[stdlib] Postpone generalizing Result.flatMapError

Author: lorentey

stdlib/public/core/Result.swift

@@ -252,7 +252,10 @@ extension Result where Success: ~Copyable {
   }
 }
 
-extension Result where Success: ~Copyable & ~Escapable {
+extension Result where Success: ~Copyable {
+  // FIXME: This should allow ~Escapable Success types
+  // (https://forums.swift.org/t/se-0465-standard-library-primitives-for-nonescapable-types/78310/5)
+
   /// Returns a new result, mapping any failure value using the given
   /// transformation and unwrapping the produced result.
   ///

test/api-digester/Outputs/stability-stdlib-source-base.swift.expected

@@ -331,7 +331,7 @@ Func Optional.flatMap(_:) is now without rethrows
 Func Optional.map(_:) has generic signature change from <Wrapped, U> to <Wrapped, E, U where E : Swift.Error, U : ~Copyable>
 Func Optional.map(_:) is now without rethrows
 Func Result.flatMap(_:) has generic signature change from <Success, Failure, NewSuccess where Failure : Swift.Error> to <Success, Failure, NewSuccess where Failure : Swift.Error, NewSuccess : ~Copyable>
-Func Result.flatMapError(_:) has generic signature change from <Success, Failure, NewFailure where Failure : Swift.Error, NewFailure : Swift.Error> to <Success, Failure, NewFailure where Failure : Swift.Error, NewFailure : Swift.Error, Success : ~Copyable, Success : ~Escapable>
+Func Result.flatMapError(_:) has generic signature change from <Success, Failure, NewFailure where Failure : Swift.Error, NewFailure : Swift.Error> to <Success, Failure, NewFailure where Failure : Swift.Error, NewFailure : Swift.Error, Success : ~Copyable>
 Func Result.flatMapError(_:) has self access kind changing from NonMutating to Consuming
 Func Result.map(_:) has generic signature change from <Success, Failure, NewSuccess where Failure : Swift.Error> to <Success, Failure, NewSuccess where Failure : Swift.Error, NewSuccess : ~Copyable>
 Func Result.mapError(_:) has generic signature change from <Success, Failure, NewFailure where Failure : Swift.Error, NewFailure : Swift.Error> to <Success, Failure, NewFailure where Failure : Swift.Error, NewFailure : Swift.Error, Success : ~Copyable, Success : ~Escapable>