[GitHub] [arrow] alamb commented on a change in pull request #8400: ARROW-10236: Unify type casting logic in DataFusion

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #8400:
URL: https://github.com/apache/arrow/pull/8400#discussion_r501795062



##########
File path: rust/datafusion/src/logical_plan/mod.rs
##########
@@ -323,12 +324,13 @@ impl Expr {
     ///
     /// # Errors
     ///
-    /// This function errors when it is impossible to cast the expression to the target [arrow::datatypes::DataType].
+    /// This function errors when it is impossible to cast the
+    /// expression to the target [arrow::datatypes::DataType].
     pub fn cast_to(&self, cast_to_type: &DataType, schema: &Schema) -> Result<Expr> {
         let this_type = self.get_type(schema)?;
         if this_type == *cast_to_type {
             Ok(self.clone())
-        } else if can_coerce_from(cast_to_type, &this_type) {
+        } else if can_cast_types(&this_type, cast_to_type) {

Review comment:
       the idea is to use a common `can_cast_types` function to detect valid casts at plan time, and make `can_cast_types` consistent with the arrow cast kernel




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