Remove unnecessary guard

Author: SubhamSinghal

datafusion/functions-aggregate/src/sum.rs

@@ -398,11 +398,6 @@ impl AggregateUDFImpl for Sum {
         if lit_type == DataType::Null {
             return Ok(None);
         }
-        // Skip the rewrite for interval: it requires `lit * COUNT(arg)`, but
-        // there is no generic Interval×Int64 multiplication kernel.
-        if matches!(lit_type, DataType::Interval(_)) {
-            return Ok(None);
-        }
 
         // Build up SUM(arg)
         let mut sum_agg = agg_function.clone();

datafusion/sqllogictest/test_files/aggregate.slt

@@ -6627,9 +6627,7 @@ SELECT sum(DISTINCT v) FROM (VALUES
 ----
 3 days
 
-# Regression: SUM(col + interval_lit) must NOT be rewritten to
-# SUM(col) + lit * COUNT(col) by simplify_expr_op_literal — there is no
-# Interval×Int64 multiplication kernel. Without the guard, this query fails.
+# SUM(col + interval_lit) — exercises the simplify_expr_op_literal path.
 query ?
 SELECT sum(v + interval '1 day') FROM (VALUES
   (interval '1 day'),