Current formatting rules in this project

Data declarations

• One liner: data A = A. For data types with one constructor, if it does not exceeds the maximum line length, it is OK.
• First break at the equals sign, ident the equals sign to two spaces.
• Multiple constructors: Break before the |. Ident the | at two spaces.
• Parameters: If need to break align the last one on two spaces right to the constructor name.
• Records: Align every start of record to the same column.
  • One liner: data A = A { x :: Int } If there are only one field
  • Align the comma on the start of the record.

data Expr dom stage
  = Var      { exprName :: Ann Name dom stage 
             } -- ^ A variable or a data constructor (@ a @)
  | Lit      { exprLit :: Ann Literal dom stage }
  | InfixApp { exprLhs :: Ann Expr dom stage
             , exprOperator :: Ann Operator dom stage
             , exprRhs :: Ann Expr dom stage
             }

Type signatures

• Break where we gain the most room.
• When breaking on the context, align the context in line with the :: sign.
• When breaking on operator (including ->) follow the rules of breaking on operators and align it to two spaces relative to the type.

Expressions

• Break according to precedence. First break the lower-precedence operators. Then the higher precedence operator, after that, break on normal function application.
• When breaking on the same precedence break from right to left.
• Can always break on the = sign, if this gives more room.
• After a break align the next row to two spaces from the start of the expression.

Some reading: haskell-style-guide