Are you filing an issue about iOS 12?
No

Describe the bug
OIDEndSessionRequest.h brackets its declarations with NS_ASSUME_NONNULL, which means that all object-typed parameters will be bridged into Swift as non-optional, unless otherwise specified.

The initializers to create an OIDEndSessionRequest allow you to pass in an idTokenHint:(NSString *)idTokenHint parameter, which lacks the nullable specifier. This means that in Swift, that parameter is bridged as String, and not String?.

The @property for this parameter correctly shows it as nullable, and the implementation allows for the underlying ivar to be nil, which means the initializer parameter should allow nil values as well.

The same applies to the postLogoutRedirectURL:(NSURL *)postLogoutRedirectURL and state:(NSString *)state parameters.

Expected behavior
These initializer parameters are declared as (nullable NS... *):