The following bug has been logged on the website:

Bug reference: 15802
Logged by: David Binderman
Email address: dcb314(at)hotmail(dot)com
PostgreSQL version: 11.3
Operating system: Linux
Description:

postgresql-11.3/src/interfaces/libpq/fe-misc.c:1060]: (style) Comparison of
a function returning boolean value using relational (<, >, <= or >=)
operator.

Source code is

if (forRead && conn->ssl_in_use && pgtls_read_pending(conn) > 0)

but

./src/interfaces/libpq/libpq-int.h:extern bool pgtls_read_pending(PGconn
*conn);