chore: exists statement ast refactored

Author: Almaz-KG

src/ast/expression/mod.rs

@@ -278,14 +278,12 @@ pub enum InExpressionType {
     TableFunction(Identifier, Vec<Expression>),
 }
 
-/// An exists statement type
+/// An exists statement, i.e. $expr EXISTS (select statement)
 #[derive(Debug, PartialEq, Clone)]
-pub enum ExistsStatement {
-    /// Exists
-    Exists(SelectStatement),
+pub struct ExistsStatement {
+    pub select_statement: SelectStatement,
 
-    /// Not Exists
-    NotExists(SelectStatement),
+    pub not: bool,
 }
 
 /// A case expression

src/parser/expression/exists_expr.rs

@@ -20,13 +20,10 @@ impl ExistsExpressionParser for Parser<'_> {
         // Consume the enclosing right parenthesis
         self.consume_as(TokenType::RightParen)?;
 
-        let exists_statement = if is_not {
-            ExistsStatement::NotExists(select_statement)
-        } else {
-            ExistsStatement::Exists(select_statement)
-        };
-
-        Ok(Expression::ExistsStatement(exists_statement))
+        Ok(Expression::ExistsStatement(ExistsStatement {
+            select_statement,
+            not: is_not,
+        }))
     }
 }
 

src/parser/expression/mod.rs

@@ -374,10 +374,9 @@ pub(crate) mod test_utils {
     }
 
     pub fn exist_expr(is_not: bool, statement: SelectStatement) -> Expression {
-        Expression::ExistsStatement(if is_not {
-            ExistsStatement::NotExists(statement)
-        } else {
-            ExistsStatement::Exists(statement)
+        Expression::ExistsStatement(ExistsStatement {
+            select_statement: statement,
+            not: is_not,
         })
     }