duckdb: support #N positional column references

Parse DuckDB's #1, #2 positional column references as Value::Placeholder.
DuckDB tokenizes # as Token::Sharp followed by a number.

Author: lustefaniak

corpus-fixes/003-expected-an-expression-found-token.md

@@ -36,7 +36,7 @@ SELECT untuple((* EXCEPT (v2, v3),)) FROM kv;
 
 ## databricks (3 files)
 
-- [ ] `sqlglot_databricks/select/0b4fcd7e5337.sql`
+- [x] `sqlglot_databricks/select/0b4fcd7e5337.sql`
 
   **Error:** `Expected an expression:, found: ]`
 
@@ -47,7 +47,9 @@ SELECT c1:item[*].price FROM VALUES ('{ "item": [ { "model" : "basic", "price" :
 
   ```
 
-- [ ] `sqlglot_databricks/select/67b14a6de0de.sql`
+  **Fix:** Added `Token::Mul` handling in `parse_snowflake_json_path` to emit `*` into the path string buffer, enabling `[*]` wildcard array subscript syntax in JSON paths.
+
+- [x] `sqlglot_databricks/select/67b14a6de0de.sql`
 
   **Error:** `Expected an expression:, found: ]`
 
@@ -58,7 +60,9 @@ SELECT INLINE(FROM_JSON(c1:item[*], 'ARRAY<STRUCT<model STRING, price DOUBLE>>')
 
   ```
 
-- [ ] `sqlglot_databricks/select/680db20c65dc.sql`
+  **Fix:** Same fix as above — `[*]` in JSON path now handled by `Token::Mul` in `parse_snowflake_json_path`.
+
+- [x] `sqlglot_databricks/select/680db20c65dc.sql`
 
   **Error:** `Expected an expression:, found: ]`
 
@@ -69,9 +73,11 @@ SELECT FROM_JSON(c1:item[*].price, 'ARRAY<DOUBLE>')[0] FROM VALUES ('{ "item": [
 
   ```
 
+  **Fix:** Same fix as above — `[*]` in JSON path now handled by `Token::Mul` in `parse_snowflake_json_path`.
+
 ## duckdb (7 files)
 
-- [ ] `sqlglot_duckdb/select/02b06713af25.sql`
+- [x] `sqlglot_duckdb/select/02b06713af25.sql`
 
   **Error:** `Expected an expression:, found: *`
 
@@ -82,6 +88,8 @@ SELECT UNNEST([*COLUMNS('alias_.*')]) AS column_name
 
   ```
 
+  **TOO HARD** — DuckDB's `*COLUMNS(...)` star replacement operator requires adding `Expr::Wildcard`/`Expr::StarReplacement` AST variants, since wildcards currently only exist in `FunctionArgExpr` and `SelectItem`, not in the general `Expr` enum. Only 1 corpus file affected.
+
 - [ ] `sqlglot_duckdb/select/1c2a1084cc5d.sql`
 
   **Error:** `Expected an expression:, found: #`

src/parser/mod.rs

@@ -984,6 +984,19 @@ impl<'a> Parser<'a> {
                     expr: Box::new(self.parse_subexpr(Self::MUL_DIV_MOD_OP_PREC)?),
                 })
             }
+            Token::Sharp if dialect_of!(self is DuckDbDialect) => {
+                // DuckDB positional reference: #1, #2, etc.
+                match self.peek_token().token {
+                    Token::Number(ref s, _) => {
+                        let s = format!("#{}", s);
+                        self.next_token();
+                        Ok(Expr::Value(Value::Placeholder(s)))
+                    }
+                    _ => {
+                        self.expected("a number after #", self.peek_token())?
+                    }
+                }
+            }
             Token::Tilde => {
                 Ok(Expr::UnaryOp {
                     op: UnaryOperator::PGBitwiseNot,

tests/sqlparser_duckdb.rs

@@ -402,3 +402,12 @@ fn test_trim_with_characters() {
     // DuckDB supports TRIM(expr, characters) syntax
     duckdb().verified_stmt("SELECT TRIM('***apple***', '*') AS result");
 }
+
+#[test]
+fn test_positional_reference() {
+    // DuckDB supports #N positional references
+    // Note: GenericDialect tokenizes #2 as identifier (since # is identifier_start),
+    // DuckDB tokenizes as Sharp + Number, so we only test DuckDB dialect.
+    duckdb().verified_stmt("SELECT #2 AS a, #1 AS b FROM (VALUES (1, 'foo'))");
+    duckdb().verified_stmt("SELECT #2, #1 FROM (VALUES (1, 'foo'))");
+}