fix: include dialect when parsing inside cast (tobymao#3960)

sqlglot/expressions.py

@@ -7249,8 +7249,8 @@ def cast(
     Returns:
         The new Cast instance.
     """
-    expr = maybe_parse(expression, copy=copy, **opts)
-    data_type = DataType.build(to, copy=copy, **opts)
+    expr = maybe_parse(expression, copy=copy, dialect=dialect, **opts)
+    data_type = DataType.build(to, copy=copy, dialect=dialect, **opts)
 
     # dont re-cast if the expression is already a cast to the correct type
     if isinstance(expr, Cast):

tests/test_expressions.py

@@ -451,6 +451,12 @@ def test_cast(self):
         self.assertEqual(len(list(recast.find_all(exp.Cast))), 2)
         self.assertEqual(recast.sql(), "CAST(CAST(x AS DATE) AS VARCHAR)")
 
+        # check that dialect is used when casting strings
+        self.assertEqual(
+            exp.cast("x", to="regtype", dialect="postgres").sql(), "CAST(x AS REGTYPE)"
+        )
+        self.assertEqual(exp.cast("`x`", to="date", dialect="hive").sql(), 'CAST("x" AS DATE)')
+
     def test_ctes(self):
         expression = parse_one("SELECT a FROM x")
         self.assertEqual(expression.ctes, [])