UTF letters are not accepted in symbol names

[majkrzak]

When defining a following type:

data Letter = A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z|Ä|Ö

code analizer screams with following error:

<constr>, <q name>, <top declaration>, HaskellTokenType.AT, HaskellTokenType.BACKQUOTE, HaskellTokenType.BACKSLASH, HaskellTokenType.CASE, HaskellTokenType.CHARACTER_LITERAL, HaskellTokenType.CLASS, HaskellTokenType.COLON_COLON, HaskellTokenType.COMMA, HaskellTokenType.DATA, HaskellTokenType.DECIMAL, HaskellTokenType.DEFAULT, HaskellTokenType.DERIVING, HaskellTokenType.DIRECTIVE, HaskellTokenType.DO, HaskellTokenType.DOT, HaskellTokenType.DOUBLE_QUOTES, HaskellTokenType.DOUBLE_RIGHT_ARROW, HaskellTokenType.ELSE, HaskellTokenType.EQUAL, HaskellTokenType.FLOAT, HaskellTokenType.HEXADECIMAL, HaskellTokenType.IF, HaskellTokenType.IMPORT, HaskellTokenType.IN, HaskellTokenType.INCLUDE_DIRECTIVE, HaskellTokenType.INFIX, HaskellTokenType.INFIXL, HaskellTokenType.INFIXR, HaskellTokenType.INSTANCE, HaskellTokenType.LEFT_ARROW, HaskellTokenType.LEFT_BRACE, HaskellTokenType.LEFT_BRACKET, HaskellTokenType.LEFT_PAREN, HaskellTokenType.LET, HaskellTokenType.LIST_COMPREHENSION, HaskellTokenType.MODULE, HaskellTokenType.NEWLINE, HaskellTokenType.NEWTYPE, HaskellTokenType.OCTAL, HaskellTokenType.OF, HaskellTokenType.PRAGMA_START, HaskellTokenType.QUASIQUOTE, HaskellTokenType.QUOTE, HaskellTokenType.RIGHT_ARROW, HaskellTokenType.RIGHT_BRACE, HaskellTokenType.RIGHT_BRACKET, HaskellTokenType.RIGHT_PAREN and ... expected, got 'Ä'

[majkrzak]

As far as I understand it is because lexer is only to Latin and Greek letters:

intellij-haskell/src/main/scala/intellij/haskell/_HaskellLexer.flex

Lines 45 to 46 in 6c1dc71

	small = [a-z] | {underscore} | [\u03B1-\u03C9] | 𝑖 | 𝕧 | µ | ¬
	large = [A-Z] | [\u0391-\u03A9] | ℝ | ℂ | ℕ | ℤ | ℚ

Accoriding to Haskell 2010 Report §2.2 it should support "any Unicode lowercase letter" and "any uppercase or titlecase Unicode letter" accordingly.