From 3ef786673ff8298124cd3b5ef50c35dbb23f77e2 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Tue, 13 Feb 2024 22:51:57 +0100
Subject: Parse basic ADTs, and fix bugs

---
 Parser.hs | 120 ++++++++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 81 insertions(+), 39 deletions(-)

(limited to 'Parser.hs')

diff --git a/Parser.hs b/Parser.hs
index b31ffa1..0f0bd0c 100644
--- a/Parser.hs
+++ b/Parser.hs
@@ -25,11 +25,12 @@ import Control.Monad.Reader
 import Control.Monad.State.Lazy
 import Data.Bifunctor (first)
 import Data.Char
+import Data.Either (partitionEithers)
 import Data.List.NonEmpty (NonEmpty(..))
 import Data.These
 import Data.Tuple (swap)
 
-import Debug.Trace
+-- import Debug.Trace
 
 import AST
 
@@ -80,7 +81,7 @@ instance Monad Parser where
                                These errs' res -> These (errs <> errs') res
 
 instance Alternative Parser where
-  empty = Parser (\_ _ -> This mempty)
+  empty = Parser (\_ _ -> This [])
   Parser f <|> Parser g = Parser $ \ctx ps ->
     case f ctx ps of
       This _ -> g ctx ps
@@ -128,15 +129,35 @@ parse fp source = fmap snd $ runParser pProgram (Context fp []) (PS 0 0 0 0 sour
 
 pProgram :: Parser (Program ())
 pProgram = do
-  prog <- Program <$> many pFunDef
+  defs <- many pTopDef
+  let (datadefs, fundefs) = partitionEithers defs
   skipWhiteComment
   assertEOF Error
-  return prog
+  return (Program datadefs fundefs)
 
-pFunDef :: Parser (FunDef ())
-pFunDef = do
+pTopDef :: Parser (Either DataDef (FunDef ()))
+pTopDef = do
   skipWhiteComment
-  pFunDef0
+  Left <$> pDataDef0 <|> Right <$> pFunDef0
+
+pDataDef0 :: Parser DataDef
+pDataDef0 = do
+  pKeyword "data"
+  inlineWhite
+  name <- pIdentifier0 InBlock Uppercase
+  params <- many (inlineWhite >> pIdentifier0 InBlock Lowercase)
+  cons <- pDatacons "="
+  return (DataDef name params cons)
+  where
+    pDatacons :: String -> Parser [(Name, [Type])]
+    pDatacons leader = do
+      inlineWhite
+      pKeySym leader
+      inlineWhite
+      name <- pIdentifier0 InBlock Uppercase
+      fields <- many pTypeAtom
+      rest <- pDatacons "|" <|> return []
+      return ((name, fields) : rest)
 
 pFunDef0 :: Parser (FunDef ())
 pFunDef0 = do
@@ -430,12 +451,12 @@ pType = do
 
 pTypeApp :: Parser Type
 pTypeApp = many pTypeAtom >>= \case
-  [] -> raise Error "Expected type" >> return (TTup [])
+  [] -> raise Fatal "Expected type"
   [t] -> return t
   t:ts -> return (TApp t ts)
 
 pTypeAtom :: Parser Type
-pTypeAtom = pTypeParens <|> pTypeList <|> pTypeCon <|> pTypeVar
+pTypeAtom = pTypeParens <|> pTypeList <|> pTypeName
   where
     pTypeParens = do
       inlineWhite
@@ -461,8 +482,12 @@ pTypeAtom = pTypeParens <|> pTypeList <|> pTypeCon <|> pTypeVar
       char ']'
       return (TList ty)
 
-    pTypeCon = inlineWhite >> TCon <$> pIdentifier0 InBlock Uppercase
-    pTypeVar = inlineWhite >> TVar <$> pIdentifier0 InBlock Lowercase
+    pTypeName = do
+      inlineWhite
+      (cs, name) <- pIdentifier0 InBlock Don'tCare
+      case cs of
+        Uppercase -> return (TCon name)
+        Lowercase -> return (TVar name)
 
