From 8483b76739abe5daf277ecfa5d1b7ed942de33aa Mon Sep 17 00:00:00 2001
From: jayzhan211 <jayzhan211@gmail.com>
Date: Mon, 4 Dec 2023 09:18:20 +0800
Subject: [PATCH] improve comment

Signed-off-by: jayzhan211 <jayzhan211@gmail.com>
---
 datafusion/common/src/utils.rs   | 24 +++++++++++++-----------
 datafusion/expr/src/signature.rs |  6 ++++--
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/datafusion/common/src/utils.rs b/datafusion/common/src/utils.rs
index b97ec868edd47..a10428a7224ef 100644
--- a/datafusion/common/src/utils.rs
+++ b/datafusion/common/src/utils.rs
@@ -427,7 +427,7 @@ pub fn base_type(data_type: &DataType) -> DataType {
     }
 }
 
-/// Coerced only the base type.
+/// A helper function to coerce base type in List.
 ///
 /// Example
 /// ```
@@ -444,18 +444,20 @@ pub fn coerced_type_with_base_type_only(
     base_type: &DataType,
 ) -> DataType {
     match data_type {
-        DataType::List(field) => match field.data_type() {
-            DataType::List(_) => DataType::List(Arc::new(Field::new(
-                field.name(),
-                coerced_type_with_base_type_only(field.data_type(), base_type),
-                field.is_nullable(),
-            ))),
-            _ => DataType::List(Arc::new(Field::new(
+        DataType::List(field) => {
+            let data_type = match field.data_type() {
+                DataType::List(_) => {
+                    coerced_type_with_base_type_only(field.data_type(), base_type)
+                }
+                _ => base_type.to_owned(),
+            };
+
+            DataType::List(Arc::new(Field::new(
                 field.name(),
-                base_type.clone(),
+                data_type,
                 field.is_nullable(),
-            ))),
-        },
+            )))
+        }
 
         _ => base_type.clone(),
     }
diff --git a/datafusion/expr/src/signature.rs b/datafusion/expr/src/signature.rs
index 8c5fff507ea06..2e0e4ca731c44 100644
--- a/datafusion/expr/src/signature.rs
+++ b/datafusion/expr/src/signature.rs
@@ -140,14 +140,16 @@ impl TypeSignature {
                     .collect::<Vec<&str>>()
                     .join(", ")]
             }
-            TypeSignature::VariadicCoerced => vec!["CoercibleT, .., CoercibleT".to_string()],
+            TypeSignature::VariadicCoerced => {
+                vec!["CoercibleT, .., CoercibleT".to_string()]
+            }
             TypeSignature::VariadicEqual => vec!["T, .., T".to_string()],
             TypeSignature::VariadicAny => vec!["Any, .., Any".to_string()],
             TypeSignature::OneOf(sigs) => {
                 sigs.iter().flat_map(|s| s.to_string_repr()).collect()
             }
             TypeSignature::ArrayAppendLikeSignature => {
-                vec!["ArrayAppendLikeSignature".to_string()]
+                vec!["ArrayAppendLikeSignature(List<T>, T)".to_string()]
             }
         }
     }