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Diffstat (limited to 'compiler/parser/Lexer.x')
| -rw-r--r-- | compiler/parser/Lexer.x | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/compiler/parser/Lexer.x b/compiler/parser/Lexer.x index 14a7cb2ffa..6c4abe047a 100644 --- a/compiler/parser/Lexer.x +++ b/compiler/parser/Lexer.x @@ -2797,6 +2797,21 @@ clean_pragma prag = canon_ws (map toLower (unprefix prag)) -- | Encapsulated call to addAnnotation, requiring only the SrcSpan of -- the AST construct the annotation belongs to; together with the -- AnnKeywordId, this is is the key of the annotation map +-- +-- This type is useful for places in the parser where it is not yet +-- known what SrcSpan an annotation should be added to. The most +-- common situation is when we are parsing a list: the annotations +-- need to be associated with the AST element that *contains* the +-- list, not the list itself. 'AddAnn' lets us defer adding the +-- annotations until we finish parsing the list and are now parsing +-- the enclosing element; we then apply the 'AddAnn' to associate +-- the annotations. Another common situation is where a common fragment of +-- the AST has been factored out but there is no separate AST node for +-- this fragment (this occurs in class and data declarations). In this +-- case, the annotation belongs to the parent data declaration. +-- +-- The usual way an 'AddAnn' is created is using the 'mj' ("make jump") +-- function, and then it can be discharged using the 'ams' function. type AddAnn = SrcSpan -> P () addAnnotation :: SrcSpan -- SrcSpan of enclosing AST construct |