Rework module system

Don't require/allow naming a module, instead require that the importer
names it. Allow importing into the local scope with the name !Local.
Simplify namespacing logic. Updates all tests to reflect these changes.

src/Lexer.hs

@@ -12,39 +12,71 @@ import qualified Data.Set as Set
 
 type Lexer = Parsec Void String
 
+tricuLexer :: Lexer [LToken]
+tricuLexer = do
+  sc
+  header <- many $ do
+    tok <- choice
+      [ try lImport
+      , lnewline
+      ]
+    sc
+    pure tok
+  tokens <- many $ do
+    tok <- choice tricuLexer'
+    sc
+    pure tok
+  sc
+  eof
+  pure (header ++ tokens)
+  where
+    tricuLexer' =
+      [ try lnewline
+      , try namespace
+      , try dot
+      , try identifier
+      , try keywordT
+      , try integerLiteral
+      , try stringLiteral
+      , assign
+      , colon
+      , backslash
+      , openParen
+      , closeParen
+      , openBracket
+      , closeBracket
+      ]
+
+lexTricu :: String -> [LToken]
+lexTricu input = case runParser tricuLexer "" input of
+  Left err -> errorWithoutStackTrace $ "Lexical error:\n" ++ errorBundlePretty err
+  Right tokens -> tokens
+
+
 keywordT :: Lexer LToken
 keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
 
 identifier :: Lexer LToken
 identifier = do
-  first <- letterChar <|> char '_'
+  first <- lowerChar <|> char '_'
   rest  <- many $ letterChar 
-              <|> digitChar 
-              <|> char '_' <|> char '-' <|> char '?' <|> char '.'
-              <|> char '$' <|> char '#' <|> char '@' <|> char '%'
+              <|> digitChar <|> char '_' <|> char '-' <|> char '?'
+              <|> char '$'  <|> char '#' <|> char '@' <|> char '%'
   let name = first : rest
   if (name == "t" || name == "!result")
     then fail "Keywords (`t`, `!result`) cannot be used as an identifier"
     else return (LIdentifier name)
 
-integerLiteral :: Lexer LToken
-integerLiteral = do
-  num <- some digitChar
-  return (LIntegerLiteral (read num))
+namespace :: Lexer LToken
+namespace = do
+  name <- try (string "!Local") <|> do
+    first <- upperChar
+    rest <- many (letterChar <|> digitChar)
+    return (first:rest)
+  return (LNamespace name)
 
-stringLiteral :: Lexer LToken
-stringLiteral = do
-  char '"'
-  content <- many (noneOf ['"'])
-  char '"' --"
-  return (LStringLiteral content)
-
-lModule :: Lexer LToken
-lModule = do
-  _ <- string "!module"
-  space1
-  LIdentifier moduleName <- identifier
-  return (LModule moduleName)
+dot :: Lexer LToken
+dot = char '.' *> pure LDot
 
 lImport :: Lexer LToken
 lImport = do
@@ -52,7 +84,7 @@ lImport = do
   space1
   LStringLiteral path <- stringLiteral
   space1
-  LIdentifier name <- identifier
+  LNamespace name <- namespace
   return (LImport path name)
 
 assign :: Lexer LToken
@@ -85,41 +117,15 @@ sc = space
   (skipLineComment "--")
   (skipBlockComment "|-" "-|")
 
-tricuLexer :: Lexer [LToken]
-tricuLexer = do
-  sc
-  header <- many $ do
-    tok <- choice
-      [ try lModule
-      , try lImport
-      , lnewline
-      ]
-    sc
-    pure tok
-  tokens <- many $ do
-    tok <- choice tricuLexer'
-    sc
-    pure tok
-  sc
-  eof
-  pure (header ++ tokens)
-  where
-    tricuLexer' =
-      [ try lnewline
-      , try identifier
-      , try keywordT
-      , try integerLiteral
-      , try stringLiteral
-      , assign
-      , colon
-      , backslash
-      , openParen
-      , closeParen
-      , openBracket
-      , closeBracket
-      ]
+integerLiteral :: Lexer LToken
+integerLiteral = do
+  num <- some digitChar
+  return (LIntegerLiteral (read num))
+
+stringLiteral :: Lexer LToken
+stringLiteral = do
+  char '"'
+  content <- many (noneOf ['"'])
+  char '"' --"
+  return (LStringLiteral content)
 
-lexTricu :: String -> [LToken]
-lexTricu input = case runParser tricuLexer "" input of
-  Left err -> errorWithoutStackTrace $ "Lexical error:\n" ++ errorBundlePretty err
-  Right tokens -> tokens