diff options
Diffstat (limited to 'compiler/GHC/Parser/Annotation.hs')
| -rw-r--r-- | compiler/GHC/Parser/Annotation.hs | 36 |
1 files changed, 31 insertions, 5 deletions
diff --git a/compiler/GHC/Parser/Annotation.hs b/compiler/GHC/Parser/Annotation.hs index 1692d394b5..9555291530 100644 --- a/compiler/GHC/Parser/Annotation.hs +++ b/compiler/GHC/Parser/Annotation.hs @@ -100,7 +100,7 @@ import qualified GHC.Data.Strict as Strict {- Note [exact print annotations] -~~~~~~~~~~~~~~~~~~~~~~ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Given a parse tree of a Haskell module, how can we reconstruct the original Haskell source code, retaining all whitespace and source code comments? We need to track the locations of all @@ -394,7 +394,7 @@ instance Outputable EpaComment where -- The usual way an 'AddEpAnn' is created is using the 'mj' ("make -- jump") function, and then it can be inserted into the appropriate -- annotation. -data AddEpAnn = AddEpAnn AnnKeywordId EpaLocation deriving (Data,Eq,Ord) +data AddEpAnn = AddEpAnn AnnKeywordId EpaLocation deriving (Data,Eq) -- | The anchor for an @'AnnKeywordId'@. The Parser inserts the -- @'EpaSpan'@ variant, giving the exact location of the original item @@ -460,6 +460,9 @@ instance Outputable EpaLocation where instance Outputable AddEpAnn where ppr (AddEpAnn kw ss) = text "AddEpAnn" <+> ppr kw <+> ppr ss +instance Ord AddEpAnn where + compare (AddEpAnn kw1 loc1) (AddEpAnn kw2 loc2) = compare (loc1, kw1) (loc2,kw2) + -- --------------------------------------------------------------------- -- | The exact print annotations (EPAs) are kept in the HsSyn AST for @@ -802,7 +805,8 @@ addTrailingAnnToL s t cs EpAnnNotUsed addTrailingAnnToL _ t cs n = n { anns = addTrailing (anns n) , comments = comments n <> cs } where - addTrailing n = n { al_trailing = t : al_trailing n } + -- See Note [list append in addTrailing*] + addTrailing n = n { al_trailing = al_trailing n ++ [t]} -- | Helper function used in the parser to add a 'TrailingAnn' items -- to an existing annotation. @@ -813,7 +817,8 @@ addTrailingAnnToA s t cs EpAnnNotUsed addTrailingAnnToA _ t cs n = n { anns = addTrailing (anns n) , comments = comments n <> cs } where - addTrailing n = n { lann_trailing = t : lann_trailing n } + -- See Note [list append in addTrailing*] + addTrailing n = n { lann_trailing = lann_trailing n ++ [t] } -- | Helper function used in the parser to add a comma location to an -- existing annotation. @@ -822,8 +827,29 @@ addTrailingCommaToN s EpAnnNotUsed l = EpAnn (spanAsAnchor s) (NameAnnTrailing [AddCommaAnn l]) emptyComments addTrailingCommaToN _ n l = n { anns = addTrailing (anns n) l } where + -- See Note [list append in addTrailing*] addTrailing :: NameAnn -> EpaLocation -> NameAnn - addTrailing n l = n { nann_trailing = AddCommaAnn l : nann_trailing n } + addTrailing n l = n { nann_trailing = nann_trailing n ++ [AddCommaAnn l]} + +{- +Note [list append in addTrailing*] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The addTrailingAnnToL, addTrailingAnnToA and addTrailingCommaToN +functions are used to add a separator for an item when it occurs in a +list. So they are used to capture a comma, vbar, semicolon and similar. + +In general, a given element will have zero or one of these. In +extreme (test) cases, there may be multiple semicolons. + +In exact printing we sometimes convert the EpaLocation variant for an +trailing annotation to the EpaDelta variant, which cannot be sorted. + +Hence it is critical that these annotations are captured in the order +they appear in the original source file. + +And so we use the less efficient list append to preserve the order, +knowing that in most cases the original list is empty. +-} -- --------------------------------------------------------------------- |