vbarua commented on code in PR #15854:
URL: https://github.com/apache/datafusion/pull/15854#discussion_r2067014140


##########
datafusion/substrait/src/logical_plan/producer.rs:
##########
@@ -1590,6 +1590,21 @@ pub fn from_cast(
     schema: &DFSchemaRef,
 ) -> Result<Expression> {
     let Cast { expr, data_type } = cast;
+    // since substrait Null must be typed, so if we see a cast(null, dt), we 
make it a typed null
+    if let Expr::Literal(lit) = expr.as_ref() {
+        if lit.is_null() {

Review Comment:
   To further clarify, at the SQL/Relational level
   ```sql
   SELECT null::text[], array[]::text[]
   
   text | array
   ---- | --
   null | {}
   ```
   we can distinguish between casting a null literal to a compound type, and 
the empty version of that compound type.
   
   [dbfiddle](https://www.db-fiddle.com/f/cH7Hwk6mHnm3rgy7wXG4Yq/47)



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