stdlib: Address new #StrictMemorySafety warnings.

Author: tshortli

stdlib/public/core/StringBridge.swift

@@ -119,7 +119,7 @@ private func _stdlib_binary_createIndirectTaggedPointerNSString(
   ptr: UnsafePointer<UInt8>,
   count: Int
 ) -> UnsafeRawPointer? {
-  return _swift_stdlib_CreateIndirectTaggedPointerString(ptr, count);
+  return unsafe _swift_stdlib_CreateIndirectTaggedPointerString(ptr, count);
 }
 
 @usableFromInline // @testable
@@ -631,12 +631,12 @@ extension String {
     }
     if _guts._object.isImmortal && !_guts._object.largeFastIsConstantCocoa {
       if _guts.isASCII && _guts._object.isFastZeroTerminated {
-        let ptr = _guts._object.fastUTF8.baseAddress!
+        let ptr = unsafe _guts._object.fastUTF8.baseAddress!
         let count = _guts.count
-        if let indirect = _stdlib_binary_createIndirectTaggedPointerNSString(
+        if let indirect = unsafe _stdlib_binary_createIndirectTaggedPointerNSString(
           ptr: ptr, count: count
         ) {
-          return unsafeBitCast(indirect, to: AnyObject.self)
+          return unsafe unsafeBitCast(indirect, to: AnyObject.self)
         }
       }
       let gutsCountAndFlags = _guts._object._countAndFlags

stdlib/public/core/Substring.swift

@@ -782,7 +782,7 @@ extension Substring.UTF8View {
         let base: String.UTF8View = self._base
         let first = base._foreignDistance(from: base.startIndex, to: startIndex)
         let count = base._foreignDistance(from: startIndex, to: endIndex)
-        let span = unsafe base.span._extracting(first..<(first &+ count))
+        let span = base.span._extracting(first..<(first &+ count))
         return unsafe _overrideLifetime(span, borrowing: self)
       }
 #endif