Fix literal-leading dialect override expressions

Author: LucaCappelletti94

derive/src/dialect.rs

@@ -76,12 +76,16 @@ impl Parse for DeriveDialectInput {
                         while !content.is_empty() {
                             let key: Ident = content.parse()?;
                             content.parse::<Token![=]>()?;
-                            let value = if content.peek(LitBool) {
-                                Override::Bool(content.parse()?)
-                            } else if content.peek(LitChar) {
-                                Override::Char(content.parse()?)
-                            } else {
-                                Override::Expr(content.parse()?)
+                            let value = match content.parse::<Expr>()? {
+                                Expr::Lit(syn::ExprLit {
+                                    lit: syn::Lit::Bool(value),
+                                    ..
+                                }) => Override::Bool(value),
+                                Expr::Lit(syn::ExprLit {
+                                    lit: syn::Lit::Char(value),
+                                    ..
+                                }) => Override::Char(value),
+                                expr => Override::Expr(expr),
                             };
                             overrides.push((key, value));
                             if content.peek(Token![,]) {

src/dialect/mod.rs

@@ -117,7 +117,9 @@ pub use self::teradata::TeradataDialect;
 /// use sqlparser::dialect::{BindPlaceholderStyle, Dialect, GenericDialect};
 ///
 /// derive_dialect!(DollarBindDialect, GenericDialect,
-///     overrides = { ordered_bind_placeholder_style = Some(BindPlaceholderStyle::DollarNumbered) }
+///     overrides = {
+///         ordered_bind_placeholder_style = true.then_some(BindPlaceholderStyle::DollarNumbered)
+///     }
 /// );
 /// let d: &dyn Dialect = &DollarBindDialect::new();
 /// assert_eq!(

tests/sqlparser_derive_dialect.rs

@@ -194,3 +194,29 @@ fn test_lambda_keyword_syntax_with_json_arrow_operator() {
     };
     assert_eq!(&BinaryOperator::Arrow, op);
 }
+
+#[test]
+fn test_literal_leading_char_expression_override() {
+    derive_dialect!(LiteralExpressionDialect, GenericDialect, overrides = {
+        is_identifier_start = '_' == ch || ch.is_ascii_alphabetic(),
+    });
+    let dialect = LiteralExpressionDialect::new();
+
+    assert!(dialect.is_identifier_start('_'));
+    assert!(dialect.is_identifier_start('a'));
+    assert!(!dialect.is_identifier_start('1'));
+}
+
+#[test]
+fn test_literal_leading_bool_expression_override() {
+    derive_dialect!(LiteralExpressionDialect, GenericDialect, overrides = {
+        ordered_bind_placeholder_style =
+            true.then_some(sqlparser::dialect::BindPlaceholderStyle::DollarNumbered),
+    });
+    let dialect = LiteralExpressionDialect::new();
+
+    assert_eq!(
+        dialect.ordered_bind_placeholder_style(),
+        Some(sqlparser::dialect::BindPlaceholderStyle::DollarNumbered)
+    );
+}