Support different quoting styles for delimited identifiers

The dialect information is from https://en.wikibooks.org/wiki/SQL_Dialects_Reference/Data_structure_definition/Delimited_identifiers

src/dialect/mod.rs

@@ -8,8 +8,16 @@ pub use self::generic_sql::GenericSqlDialect;
 pub use self::postgresql::PostgreSqlDialect;
 
 pub trait Dialect {
-    /// Determine if a character is a valid identifier start character
+    /// Determine if a character starts a quoted identifier. The default
+    /// implementation, accepting "double quoted" ids is both ANSI-compliant
+    /// and appropriate for most dialects (with the notable exception of
+    /// MySQL, MS SQL, and sqlite). You can accept one of characters listed
+    /// in `SQLWord::matching_end_quote()` here
+    fn is_delimited_identifier_start(&self, ch: char) -> bool {
+        ch == '"'
+    }
+    /// Determine if a character is a valid start character for an unquoted identifier
     fn is_identifier_start(&self, ch: char) -> bool;
-    /// Determine if a character is a valid identifier character
+    /// Determine if a character is a valid unquoted identifier character
     fn is_identifier_part(&self, ch: char) -> bool;
 }

src/sqltokenizer.rs

@@ -163,13 +163,24 @@ pub struct SQLWord {
 impl ToString for SQLWord {
     fn to_string(&self) -> String {
         match self.quote_style {
-            Some('"') => format!("\"{}\"", self.value),
-            Some('[') => format!("[{}]", self.value),
+            Some(s) if s == '"' || s == '[' || s == '`' => {
+                format!("{}{}{}", s, self.value, SQLWord::matching_end_quote(s))
+            }
             None => self.value.clone(),
             _ => panic!("Unexpected quote_style!"),
         }
     }
 }
+impl SQLWord {
+    fn matching_end_quote(ch: char) -> char {
+        match ch {
+            '"' => '"', // ANSI and most dialects
+            '[' => ']', // MS SQL
+            '`' => '`', // MySQL
+            _ => panic!("unexpected quoting style!"),
+        }
+    }
+}
 
 #[derive(Debug, Clone, PartialEq)]
 pub enum Whitespace {
@@ -291,12 +302,13 @@ impl<'a> Tokenizer<'a> {
                     Ok(Some(Token::SingleQuotedString(s)))
                 }
                 // delimited (quoted) identifier
-                '"' => {
+                quote_start if self.dialect.is_delimited_identifier_start(quote_start) => {
                     let mut s = String::new();
-                    let quote_start = chars.next().unwrap(); // consumes the opening quote
+                    chars.next(); // consume the opening quote
+                    let quote_end = SQLWord::matching_end_quote(quote_start);
                     while let Some(ch) = chars.next() {
                         match ch {
-                            '"' => break,
+                            c if c == quote_end => break,
                             _ => s.push(ch),
                         }
                     }