Fallback to identifier parsing if expression parsing fails (#1513)

Author: yoavcloud

src/dialect/mod.rs

@@ -681,6 +681,12 @@ pub trait Dialect: Debug + Any {
     fn supports_partiql(&self) -> bool {
         false
     }
+
+    /// Returns true if the specified keyword is reserved and cannot be
+    /// used as an identifier without special handling like quoting.
+    fn is_reserved_for_identifier(&self, kw: Keyword) -> bool {
+        keywords::RESERVED_FOR_IDENTIFIER.contains(&kw)
+    }
 }
 
 /// This represents the operators for which precedence must be defined

src/dialect/snowflake.rs

@@ -38,6 +38,8 @@ use alloc::vec::Vec;
 #[cfg(not(feature = "std"))]
 use alloc::{format, vec};
 
+use super::keywords::RESERVED_FOR_IDENTIFIER;
+
 /// A [`Dialect`] for [Snowflake](https://www.snowflake.com/)
 #[derive(Debug, Default)]
 pub struct SnowflakeDialect;
@@ -214,6 +216,16 @@ impl Dialect for SnowflakeDialect {
     fn supports_show_like_before_in(&self) -> bool {
         true
     }
+
+    fn is_reserved_for_identifier(&self, kw: Keyword) -> bool {
+        // Unreserve some keywords that Snowflake accepts as identifiers
+        // See: https://docs.snowflake.com/en/sql-reference/reserved-keywords
+        if matches!(kw, Keyword::INTERVAL) {
+            false
+        } else {
+            RESERVED_FOR_IDENTIFIER.contains(&kw)
+        }
+    }
 }
 
 /// Parse snowflake create table statement.

src/keywords.rs

@@ -948,3 +948,13 @@ pub const RESERVED_FOR_COLUMN_ALIAS: &[Keyword] = &[
     Keyword::INTO,
     Keyword::END,
 ];
+
+/// Global list of reserved keywords that cannot be parsed as identifiers
+/// without special handling like quoting. Parser should call `Dialect::is_reserved_for_identifier`
+/// to allow for each dialect to customize the list.
+pub const RESERVED_FOR_IDENTIFIER: &[Keyword] = &[
+    Keyword::EXISTS,
+    Keyword::INTERVAL,
+    Keyword::STRUCT,
+    Keyword::TRIM,
+];