The ghc-mod command

ghc-mod list
Displays a list of modules
ghc-mod lang
Displays a list of language extensions
ghc-mod flag
Displays a list of GHC flags
ghc-mod browse [<package>:]<module>
Displays symbols of <module>
ghc-mod check <HaskellFile>
Checks syntax with GHC
ghc-mod expand <HaskellFile>
Expands Template Haskell
ghc-mod debug <HaskellFile>
Displays debug information
ghc-mod info <HaskellFile> <module> <expression>
Displays information about the expression
ghc-mod type <HaskellFile> <module> <line-no> <column-no>
Displays the types of all expressions including the expression
ghc-mod find <symbol>
Finds all module names exporting <symbol>
ghc-mod lint <HaskellFile>
Checks synstax with Hlint
ghc-mod root <HaskellFile>
Finds the root directory for the Haskell file
ghc-mod doc <module>
Finds the html document for the module
ghc-mod boot
Displays boot information for Emacs front-end
ghc-mod version
Displays the version of ghc-mod
ghc-mod help
Displays help messages

<module> for "info" and "type" is not used, anything is OK. It is necessary to maintain backward compatibility.