Feature Request: Custom errors via type param utility when used as a default #41392

type IsValid<T> = // ... the predicate type

type WithComplexConstraint<
  InQuestion, // <-- the type in need of validation
  DidThrow = ParamError<"That's invalid!", InQuestion, IsValid<InQuestion> ? false : true>
  //                    ^                  ^           ^
  //                    |                  |           |
  //                    |                  |           3. A boolean representing whether or not to error)
  //                    |                  2. The type param over which to display the error
  //                    1. The error message
> = // ...

type IsEmailAddress<S extends string> = // ...

declare function acceptsEmailAddress<
  S extends string,
  IsInvalid = ParamError<"The supplied string type is not an email address type.", S, IsEmailAddress<S>>
>(emailAddress: S): void;

acceptsEmailAddress("rickross@smoothrapping.com");
acceptsEmailAddress("toppotdoughnuts.com");
//                   ~~~~~~~~~~~~~~~~~~~~
//                   ^
//                   type-error: "The supplied string type is not an email address type."

type IsEmailAddress<S extends string> = // ...
type IsHotmailDotCom<S extends string> = S extends `${infer Local}@hotmail.com` ? true : false;

declare function acceptsEmailAddress<
  S extends string,
  IsInvalid = ParamError<"The supplied string type is not an email address type.", S, IsEmailAddress<S>>,
  IsHotmail = ParamError<"I respect it, but cummon... hotmail... in 2020? You still playing Neopets too?", S, IsHotmailDotCom<S>>
>(emailAddress: S): void;

acceptsEmailAddress("rickyrose@hotmail.com");
//                  ~~~~~~~~~~~~~~~~~~~~~~
//                  ^
//                  type-error: "The supplied string type is not an email address type."
//                  type-error: "I respect it, but cummon... hotmail... in 2020? You still playing Neopets too?"

type IsValidLocal<S> extends string = // ...
type IsValidDomain<S extends string> = // ...
type IsValidExtension<S extends string> = // ...

type AllTrue<T extends boolean[]> = // ...

type IsEmail<S extends string> = S extends `${infer Local}@${infer Domain}.${infer Extension}`
  ? AllTrue<[IsValidLocal<Local>, IsValidDomain<Domain>, IsValidExtension<Extension>]>
  : false;

type EmailAddress = // ... somehow with the constraints defined above

declare function acceptsEmailAddress(emailAddress: EmailAddress): void;

declare function acceptsEmailAddress(emailAddress: string): void;

const emailAddress = "rick@ross.com";
acceptsEmailAddress(emailAddress);

type EmailAddress = typeof emailAddress;
type UsedCorrectly = IsEmailAddress<EmailAddress>;
assert<IsExact<UsedCorrectly, true>>(true); // using `conditional-type-checks`

type Error<Message extends string> = {error: Message};

declare function acceptsEmailAddress<E extends string>(emailAddress: E): IsEmailAddress<E> extends true ? Error<"Invalid email address supplied"> : string;

const emailAddress = "rick@ross.com";
const result = acceptsEmailAddress(emailAddress);

declare function acceptsResult(result: string): void;

acceptsResult(result); // throws a type error if `emailAddress`'s type does not pass the `IsEmail` check