support simple interval literal interval '3 days' and rename CastOp to TypedLit

Language/SQL/SimpleSQL/Fixity.lhs

@@ -107,7 +107,7 @@ the fixity code.
 >                               ,HSE.List $ map (ltoh . (\(a,b) -> [a,b])) ts
 >                               ,ltoh $ maybeToList el])
 >     Cast e0 tn -> HSE.App (str ('c':show tn)) $ toHaskell e0
->     CastOp {} -> str ('v':show e)
+>     TypedLit {} -> str ('v':show e)
 >     SubQueryExpr {} -> str ('v': show e)
 >     In b e0 (InList l) ->
 >         HSE.App (str ('i':show b))

Language/SQL/SimpleSQL/Parser.lhs

@@ -99,12 +99,16 @@ interval '5' day (3)
 or
 interval '5' month
 
+wrap the whole lot in try, in case we get something like this:
+interval '3 days'
+which parses as a typed literal
+
 > interval :: P ScalarExpr
-> interval = try (keyword_ "interval") >>
+> interval = try (keyword_ "interval" >>
 >     IntervalLit
 >     <$> stringLiteral
 >     <*> identifierString
->     <*> optionMaybe (try $ parens integerLiteral)
+>     <*> optionMaybe (try $ parens integerLiteral))
 
 > literal :: P ScalarExpr
 > literal = number <|> estring <|> interval
@@ -210,7 +214,7 @@ cast: cast(expr as type)
 >     parensCast = try (keyword_ "cast") >>
 >                  parens (Cast <$> scalarExpr'
 >                          <*> (keyword_ "as" *> typeName))
->     prefixCast = try (CastOp <$> typeName
+>     prefixCast = try (TypedLit <$> typeName
 >                              <*> stringLiteral)
 
 extract(id from expr)

Language/SQL/SimpleSQL/Pretty.lhs

@@ -111,7 +111,7 @@
 >                                ,text "as"
 >                                ,text tn])
 
-> scalarExpr (CastOp (TypeName tn) s) =
+> scalarExpr (TypedLit (TypeName tn) s) =
 >     text tn <+> quotes (text s)
 
 > scalarExpr (SubQueryExpr ty qe) =

Language/SQL/SimpleSQL/Syntax.lhs

@@ -88,7 +88,7 @@
 >       -- | cast(a as typename)
 >     | Cast ScalarExpr TypeName
 >       -- | prefix 'typed literal', e.g. int '42'
->     | CastOp TypeName String
+>     | TypedLit TypeName String
 >       -- | exists, all, any, some subqueries
 >     | SubQueryExpr SubQueryExprType QueryExpr
 >       -- | in list literal and in subquery, if the bool is false it