 -- | Parse the given name-like keyword, ensuring that it is the entire word.
 pKeyword :: String -> Parser ()
@@ -476,13 +501,20 @@ pKeySym s = do
   string s
   notFollowedBy (() <$ satisfy isSymbolChar)
 
-data Case = Uppercase | Lowercase
-  deriving (Show)
+data Case care where
+  Uppercase :: Case 'True
+  Lowercase :: Case 'True
+  Don'tCare :: Case 'False
+deriving instance Show (Case care)
+
+type family WithCaseOutput care a where
+  WithCaseOutput 'True a = a
+  WithCaseOutput 'False a = (Case 'True, a)
 
 -- | Consumes an identifier (word or parenthesised operator) at the current
 -- position. The `var` production in Haskell2010.
 -- var -> varid | "(" varsym ")"
-pIdentifier0 :: BlockPos -> Case -> Parser Name
+pIdentifier0 :: BlockPos -> Case care -> Parser (WithCaseOutput care Name)
 pIdentifier0 bpos cs = pAlphaName0 bpos cs <|> pParens0 (pSymbol0 bpos cs)
   where
     -- | Parser between parens, with the opening paren at the current position.
@@ -499,7 +531,7 @@ pIdentifier0 bpos cs = pAlphaName0 bpos cs <|> pParens0 (pSymbol0 bpos cs)
 -- `varid` production in Haskell2010 for 'Lowercase', `conid' for 'Uppercase'.
 --
 -- > varid -> (small {small | large | digit | "'"}) without reservedid
-pAlphaName0 :: BlockPos -> Case -> Parser Name
+pAlphaName0 :: BlockPos -> Case care -> Parser (WithCaseOutput care Name)
 pAlphaName0 bpos cs = do
   (_, s) <- readToken
       bpos
@@ -509,19 +541,25 @@ pAlphaName0 bpos cs = do
           (False, Just c) | isNameContChar c -> Just (Right False)
           (False, _     )                    -> Just (Left ()))
       True
-  name <- case cs of
-    Uppercase | isLower (head s) -> do
-        raise Error "Unexpected uppercase word at this position, assuming typo"
-        return (toUpper (head s) : tail s)
-    Lowercase | isUpper (head s) -> do
-        raise Error "Unexpected lowercase word at this position, assuming typo"
-        return (toLower (head s) : tail s)
-    _ -> return s
+  (name, adjoin) <- case cs of
+    Uppercase
+      | isLower (head s) -> do
+          raise Error "Unexpected uppercase word at this position, assuming typo"
+          return (toUpper (head s) : tail s, id)
+      | otherwise -> return (s, id)
+    Lowercase
+      | isUpper (head s) -> do
+          raise Error "Unexpected lowercase word at this position, assuming typo"
+          return (toLower (head s) : tail s, id)
+      | otherwise -> return (s, id)
+    Don'tCare
+      | isLower (head s) -> return (s, (Lowercase,))
+      | otherwise        -> return (s, (Lowercase,))
   guard (name `notElem` ["case", "class", "data", "default", "deriving", "do", "else"
                         ,"foreign", "if", "import", "in", "infix", "infixl"
                         ,"infixr", "instance", "let", "module", "newtype", "of"
                         ,"then", "type", "where", "_"])
-  return (Name name)
+  return (adjoin (Name name))
 
 isNameHeadChar :: Char -> Bool
 isNameHeadChar c = isLetter c || c == '_'
@@ -530,7 +568,7 @@ isNameContChar :: Char -> Bool
 isNameContChar c = isNameHeadChar c || isDigit c || c == '\''
 
