Do not use Prelude; concoct our own Happy_Prelude alias (#325)

This is in order to undo a breaking change caused by users
writing `import Prelude hiding (null)`.

Fixes #325.

ChangeLog.md

@@ -1,5 +1,10 @@
 # Revision history for Happy
 
+## 2.1.2
+
+Fix a breaking change (#325) introduced by the previous fix for #131.
+Prelude is no longer used by Happy.
+
 ## 2.1.1
 
 This release fixes two breaking changes:

doc/syntax.rst

@@ -66,9 +66,6 @@ This section is optional, but if included takes the following form:
 
 The Haskell module header contains the module name, exports, and imports.
 No other code is allowed in the header—this is because Happy may need to include its own ``import`` statements directly after the user defined header.
-Do note that Happy relies on ``Prelude`` from ``base`` being in scope qualified.
-Users who hide functions from ``Prelude`` or redefine it to use a custom prelude
-must also ``import qualified "base" Prelude`` for Happy.
 
 .. _sec-directives:
 

happy.cabal

@@ -1,5 +1,5 @@
 name: happy
-version: 2.1.1
+version: 2.1.2
 license: BSD2
 license-file: LICENSE
 copyright: (c) Andy Gill, Simon Marlow

lib/backend-lalr/src/Happy/Backend/LALR.hs

@@ -19,16 +19,16 @@ magicFilter magicName = case magicName of
       in filter_output
 
 importsToInject :: Bool -> String
-importsToInject debug = concat ["\n", import_array, import_list, import_bits, import_glaexts, debug_imports, applicative_imports]
+importsToInject debug = concat ["\n", import_prelude, import_array, import_bits, import_glaexts, debug_imports, applicative_imports]
     where
       debug_imports  | debug     = import_debug
                      | otherwise = ""
       applicative_imports        = import_applicative
 
       import_glaexts     = "import qualified GHC.Exts as Happy_GHC_Exts\n"
       _import_ghcstack   = "import qualified GHC.Stack as Happy_GHC_Stack\n"
+      import_prelude     = "import qualified Data.Bool as Happy_Prelude\nimport qualified Data.Function as Happy_Prelude\nimport qualified Data.Maybe as Happy_Prelude\nimport qualified Data.Int as Happy_Prelude\nimport qualified Data.String as Happy_Prelude\nimport qualified Data.List as Happy_Prelude\nimport qualified Control.Monad as Happy_Prelude\nimport qualified Text.Show as Happy_Prelude\nimport qualified GHC.Num as Happy_Prelude\nimport qualified GHC.Err as Happy_Prelude\n"
       import_array       = "import qualified Data.Array as Happy_Data_Array\n"
-      import_list        = "import qualified Data.List as Happy_Data_List\n"
       import_bits        = "import qualified Data.Bits as Bits\n"
       import_debug       = "import qualified System.IO as Happy_System_IO\n" ++
                            "import qualified System.IO.Unsafe as Happy_System_IO_Unsafe\n" ++

lib/backend-lalr/src/Happy/Backend/LALR/ProduceCode.lhs

@@ -218,7 +218,7 @@ example where this matters.
 >     | otherwise
 >       = str "data HappyAbsSyn " . str_tyvars
 >       . str "\n" . indent . str "= HappyTerminal " . token
->       . str "\n" . indent . str "| HappyErrorToken Prelude.Int\n"
+>       . str "\n" . indent . str "| HappyErrorToken Happy_Prelude.Int\n"
 >       . interleave "\n"
 >         [ str "" . indent . str "| " . makeAbsSynCon n . strspace . typeParam n ty
 >         | (n, ty) <- assocs nt_types,
@@ -381,7 +381,7 @@ The token conversion function.
 >             . str "\\i tk -> " . doAction . str " sts stk)\n"
 >       . str "\n"
 >       . str "happyReport " . eofTok . str " tk explist resume tks = happyReport' tks explist resume\n"
->       . str "happyReport _ tk explist resume tks = happyReport' (tk:tks) explist (\\tks -> resume (Prelude.tail tks))\n"
+>       . str "happyReport _ tk explist resume tks = happyReport' (tk:tks) explist (\\tks -> resume (Happy_Prelude.tail tks))\n"
 >             -- when the token is EOF, tk == _|_ (notHappyAtAll)
 >             -- so we must not pass it to happyReport'
 >       . str "\n";
@@ -488,9 +488,9 @@ machinery to discard states in the parser...
 >       . produceReduceArray
 >       . produceRuleArray
 >       . produceCatchStates
->       . str "happy_n_terms = " . shows n_terminals . str " :: Prelude.Int\n"
->       . str "happy_n_nonterms = " . shows n_nonterminals . str " :: Prelude.Int\n\n"
->       . str "happy_n_starts = " . shows n_starts . str " :: Prelude.Int\n\n"
+>       . str "happy_n_terms = " . shows n_terminals . str " :: Happy_Prelude.Int\n"
+>       . str "happy_n_nonterms = " . shows n_nonterminals . str " :: Happy_Prelude.Int\n\n"
+>       . str "happy_n_starts = " . shows n_starts . str " :: Happy_Prelude.Int\n\n"
 >
 >    produceTokToStringList
 >       = str "{-# NOINLINE happyTokenStrings #-}\n"
@@ -553,7 +553,7 @@ action array indexed by (terminal * last_state) + state
 >    n_rules = length prods - 1 :: Int
 >
 >    produceCatchStates
->       = str "happyCatchStates :: [Prelude.Int]\n"
+>       = str "happyCatchStates :: [Happy_Prelude.Int]\n"
 >       . str "happyCatchStates = " . shows catch_states . str "\n\n"
 
