Use refmt to display syntax error messages for your Reason code in Atom.
Just install and enable the package
This package requires language-reason and the latest version of the reason-cli tools.
Other recommended packages:
With nuclide
apm install language-reason linter-refmt
Without nuclide
apm install language-reason linter-refmt linter
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.