 -- | Consumes a symbol at the current position. The `varsym` production in
--- Haskell2010 for 'Lowercase', `consym` otherwise.
+-- Haskell2010 for 'Lowercase', `consym` otherwise, and either if 'Don'tCare'.
 --
 -- > varsym -> ((symbol without ":") {symbol}) without (reservedop | dashes)
 -- > consym -> (":" {symbol}) without reservedop
@@ -540,24 +578,28 @@ isNameContChar c = isNameHeadChar c || isDigit c || c == '\''
 -- > dashes -> "--" {"-"}
 -- > special -> ```(),;[]`{}```
 -- > reservedop -> ".." | ":" | "::" | "=" | "\" | "|" | "<-" | "->" | "@" | "~" | "=>"
-pSymbol0 :: BlockPos -> Case -> Parser Name
+pSymbol0 :: BlockPos -> Case care -> Parser (WithCaseOutput care Name)
 pSymbol0 bpos cs = do
   case bpos of
     AtLeft -> assertAtBlockLeft Fatal "Expected symbol, but found indented expression"
     InBlock -> assertInsideBlock Fatal "Expected symbol, but found end of indented expression"
-  name <- (:) <$> (case cs of Lowercase -> satisfy (\c -> isSymbolChar c && c /= ':')
-                              Uppercase -> satisfy (== ':'))
-              <*> many (satisfy isSymbolChar)
+  (c1, adjoin) <-
+    case cs of Lowercase -> (,id) <$> satisfy (\c -> isSymbolChar c && c /= ':')
+               Uppercase -> (,id) <$> satisfy (== ':')
+               Don'tCare -> do c1 <- satisfy (\c -> isSymbolChar c)
+                               return (c1, if c1 == ':' then (Uppercase,) else (Lowercase,))
+  crest <- many (satisfy isSymbolChar)
+  let name = c1 : crest
   guard (name `notElem` ["..", ":", "::", "=", "\\", "|", "<-", "->", "@", "~", "=>"])
   guard (take 2 name /= "--")
-  return (Name name)
+  return (adjoin (Name name))
 
 isSymbolChar :: Char -> Bool
 isSymbolChar c = (isAscSymbol || isUniSymbol) && not isSpecialExt
   where
     isSpecialExt = c `elem` "(),;[]`{}_\"'"
     isAscSymbol = c `elem` "!#$%&⋆+./<=>?@^|-~:"
-    isUniSymbol = isSymbol c || isPunctuation c
+    isUniSymbol = ord c > 127 && (isSymbol c || isPunctuation c)
 
 
 sepBy1 :: Parser a -> Parser sep -> Parser [a]
@@ -650,10 +692,10 @@ skipWhiteComment = do
   _ <- many (blockComment >> inlineSpaces)
   optional_ lineComment
   optional_ (consumeNewline >> skipWhiteComment)
-
--- | Consumes some inline whitespace. Stops before newlines.
-inlineSpaces :: Parser ()
-inlineSpaces = readWhileInline isSpace
+  where
+    -- | Consumes some inline whitespace. Stops before newlines.
+    inlineSpaces :: Parser ()
+    inlineSpaces = readWhileInline isSpace
 
 -- | Consumes an delimited comment including both end markers. Note: this may
 -- end outside the current block.
@@ -724,12 +766,12 @@ consumeNewline = gets psRest >>= \case
 -- | Consumes exactly one character, unequal to newline, at the current position.
 satisfy :: (Char -> Bool) -> Parser Char
 satisfy p = do
-  traceM "entering satisfy"
+  -- traceM "entering satisfy"
   r <- gets psRest
-  traceM "got rest"
+  -- traceM "got rest"
   r `seq` return ()
-  traceM "seqd rest"
-  traceM ("rest is " ++ show r)
+  -- traceM "seqd rest"
+  -- traceM ("rest is " ++ show r)
   case r of
     c : rest | c /= '\n', p c -> do
         modify (\ps -> ps { psCol = psCol ps + 1
-- 
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