parser(postgres): support RETURNS SETOF in CREATE FUNCTION

Add a dedicated SETOF data type wrapper in the AST, teach the PostgreSQL CREATE FUNCTION parser to wrap return types after RETURNS SETOF, and register SETOF in the keyword table so parsing no longer relies on raw NoKeyword text matching.

Author: LucaCappelletti94

src/ast/data_type.rs

@@ -47,6 +47,10 @@ pub enum EnumMember {
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub enum DataType {
+    /// Set-returning function type in [PostgreSQL], e.g. CREATE FUNCTION RETURNS SETOF UUID.
+    ///
+    /// [PostgreSQL]: https://www.postgresql.org/docs/current/sql-createfunction.html
+    SetOf(Box<DataType>),
     /// Table type in [PostgreSQL], e.g. CREATE FUNCTION RETURNS TABLE(...).
     ///
     /// [PostgreSQL]: https://www.postgresql.org/docs/15/sql-createfunction.html
@@ -501,6 +505,7 @@ pub enum DataType {
 impl fmt::Display for DataType {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
+            DataType::SetOf(data_type) => write!(f, "SETOF {data_type}"),
             DataType::Character(size) => format_character_string_type(f, "CHARACTER", size),
             DataType::Char(size) => format_character_string_type(f, "CHAR", size),
             DataType::CharacterVarying(size) => {

src/keywords.rs

@@ -933,6 +933,7 @@ define_keywords!(
     SESSION_USER,
     SET,
     SETERROR,
+    SETOF,
     SETS,
     SETTINGS,
     SHARE,

src/parser/mod.rs

@@ -5581,7 +5581,13 @@ impl<'a> Parser<'a> {
         self.expect_token(&Token::RParen)?;
 
         let return_type = if self.parse_keyword(Keyword::RETURNS) {
-            Some(self.parse_data_type()?)
+            let setof = self.parse_keyword(Keyword::SETOF);
+            let return_type = self.parse_data_type()?;
+            Some(if setof {
+                DataType::SetOf(Box::new(return_type))
+            } else {
+                return_type
+            })
         } else {
             None
         };