Snowflake: parse DESCRIBE/DESC RESULT <query_id>

Add Statement::DescribeResult carrying a general expression argument so
both DESCRIBE RESULT '<id>' (string literal) and DESCRIBE RESULT
LAST_QUERY_ID() (function call) parse under SnowflakeDialect.

Author: hovaesco

src/ast/mod.rs

@@ -5216,6 +5216,19 @@ pub enum Statement {
         object_name: ObjectName,
     },
     /// ```sql
+    /// DESC | DESCRIBE RESULT <query_id>
+    /// ```
+    /// Snowflake-style `DESCRIBE RESULT '<query_id>'`, returning the column
+    /// metadata of a previously executed query's result set. The argument is a
+    /// general expression covering a string literal (`'01b...'`) and a function
+    /// call (`LAST_QUERY_ID()`).
+    DescribeResult {
+        /// `DESC` or `DESCRIBE`
+        describe_alias: DescribeAlias,
+        /// The query-id argument.
+        query_id: Box<Expr>,
+    },
+    /// ```sql
     /// [EXPLAIN | DESC | DESCRIBE]  <statement>
     /// ```
     Explain {
@@ -5754,6 +5767,12 @@ impl fmt::Display for Statement {
             } => {
                 write!(f, "{describe_alias} {object_type} {object_name}")
             }
+            Statement::DescribeResult {
+                describe_alias,
+                query_id,
+            } => {
+                write!(f, "{describe_alias} RESULT {query_id}")
+            }
             Statement::Explain {
                 describe_alias,
                 verbose,

src/ast/spans.rs

@@ -476,6 +476,7 @@ impl Spanned for Statement {
             Statement::Kill { .. } => Span::empty(),
             Statement::ExplainTable { .. } => Span::empty(),
             Statement::DescribeObject { .. } => Span::empty(),
+            Statement::DescribeResult { .. } => Span::empty(),
             Statement::Explain { .. } => Span::empty(),
             Statement::Savepoint { .. } => Span::empty(),
             Statement::ReleaseSavepoint { .. } => Span::empty(),

src/parser/mod.rs

@@ -14549,6 +14549,13 @@ impl<'a> Parser<'a> {
                         DescribeAlias::Desc | DescribeAlias::Describe
                     )
                 {
+                    if self.parse_keyword(Keyword::RESULT) {
+                        let query_id = self.parse_expr()?;
+                        return Ok(Statement::DescribeResult {
+                            describe_alias,
+                            query_id: Box::new(query_id),
+                        });
+                    }
                     if let Some(kw) = self.parse_one_of_keywords(&[
                         Keyword::TABLE,
                         Keyword::VIEW,