Inconsistent behavior of GRANT/REVOKE PROXY with roles

create user u1;

create user u2;

create role r1;

create role r2;

grant proxy on u1 to u2;

grant proxy on u1 to CURRENT_USER;

grant proxy on CURRENT_USER to u2;

set role r1;

# This does not work: a role cannot be granted proxy on a user

# (returns ERROR 1133 Can't find any matching row in the user table)

grant proxy on u1 to r1;

# This also does not work, same error, so it's consistent with the previous one

# (also returns ERROR 1133 Can't find any matching row in the user table)

grant proxy on u1 to CURRENT_ROLE;

# This works (I'm not sure it should, but it does): a user can be granted proxy on a role

grant proxy on r1 to u2;

# But this returns a syntax error

grant proxy on CURRENT_ROLE to u1;