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'
     }