Fix DITemplateTypeParameter and DITemplateValueParameter

Tested and working on a _very_ large C++ program.

Fixes #43, text copied from that issue:

--------------------------------------------------------

Okay, this particular node has an especially twisted history.

 0. [Feb 12, 2015](llvm-mirror/llvm@8921bbc): `MDTemplateTypeParameter` lands. It's fields have type
    i. `Num`
   ii. `Maybe PValMd`
   iii. `MDString`
   iv. `Maybe PValMd`
    v. `Maybe PValMd`
 1. [Feb 18, 2015](llvm-mirror/llvm@eac950e ): The last field, "scope", was dropped, and the type of the second field was made into a `MDString`.
 2. [Apr 23, 2016](llvm-mirror/llvm@de74840): Removal of MDString-based references (see #39). Third field is made into a `DITypeRef`.

Interestingly, at no point in this process does the field only have three fields, [as it does in the AST](https://github.com/elliottt/llvm-pretty/blob/de881be8e97bc085150d816d359599d75ad3ac9b/src/Text/LLVM/AST.hs#L1100).

The biggest flaw I'm seeing is that the first field of the record _is not a reference_, but it is looked up as if it is one. This is causing the parser to crash, because the reference is not defined.

src/Text/LLVM/AST.hs

@@ -1092,14 +1092,15 @@ data DIImportedEntity' lab = DIImportedEntity
 
 type DITemplateTypeParameter = DITemplateTypeParameter' BlockLabel
 data DITemplateTypeParameter' lab = DITemplateTypeParameter
- { dittpName :: String
- , dittpType :: ValMd' lab
+ { dittpName :: Maybe String
+ , dittpType :: Maybe (ValMd' lab)
  } deriving (Data, Eq, Functor, Generic, Generic1, Ord, Show, Typeable)
 
 type DITemplateValueParameter = DITemplateValueParameter' BlockLabel
 data DITemplateValueParameter' lab = DITemplateValueParameter
- { ditvpName :: String
- , ditvpType :: ValMd' lab
+ { ditvpTag :: DwarfTag
+ , ditvpName :: Maybe String
+ , ditvpType :: Maybe (ValMd' lab)
  , ditvpValue :: ValMd' lab
  } deriving (Data, Eq, Functor, Generic, Generic1, Ord, Show, Typeable)
 

src/Text/LLVM/PP.hs

@@ -867,19 +867,20 @@ ppDINameSpace = ppDINameSpace' ppLabel
 
 ppDITemplateTypeParameter' :: LLVM => (i -> Doc) -> DITemplateTypeParameter' i -> Doc
 ppDITemplateTypeParameter' pp tp = "!DITemplateTypeParameter"
- <> parens (commas [ "name:" <+> text (dittpName tp)
- , "type:" <+> ppValMd' pp (dittpType tp)
- ])
+ <> parens (mcommas [ ("name:"  <+>) . text  <$> dittpName tp
+  , ("type:"  <+>) . ppValMd' pp <$> dittpType tp
+  ])
 
 ppDITemplateTypeParameter :: LLVM => DITemplateTypeParameter -> Doc
 ppDITemplateTypeParameter = ppDITemplateTypeParameter' ppLabel
 
 ppDITemplateValueParameter' :: LLVM => (i -> Doc) -> DITemplateValueParameter' i -> Doc
 ppDITemplateValueParameter' pp vp = "!DITemplateValueParameter"
- <> parens (commas [ "name:" <+> text (ditvpName vp)
- , "type:" <+> ppValMd' pp (ditvpType vp)
- , "value:" <+> ppValMd' pp (ditvpValue vp)
- ])
+ <> parens (mcommas [ pure ("tag:" <+> integral (ditvpTag vp))
+ , ("name:" <+>) . text <$> ditvpName vp
+ , ("type:" <+>) . ppValMd' pp <$> ditvpType vp
+ , pure ("value:" <+> ppValMd' pp (ditvpValue vp))
+ ])
 
 ppDITemplateValueParameter :: LLVM => DITemplateValueParameter -> Doc
 ppDITemplateValueParameter = ppDITemplateValueParameter' ppLabel