Deparser: Add parens around TypeCast in IndexElem

We were incorrectly omitting these parentheses, as well as missing a space
outputting "CREATE INDEX ON t (col::typecastops_class)" instead of
"CREATE INDEX ON t ((col::typecast) ops_class)".

Fixes #213

src/postgres_deparse.c

@@ -1826,14 +1826,15 @@ static void deparseIndexElem(StringInfo str, IndexElem* index_elem)
 	{
 		switch (nodeTag(index_elem->expr))
 		{
-			case T_FuncCall:
-			case T_SQLValueFunction:
-			case T_TypeCast:
-			case T_CoalesceExpr:
-			case T_MinMaxExpr:
-			case T_XmlExpr:
-			case T_XmlSerialize:
+			// Simple function calls can be written without wrapping parens
+			case T_FuncCall: // func_application
+			case T_SQLValueFunction: // func_expr_common_subexpr
+			case T_CoalesceExpr: // func_expr_common_subexpr
+			case T_MinMaxExpr: // func_expr_common_subexpr
+			case T_XmlExpr: // func_expr_common_subexpr
+			case T_XmlSerialize: // func_expr_common_subexpr
 				deparseFuncExprWindowless(str, index_elem->expr);
+				appendStringInfoString(str, " ");
 				break;
 			default:
 				appendStringInfoChar(str, '(');

test/deparse_tests.c

@@ -400,6 +400,7 @@ const char* tests[] = {
   "SELECT 1 FROM tbl LIMIT COALESCE($1, $2)",
   "SELECT (false AND true) IS FALSE",
   "SELECT a = (true IS FALSE)",
+  "CREATE INDEX myindex ON public.mytable USING btree (col1, (col2::varchar) varchar_pattern_ops)"
 };
 
 size_t testsLength = __LINE__ - 4;