Virtual package provided by libssreflect-coq Formula was removed
Last version was

Revision: 3

ssreflect requires the following formulae to be installed:
ocaml 4.06.1 General purpose programming language in the ML family
menhir 20171222 LR(1) parser generator for the OCaml programming language
camlp5 7.05_1 Preprocessor and pretty-printer for OCaml

Recent formula history

Kasumi Hanazuki math-comp 1.6.4
ilovezfs ssreflect: set safe-string=0 for OCaml 4.06.0 compat
ilovezfs Use “squiggly” heredocs.
ilovezfs ssreflect: revision for ocaml
ilovezfs ssreflect: update homepage (#10313)

Formula code at GitHub