Add support for DuckDB struct literal syntax (#1194)

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

src/parser/mod.rs

@@ -1117,6 +1117,10 @@ impl<'a> Parser<'a> {
                 self.prev_token();
                 Ok(Expr::Value(self.parse_value()?))
             }
+            Token::LBrace if dialect_of!(self is DuckDbDialect | GenericDialect) => {
+                self.prev_token();
+                self.parse_duckdb_struct_literal()
+            }
             _ => self.expected("an expression:", next_token),
         }?;
 
@@ -2127,6 +2131,45 @@ impl<'a> Parser<'a> {
         ))
     }
 
+    /// DuckDB specific: Parse a duckdb dictionary [1]
+    ///
+    /// Syntax:
+    ///
+    /// ```sql
+    /// {'field_name': expr1[, ... ]}
+    /// ```
+    ///
+    /// [1]: https://duckdb.org/docs/sql/data_types/struct#creating-structs
+    fn parse_duckdb_struct_literal(&mut self) -> Result<Expr, ParserError> {
+        self.expect_token(&Token::LBrace)?;
+
+        let fields = self.parse_comma_separated(Self::parse_duckdb_dictionary_field)?;
+
+        self.expect_token(&Token::RBrace)?;
+
+        Ok(Expr::Dictionary(fields))
+    }
+
+    /// Parse a field for a duckdb dictionary [1]
+    /// Syntax
+    /// ```sql
+    /// 'name': expr
+    /// ```
+    ///
+    /// [1]: https://duckdb.org/docs/sql/data_types/struct#creating-structs
+    fn parse_duckdb_dictionary_field(&mut self) -> Result<DictionaryField, ParserError> {
+        let key = self.parse_identifier(false)?;
+
+        self.expect_token(&Token::Colon)?;
+
+        let expr = self.parse_expr()?;
+
+        Ok(DictionaryField {
+            key,
+            value: Box::new(expr),
+        })
+    }
+
     /// For nested types that use the angle bracket syntax, this matches either
     /// `>`, `>>` or nothing depending on which variant is expected (specified by the previously
     /// matched `trailing_bracket` argument). It returns whether there is a trailing