Properly catching an unclosed string in ANTLR4 - string-literals

Question

I have to define string literal in ANTLR4 and catch UNCLOSE_STRING exceptions.
Strings are surrounded by a pair of "" and have may have supported escapes:
\b \f \r \n \t \’ \\
The only way for " to appear inside a string is to be appended by a
' ('").
I have tried various ways to define a string literal but they were all catched by UNCLOSE_STRING:
program: global_variable_part function_declaration_part EOF;
<!-- Shenanigans of statements ...-->
fragment Character: ~( [\b\f\r\n\t"\\] | '\'') | Escape | '\'"';
fragment Escape: '\\' ( 'b' | 'f' | 'r' | 'n' | 't' | '\'' | '\\');
fragment IllegalEscape: '\\' ~( 'b' | 'f' | 'r' | 'n' | 't' | '\'' | '\\') ;
STR_LIT: '"' Character* '"' {
content = str(self.text)
self.text = content[1:-1]
};
UNCLOSE_STRING: '"' Character* ([\b\f\r\n\t\\] | EOF) {
esc = ['\b', '\t', '\n', '\f', '\r', '\\']
content = str(self.text)
raise UncloseString(content)
};
For example
"ab'"c\\n def" would match but only Unclosed String: ab'"c\n def" was produced.

Answer 1

This is quite close to the specification for Strings in Java. Don't be afraid to "borrow" from other grammars. I slight modification to the Java Lexer rules that (I think) matches your needs would be:
StringLiteral
: '"' StringCharacters? '"'
;
fragment
StringCharacters
: StringCharacter+
;
fragment
StringCharacter
: ~["\\\r\n]
| EscapeSequence
;
fragment
EscapeSequence
: '\\' [btnfr'\\]
: "\'"" // <-- the '" escape match
;
If you know of another language that's a closer match, you can look at how it was handled for looking for it's grammar here (ANTLR4 Grammars)