Haskell Support in Maguyva: Code Graphs for Type Classes and Modules

Where Haskell trips up shallow AI tools

Haskell calls functions without parentheses, composes them with operators, and dispatches through type classes. render user is a call, f . g <$> xs holds several, and show means whatever the instance for that type says. Text search finds the names, not the instances behind them.

Maguyva records instances and constructors as relationships, so an agent can see which types implement a class and where a value is built.

What Maguyva extracts in Haskell

Maguyva maps .hs and .lhs files to Haskell. Functions and bindings are extracted as callables, and type classes, data types, and newtypes as types. Calls are recognised in space-separated application and through infix operators, and imports normalise qualified, hiding, and as clauses.

Type classes and constructors become graph relationships:

• instance Eq Point records that Point implements Eq.
• When a class method has a default body in the same file, an instance that defines that method records an override of the default.
• Applying a data constructor, such as Point 1 2, counts as instantiation.
• error, undefined, and throw record throws, and handlers such as catch record catches.

Because instance declarations can define names such as show or return, a same-file definition is not assumed to be the target of a bare call with that name.

Example agent prompts

• “Who calls parseConfig, and from which modules?” (find_symbol, then dependency_search incoming)
• “Which types have a ToJSON instance?” (dependency_search)
• “Trace how a request is decoded and validated.” (get_task_context)

Known limits

• About 130 Prelude and base names, such as map, foldr, fmap, pure, and >>=, and modules such as Data.List and Control.Monad, are filtered from relationships. Use text_pattern_search for them.
• In the grammar, a raw function node also denotes function types, so the functions preset in structural_search returns lambdas only, and the methods and variables presets select nothing. Use find_symbol for named functions.
• Literate .lhs files are read with the Haskell grammar as a whole, so expect partial results for them.
• Haskell has no decorator syntax, so decorator relationships are marked not applicable.

Next steps

Connect a repository with the quickstart, then check the support matrix on the compatibility page. For other functional codebases, read the Elixir guide.