unrelated instances of a single class are shown along with a data type definition

[imz]

Near the definition of NodeInfo, unrelated instances of a single class Pretty for other data types (not NodeInfo) at https://hackage.haskell.org/package/language-c-0.4.7/docs/Language-C-Data-Node.html#t:NodeInfo (Produced by Haddock version 2.15.0):

data NodeInfo
Source

Parsed entity attribute

Constructors
OnlyPos Position !PosLength  
NodeInfo Position !PosLength !Name   

Instances
Eq NodeInfo  
Data NodeInfo    
Ord NodeInfo     
Show NodeInfo    
Pos NodeInfo     
CNode NodeInfo   
Pretty CStrLit   
Pretty CConst    
Pretty CBuiltin  
Pretty CExpr     
Pretty CAttr     
Pretty CDesignator   
Pretty CInit     
Pretty CEnum     
Pretty CStructUnion  
Pretty CTypeQual     
Pretty CTypeSpec     
Pretty CStorageSpec  
Pretty CDeclSpec     
Pretty CBlockItem    
Pretty CAsmOperand   
Pretty CAsmStmt  
Pretty CStat     
Pretty CArrSize  
Pretty CDeclr    
Pretty CDecl     
Pretty CFunDef   
Pretty CExtDecl  
Pretty CTranslUnit   
Typeable * NodeInfo  

[harpocrates]

These instances are actually not unrelated to NodeInfo. Haddock displays all instances where the type being documented is mentioned in the instance head. Notice that CStrLit, CConst, ... , CTranslUnit all are type synonyms:

-- from Language.C.AST
type CStrLit = CStringLiteral NodeInfo
type CConst = CConstant NodeInfo
...
type CTranslUnit = CTranslationUnit NodeInfo

So the questionable Pretty instances are actually flexible instances that do involved NodeInfo.

-- the instances are _equivalent_ to
instance Pretty (CStringLiteral NodeInfo) where ...
instance Pretty (CConstant NodeInfo) where ...
...
instance Pretty (CTranslUnit NodeInfo) where ...

I'm not sure what the best way is to deal with all of this. If anyone has a suggestion for how to make this clearer, please do tell.