Document: don't allow characters with unicode property Bidi_Class in …

…source files

Update documentation with changes made in scala#10017

spec/01-lexical-syntax.md

@@ -25,6 +25,9 @@ classes (Unicode general category given in parentheses):
 1. Operator characters. These consist of all printable ASCII characters
    (`\u0020` - `\u007E`) that are in none of the sets above, mathematical
    symbols (`Sm`) and other symbols (`So`).
+1. [Bidirectional explicit formatting](https://www.unicode.org/reports/tr9/#Bidirectional_Character_Types)
+   characters. The nine characters `\u202a - \u202e` and `\u2066 - \u2069`, 
+   inclusive. These are forbidden from appearing in character and string literals.
 
 ## Identifiers
 
@@ -413,12 +416,12 @@ members of type `Boolean`.
 ### Character Literals
 
 ```ebnf
-characterLiteral  ::=  ‘'’ (charNoQuoteOrNewline | escapeSeq) ‘'’
+characterLiteral  ::=  ‘'’ (charNoQuoteOrNewlineOrBidiFormatting | escapeSeq) ‘'’
 ```
 
 A character literal is a single character enclosed in quotes.
 The character can be any Unicode character except the single quote
-delimiter or `\u000A` (LF) or `\u000D` (CR);
+delimiter or `\u000A` (LF) or `\u000D` (CR) or a bidirectional formatting character;
 or any Unicode character represented by an
 [escape sequence](#escape-sequences).
 
@@ -430,12 +433,12 @@ or any Unicode character represented by an
 
 ```ebnf
 stringLiteral  ::=  ‘"’ {stringElement} ‘"’
-stringElement  ::=  charNoDoubleQuoteOrNewline | escapeSeq
+stringElement  ::=  charNoDoubleQuoteOrNewlineOrBidiFormatting | escapeSeq
 ```
 
 A string literal is a sequence of characters in double quotes.
 The characters can be any Unicode character except the double quote
-delimiter or `\u000A` (LF) or `\u000D` (CR);
+delimiter or `\u000A` (LF) or `\u000D` (CR) or a bidirectional formatting character;
 or any Unicode character represented by an [escape sequence](#escape-sequences).
 
 If the string literal contains a double quote character, it must be escaped using
@@ -452,14 +455,14 @@ The value of a string literal is an instance of class `String`.
 
 ```ebnf
 stringLiteral   ::=  ‘"""’ multiLineChars ‘"""’
-multiLineChars  ::=  {[‘"’] [‘"’] charNoDoubleQuote} {‘"’}
+multiLineChars  ::=  {[‘"’] [‘"’] charNoDoubleQuoteOrBidiFormatting} {‘"’}
 ```
 
 A multi-line string literal is a sequence of characters enclosed in
 triple quotes `""" ... """`. The sequence of characters is
 arbitrary, except that it may contain three or more consecutive quote characters
-only at the very end. Characters
-must not necessarily be printable; newlines or other
+only at the very end; the only forbidden Unicode characters are the bidirectional
+formatting ones. Characters must not necessarily be printable; newlines or other
 control characters are also permitted. [Escape sequences](#escape-sequences) are
 not processed, except for Unicode escapes (this is deprecated since 2.13.2).
 

spec/13-syntax-summary.md

@@ -28,6 +28,7 @@ opchar           ::=  ‘!’ | ‘#’ | ‘%’ | ‘&’ | ‘*’ | ‘+’
                       ‘<’ | ‘=’ | ‘>’ | ‘?’ | ‘@’ | ‘\’ | ‘^’ | ‘|’ | ‘~’
                       and any character in Unicode categories Sm or So
 printableChar    ::=  all characters in [\u0020, \u007E] inclusive
+bidiFormatting   ::=  all characters in [\u202a, \u202e] and [\u2066, \u2069], inclusive
 UnicodeEscape    ::=  ‘\’ ‘u’ {‘u’} hexDigit hexDigit hexDigit hexDigit
 hexDigit         ::=  ‘0’ | … | ‘9’ | ‘A’ | … | ‘F’ | ‘a’ | … | ‘f’
 charEscapeSeq    ::=  ‘\’ (‘b’ | ‘t’ | ‘n’ | ‘f’ | ‘r’ | ‘"’ | ‘'’ | ‘\’)
@@ -57,13 +58,14 @@ floatType        ::=  ‘F’ | ‘f’ | ‘D’ | ‘d’
 
 booleanLiteral   ::=  ‘true’ | ‘false’
 
-characterLiteral ::=  ‘'’ (charNoQuoteOrNewline | escapeSeq) ‘'’
+<<<<<<< HEAD
+characterLiteral ::=  ‘'’ (charNoQuoteOrNewlineOrBidiFormatting | escapeSeq) ‘'’
 
 stringLiteral    ::=  ‘"’ {stringElement} ‘"’
                    |  ‘"""’ multiLineChars ‘"""’
-stringElement    ::=  charNoDoubleQuoteOrNewline
+stringElement    ::=  charNoQuoteOrNewlineOrBidiFormatting
                    |  escapeSeq
-multiLineChars   ::=  {[‘"’] [‘"’] charNoDoubleQuote} {‘"’}
+multiLineChars   ::=  {[‘"’] [‘"’] charNoQuoteOrNewlineOrBidiFormatting} {‘"’}
 
 interpolatedString
                  ::=  alphaid ‘"’ {[‘\’] interpolatedStringPart | ‘\\’ | ‘\"’} ‘"’