Find escaped characters in strings

src/lexer/char.rs

@@ -10,6 +10,8 @@ pub trait Lexable {
     fn is_hash(&self) -> bool;
     fn is_dot(&self) -> bool;
     fn is_string_quote(&self) -> bool;
+    fn is_string_escape_leader(&self) -> bool;
+    fn is_string_escaped(&self) -> bool;
     fn is_newline(&self) -> bool;
     fn is_eof(&self) -> bool;
 
@@ -44,6 +46,14 @@ impl Lexable for char {
         *self == '"'
     }
 
+    fn is_string_escape_leader(&self) -> bool {
+        *self == '\\'
+    }
+
+    fn is_string_escaped(&self) -> bool {
+        *self == '"' || *self == '\\'
+    }
+
     fn is_boolean_true(&self) -> bool {
         *self == 't'
     }

src/lexer/mod.rs

@@ -38,6 +38,7 @@ enum State {
     NumberSign,
     Sign,
     String,
+    StringEscape,
 }
 
 pub struct Lexer {
@@ -357,6 +358,20 @@ impl Lexer {
         if c.is_string_quote() {
             return self.token_result(Token::String(self.value()));
         }
+        else if c.is_string_escape_leader() {
+            self.state = State::StringEscape;
+        }
+        Ok(None)
+    }
+
+    fn state_string_escape(&mut self, c: char) -> StateResult {
+        if c.is_string_escaped() {
+            self.state = State::String;
+            self.advance();
+        }
+        else {
+            return Err(self.error_string(format!("Invalid string escape character: {}", c)));
+        }
         Ok(None)
     }
 
@@ -402,6 +417,7 @@ impl Iterator for Lexer {
                 State::NumberSign => self.state_number_sign(c),
                 State::Sign => self.state_sign(c),
                 State::String => self.state_string(c),
+                State::StringEscape => self.state_string_escape(c),
                 State::Comment => self.state_comment(c),
             };
             assert!(result.has_token() || self.forward != previous_forward, "No lexing progress made!");
@@ -488,6 +504,12 @@ mod tests {
         check_single_token("\"abc\"", Token::String(String::from("\"abc\"")));
     }
 
+    #[test]
+    fn finds_escaped_characters_in_strings() {
+        check_single_token("\"\\\\\"", Token::String(String::from("\"\\\\\"")));
+        check_single_token("\"\\\"\"", Token::String(String::from("\"\\\"\"")));
+    }
+
     #[test]
     fn finds_numbers() {
         check_single_token(".34", Token::Number(Number::new(0.34)));