Function: SB-EXT:VALID-TYPE-SPECIFIER-P

Returns T if TYPE-SPECIFIER is a valid type specifier, otherwise NIL.

There may be different metrics on what constitutes a “valid type specifier” depending on context. If this function does not suit your exact need, you may be able to craft a particular solution using a combination of DEFINED-TYPE-NAME-P and the TYPEXPAND functions.

The definition of “valid type specifier” employed by this function is based on the following mnemonic:

“Would TYPEP accept it as second argument?”

Except that unlike TYPEP, this function fully supports compound FUNCTION type specifiers, and the VALUES type specifier, too.

In particular, VALID-TYPE-SPECIFIER-P will return NIL if TYPE-SPECIFIER is not a class, not a symbol that is known to name a type specifier, and not a cons that represents a known compound type specifier in a syntactically and recursively correct way.

Examples:

(valid-type-specifier-p ‘(cons * *)) => T (valid-type-specifier-p ‘#:foo) => NIL (valid-type-specifier-p ‘(cons * #:foo)) => NIL (valid-type-specifier-p ‘(cons 1 *) => NIL

Experimental.

Lambda list

(sb-kernel:type-specifier &optional sb-kernel::env)