Chore(optimizer): add annotation tests for NVL (#6207)

* add annotation tests for NVL

* address comments

Author: fivetran-felixhuang

tests/dialects/test_snowflake.py

@@ -60,6 +60,7 @@ def test_snowflake(self):
         self.validate_identity("SELECT HEX_ENCODE('Hello World', 0)")
         self.validate_identity("SELECT NEXT_DAY('2025-10-15', 'FRIDAY')")
         self.validate_identity("SELECT NVL2(col1, col2, col3)")
+        self.validate_identity("SELECT NVL(col1, col2)", "SELECT COALESCE(col1, col2)")
         self.validate_identity("SELECT CHR(8364)")
         self.validate_identity("SELECT COMPRESS('Hello World', 'ZLIB')")
         self.validate_identity("SELECT DECOMPRESS_BINARY('compressed_data', 'SNAPPY')")

tests/fixtures/optimizer/annotate_functions.sql

@@ -2375,6 +2375,26 @@ VARCHAR;
 NVL2(col1, col2, col3);
 UNKNOWN;
 
+# dialect: snowflake
+NVL('hello', 'world');
+VARCHAR;
+
+# dialect: snowflake
+NVL(tbl.int_col, 42);
+INT;
+
+# dialect: snowflake
+NVL(tbl.date_col, CAST('2024-01-01' AS DATE));
+DATE;
+
+# dialect: snowflake
+NVL(1, 3.14);
+DOUBLE;
+
+# dialect: snowflake
+NVL(5::BIGINT, 2.71::FLOAT);
+FLOAT;
+
 # dialect: snowflake
 NULLIFZERO(5);
 INT;