Full name of submitter (unless configured in github; will be published with the issue): Davis Herring

Reference (section label): dcl.fct 9.3.4.6

Link to reflector thread (if any): cplusplus/draft#4521

Issue description:

It should have a defining-type-specifier-seq instead of a decl-specifier-seq, since no other decl-specifier (a storage-class-specifier, a function-specifier, friend, typedef, constexpr, consteval, constinit, or inline) can be used there (unless we expect to get constexpr function parameters any day now!).

Suggested resolution: