hdevtools is a backend for text editor plugins, to allow for things such as
syntax and type checking of Haskell code, and retrieving type information, all
directly from within your text editor.
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The advantage that hdevtools has over ghc-mod is that it runs silently
in a persistent background process, and therefore is able to keeps all of your
Haskell modules and dependent libraries loaded in memory. This way, when you
change only a single source file, only it needs to be reloaded and rechecked,
instead of having to reload everything.
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This makes hdevtools very fast for checking syntax and type errors (runs
just as fast as the ":reload" command in GHCi).
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In fact, syntax and type checking is so fast, that you can safely enable auto
checking on every save. Even for huge projects, checking is nearly instant.
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In addition to checking Haskell source code for errors, `hdevtools` has tools
for getting info about identifiers, and getting type information for snippets
of code.
