // an NSSet.
     var builder = _SetBuilder<Element>(count: s.count)
     s.enumerateObjects({ (anyMember: Any, _) in
-      builder.add(member: Swift._forceBridgeFromObjectiveC(
-        anyMember as AnyObject, Element.self))
+      builder.add(member: anyMember as AnyObject as! Element)
     })
     result = builder.take()
   }