syntax for inaccessible patterns in GF

src/compiler/GF/Compile/Abstract/TC.hs

@@ -241,6 +241,7 @@ checkBranch th tenv b@(ps,t) ty = errIn ("branch" +++ show b) $
      PFloat n -> (EFloat n : ps, i, g, k)
      PP m c xs -> (mkApp (Q m c) xss : ps, j, g',k') 
                     where (xss,j,g',k') = foldr p2t ([],i,g,k) xs
+     PTilde t -> (t : ps, i, g, k)
      _ -> error $ render (text "undefined p2t case" <+> ppPatt Unqualified 0 p <+> text "in checkBranch")
 
   upd x k g = (x, VGen k x) : g --- hack to recognize pattern variables

src/compiler/GF/Compile/GrammarToPGF.hs

@@ -145,6 +145,7 @@ mkPatt scope p =
     A.PInt i    -> (  scope,C.PLit (C.LInt (fromIntegral i)))
     A.PFloat f  -> (  scope,C.PLit (C.LFlt f))
     A.PString s -> (  scope,C.PLit (C.LStr s))
+    A.PTilde t  -> (  scope,C.PTilde (mkExp scope t))
 
 
 mkContext :: [Ident] -> A.Context -> ([Ident],[C.Hypo])

src/compiler/GF/Grammar/Binary.hs

@@ -209,6 +209,7 @@ instance Binary Patt where
   put (PChars x)   = putWord8 16 >> put x
   put (PMacro x)   = putWord8 17 >> put x
   put (PM x y)     = putWord8 18 >> put (x,y)
+  put (PTilde x)   = putWord8 19 >> put x
   get = do tag <- getWord8
            case tag of
              0  -> get >>= \(x,y)   -> return (PC x y)
@@ -229,6 +230,7 @@ instance Binary Patt where
              16 -> get >>= \x       -> return (PChars x)
              17 -> get >>= \x       -> return (PMacro x)
              18 -> get >>= \(x,y)   -> return (PM x y)
+             19 -> get >>= \x       -> return (PTilde x)
              _  -> decodingError
 
 instance Binary TInfo where

src/compiler/GF/Grammar/Grammar.hs

@@ -168,6 +168,7 @@ data Patt =
  | PAs Ident Patt         -- ^ as-pattern: x@p
  
  | PImplArg Patt          -- ^ placeholder for pattern for implicit argument @{p}@
+ | PTilde   Term          -- ^ inaccessible pattern
 
  -- regular expression patterns
  | PNeg Patt              -- ^ negated pattern: -p

src/compiler/GF/Grammar/Lexer.x

@@ -23,7 +23,7 @@ $i = [$l $d _ ']          -- identifier character
 $u = [\0-\255]          -- universal: any character
 
 @rsyms =    -- symbols and non-identifier-like reserved words
-   \; | \= | \{ | \} | \( | \) | \* \* | \: | \- \> | \, | \[ | \] | \- | \. | \| | \% | \? | \< | \> | \@ | \# | \! | \* | \+ | \+ \+ | \\ | \\\\ | \= \> | \_ | \$ | \/
+   \; | \= | \{ | \} | \( | \) | \~ | \* \* | \: | \- \> | \, | \[ | \] | \- | \. | \| | \% | \? | \< | \> | \@ | \# | \! | \* | \+ | \+ \+ | \\ | \\\\ | \= \> | \_ | \$ | \/
 
 :-
 "--" [.]* ; -- Toss single line comments
@@ -49,6 +49,7 @@ data Token
  | T_int_label
  | T_oparen
  | T_cparen
+ | T_tilde
  | T_star
  | T_starstar
  | T_plus
@@ -132,6 +133,7 @@ resWords = Map.fromList
  , b "$"  T_int_label
  , b "("  T_oparen
  , b ")"  T_cparen
+ , b "~"  T_tilde
  , b "*"  T_star
  , b "**" T_starstar
  , b "+"  T_plus

src/compiler/GF/Grammar/Parser.y

@@ -35,6 +35,7 @@ import GF.Compile.Update (buildAnyTree)
  '$'          { T_int_label }
  '('          { T_oparen    }
  ')'          { T_cparen    }
+ '~'          { T_tilde     }
  '*'          { T_star      }
  '**'         { T_starstar  }
  '+'          { T_plus      }
@@ -487,6 +488,7 @@ Patt2
   | '[' String ']'            { PChars $2 }
   | '#' Ident                 { PMacro $2 }
   | '#' Ident '.' Ident       { PM $2 $4 }
+  | '~' Exp6                  { PTilde $2 }
   | '_'                       { PW }
   | Ident                     { PV $1 }
   | Ident '.' Ident           { PP $1 $3 [] }
@@ -526,8 +528,8 @@ ListPatt
   | PattArg ListPatt { $1 : $2 }
 
 PattArg :: { Patt }
-  : Patt2         { $1          }
-  | '{' Patt2 '}' { PImplArg $2 }
+  : Patt2         { $1                }
+  | '{' Patt2 '}' { PImplArg $2       }
 
 Arg :: { [(BindType,Ident)] }
 Arg 

src/compiler/GF/Grammar/Printer.hs

@@ -208,6 +208,7 @@ ppPatt q d (PFloat f)   = double f
 ppPatt q d (PString s)  = str s
 ppPatt q d (PR xs)      = braces (hsep (punctuate semi [ppLabel l <+> equals <+> ppPatt q 0 e | (l,e) <- xs]))
 ppPatt q d (PImplArg p) = braces (ppPatt q 0 p)
+ppPatt q d (PTilde t)   = char '~' <> ppTerm q 6 t
 
 ppValue :: TermPrintQual -> Int -> Val -> Doc
 ppValue q d (VGen i x)    = ppIdent x <> text "{-" <> int i <> text "-}" ---- latter part for debugging