ghc-exactprint- ExactPrint for GHC

Safe HaskellNone




Core Types

type Anns = Map AnnKey Annotation Source

This structure holds a complete set of annotations for an AST

data Annotation Source




annEntryDelta :: !DeltaPos

Offset used to get to the start of the SrcSpan, from whatever the prior output was, including all annPriorComments (field below).

annPriorComments :: ![(Comment, DeltaPos)]

Comments coming after the last non-comment output of the preceding element but before the SrcSpan being annotated by this Annotation. If these are changed then annEntryDelta (field above) must also change to match.

annFollowingComments :: ![(Comment, DeltaPos)]

Comments coming after the last output for the element subject to this Annotation. These will only be added by AST transformations, and care must be taken not to disturb layout of following elements.

annsDP :: ![(KeywordId, DeltaPos)]

Annotations associated with this element.

annSortKey :: !(Maybe [SrcSpan])

Captures the sort order of sub elements. This is needed when the sub-elements have been split (as in a HsLocalBind which holds separate binds and sigs) or for infix patterns where the order has been re-arranged. It is captured explicitly so that after the Delta phase a SrcSpan is used purely as an index into the annotations, allowing transformations of the AST including the introduction of new Located items or re-arranging existing ones.

annCapturedSpan :: !(Maybe AnnKey)

Occasionally we must calculate a SrcSpan for an unlocated list of elements which we must remember for the Print phase. e.g. the statements in a HsLet or HsDo. These must be managed as a group because they all need eo be vertically aligned for the Haskell layout rules, and this guarantees this property in the presence of AST edits.

data KeywordId Source

The different syntactic elements which are not represented in the AST.


G AnnKeywordId

A normal keyword


A seperating comma

AnnComment Comment 
AnnString String

Used to pass information from Delta to Print when we have to work out details from the original SrcSpan.

AnnUnicode AnnKeywordId

Used to indicate that we should print using unicode syntax if possible.

data Comment Source

A Haskell comment. The AnnKeywordId is present if it has been converted from an AnnKeywordId because the annotation must be interleaved into the stream and does not have a well-defined position




commentContents :: !String

The contents of the comment including separators

commentIdentifier :: !SrcSpan

Needed to uniquely identify two comments with the same contents

commentOrigin :: !(Maybe AnnKeywordId)

We sometimes turn syntax into comments in order to process them properly.


type Pos = (Int, Int) Source

newtype DeltaPos Source

A relative positions, row then column


DP (Int, Int) 


data AnnKey Source

For every Located a, use the SrcSpan and constructor name of a as the key, to store the standard annotation. These are used to maintain context in the AP and EP monads


AnnKey SrcSpan AnnConName 

mkAnnKey :: Data a => Located a -> AnnKey Source

Make an unwrapped AnnKey for the LHsDecl case, a normal one otherwise.


Internal Types

newtype LayoutStartCol Source

Marks the start column of a layout block.



declFun :: (forall a. Data a => Located a -> b) -> LHsDecl RdrName -> b Source