remove the Term(Error) constructor. Better propagation of errors.

src/compiler/GF/Grammar/Binary.hs

@@ -189,7 +189,6 @@ instance Binary Term where
   put (FV x)        = putWord8 32 >> put x
   put (Alts x y)    = putWord8 33 >> put (x,y)
   put (Strs x)      = putWord8 34 >> put x
-  put (Error x)     = putWord8 35 >> put x
 
   get = do tag <- getWord8
            case tag of
@@ -228,7 +227,6 @@ instance Binary Term where
              32 -> get >>= \x       -> return (FV x)
              33 -> get >>= \(x,y)   -> return (Alts x y)
              34 -> get >>= \x       -> return (Strs x)
-             35 -> get >>= \x       -> return (Error x)
              _  -> decodingError
 
 instance Binary Patt where

src/compiler/GF/Grammar/Grammar.hs

@@ -398,7 +398,6 @@ data Term =
 
  | Alts Term [(Term, Term)]      -- ^ alternatives by prefix: @pre {t ; s\/c ; ...}@
  | Strs [Term]                   -- ^ conditioning prefix strings: @strs {s ; ...}@
- | Error String                  -- ^ error values returned by Predef.error
   deriving (Show, Eq, Ord)
 
 -- | Patterns

src/compiler/GF/Grammar/Macros.hs

@@ -238,12 +238,6 @@ isPredefConstant t = case t of
   Q (mod,_) | mod == cPredef || mod == cPredefAbs -> True
   _                                               -> False
 
-checkPredefError :: Fail.MonadFail m => Term -> m Term
-checkPredefError t =
-    case t of
-      Error s -> fail ("Error: "++s)
-      _ -> return t
-
 cnPredef :: Ident -> Term
 cnPredef f = Q (cPredef,f)
 

src/compiler/GF/Grammar/Printer.hs

@@ -240,7 +240,6 @@ ppTerm q d (Typed e t) = '<' <> ppTerm q 0 e <+> ':' <+> ppTerm q 0 t <> '>'
 ppTerm q d (ImplArg e) = braces (ppTerm q 0 e)
 ppTerm q d (ELincat cat t) = prec d 4 ("lincat" <+> cat <+> ppTerm q 5 t)
 ppTerm q d (ELin cat t) = prec d 4 ("lin" <+> cat <+> ppTerm q 5 t)
-ppTerm q d (Error s)   = prec d 4 ("Predef.error" <+> str s)
 
 ppEquation q (ps,e) = hcat (map (ppPatt q 2) ps) <+> "->" <+> ppTerm q 0 e