 >    showInt i = shows i . showChar '#'
@@ -599,12 +599,12 @@ outlaw them inside { }
 >            str "newtype HappyIdentity a = HappyIdentity a\n"
 >          . str "happyIdentity = HappyIdentity\n"
 >          . str "happyRunIdentity (HappyIdentity a) = a\n\n"
->          . str "instance Prelude.Functor HappyIdentity where\n"
+>          . str "instance Happy_Prelude.Functor HappyIdentity where\n"
 >          . str "    fmap f (HappyIdentity a) = HappyIdentity (f a)\n\n"
 >          . str "instance Applicative HappyIdentity where\n"
 >          . str "    pure  = HappyIdentity\n"
 >          . str "    (<*>) = ap\n"
->          . str "instance Prelude.Monad HappyIdentity where\n"
+>          . str "instance Happy_Prelude.Monad HappyIdentity where\n"
 >          . str "    return = pure\n"
 >          . str "    (HappyIdentity p) >>= q = q p\n\n"
 
@@ -652,7 +652,7 @@ MonadStuff:
 >                . str " a\n"
 >                . str "happyReport' :: " . pcont . str " => "
 >                . str "[" . token . str "] -> "
->                . str "[Prelude.String] -> ("
+>                . str "[Happy_Prelude.String] -> ("
 >                . str "[" . token . str "] -> "
 >                . ptyAt (str "a") . str ") -> "
 >                . ptyAt (str "a")
@@ -684,7 +684,7 @@ MonadStuff:
 >                      . str "\n"
 >                  reduceArrSig =
 >                        str "happyReduceArr :: " . pcont
->                      . str " => Happy_Data_Array.Array Prelude.Int (" . intMaybeHash
+>                      . str " => Happy_Data_Array.Array Happy_Prelude.Int (" . intMaybeHash
 >                      . str " -> " . str token_type' . str " -> " . intMaybeHash
 >                      . str " -> Happy_IntList -> HappyStk " . happyAbsSyn
 >                      . str " -> " . ptyAt happyAbsSyn . str ")\n"
@@ -699,7 +699,7 @@ MonadStuff:
 >                . str "happyReturn1 = happyReturn\n"
 >                . str "happyReport' :: " . pcont . str " => "
 >                . token . str " -> "
->                . str "[Prelude.String] -> "
+>                . str "[Happy_Prelude.String] -> "
 >                . ptyAt (str "a") . str " -> "
 >                . ptyAt (str "a")
 >                . str "\n"
@@ -726,7 +726,7 @@ have a special code path for `OldExpected`.
 >    callReportError = -- this one wraps around report_error_handler to expose a unified interface
 >       str "(\\tokens expected resume -> " .
 >       (if use_monad then str ""
->                     else str "HappyIdentity Prelude.$ ") .
+>                     else str "HappyIdentity Happy_Prelude.$ ") .
 >       report_error_handler .
 >       (case error_expected' of
 >          OldExpected -> str " (tokens, expected)"  -- back-compat for %errorhandlertype
@@ -744,7 +744,7 @@ have a special code path for `OldExpected`.
 >       ResumptiveErrorHandler _abort report -> brack report
 >    abort_handler = case error_handler' of
 >       ResumptiveErrorHandler abort _report -> abort
->       _                                    -> "Prelude.error \"Called abort handler in non-resumptive parser\""
+>       _                                    -> "Happy_Prelude.error \"Called abort handler in non-resumptive parser\""
 
 >    reduceArrElem n
 >      = str "" . indent . str "(" . shows n . str " , "
@@ -799,21 +799,21 @@ have a special code path for `OldExpected`.
 >         . str "do { "
 >         . str "f <- do_" . str name . str "; "
 >         . str "let { (conds,attrs) = f happyEmptyAttrs } in do { "
->         . str "Prelude.sequence_ conds; "
->         . str "Prelude.return (". str defaultAttr . str " attrs) }}"
+>         . str "Happy_Prelude.sequence_ conds; "
+>         . str "Happy_Prelude.return (". str defaultAttr . str " attrs) }}"
 >       monadAE name
 >         = str name . str " toks = "
 >         . str "do { "
 >         . str "f <- do_" . str name . str " toks; "
 >         . str "let { (conds,attrs) = f happyEmptyAttrs } in do { "
->         . str "Prelude.sequence_ conds; "
->         . str "Prelude.return (". str defaultAttr . str " attrs) }}"
+>         . str "Happy_Prelude.sequence_ conds; "
+>         . str "Happy_Prelude.return (". str defaultAttr . str " attrs) }}"
 >       regularAE name
 >         = str name . str " toks = "
 >         . str "let { "
 >         . str "f = do_" . str name . str " toks; "
 >         . str "(conds,attrs) = f happyEmptyAttrs; "
->         . str "x = Prelude.foldr Prelude.seq attrs conds; "
+>         . str "x = Happy_Prelude.foldr Happy_GHC_Exts.seq attrs conds; "
 >         . str "} in (". str defaultAttr . str " x)"
 
 ----------------------------------------------------------------------------
@@ -830,7 +830,7 @@ have a special code path for `OldExpected`.
 >   where attributes'  = foldl1 (\x y -> x . str ", " . y) $ map formatAttribute attrs
 >         formatAttribute (ident,typ) = str ident . str " :: " . str typ
 >         attrsErrors = foldl1 (\x y -> x . str ", " . y) $ map attrError attrs
->         attrError (ident,_) = str ident . str " = Prelude.error \"invalid reference to attribute '" . str ident . str "'\""
+>         attrError (ident,_) = str ident . str " = Happy_Prelude.error \"invalid reference to attribute '" . str ident . str "'\""
 >         attrHeader =
 >             case attributeType of
 >             [] -> str "HappyAttributes"