fix: UTF8 cast error

crates/polars-core/src/datatypes/any_value.rs

@@ -457,7 +457,6 @@ impl<'a> AnyValue<'a> {
                     DataType::Duration(tu) => AnyValue::Duration($av as i64, *tu),
                     #[cfg(feature="dtype-time")]
                     DataType::Time => AnyValue::Time($av as i64),
-                    DataType::Utf8 => AnyValue::Utf8Owned(format_smartstring!("{}", $av)),
                     _ => polars_bail!(
                         ComputeError: "cannot cast any-value {:?} to dtype '{}'", self, dtype,
                     ),
@@ -467,6 +466,7 @@ impl<'a> AnyValue<'a> {
         );
 
         let new_av = match self {
+            AnyValue::Utf8(v) => AnyValue::Utf8Owned(format_smartstring!("{}", v)),
             AnyValue::Boolean(v) => cast_to!(*v as u8),
             AnyValue::Float32(_) | AnyValue::Float64(_) => cast_to!(self.extract::<f64>().unwrap()),
             av if av.is_signed() => cast_to!(av.extract::<i64>().unwrap()),

crates/polars-sql/tests/simple_exprs.rs

@@ -504,6 +504,23 @@ fn test_group_by_2() -> PolarsResult<()> {
     Ok(())
 }
 
+#[test]
+fn test_cast_and_str_concat_expr(){
+    let a = Series::new("a", vec!["hello"]);
+    let df  = DataFrame::new(vec![a]).unwrap();
+    let mut context = SQLContext::new();
+    context.register("df", df.clone().lazy()); 
+    let sql = r#"
+    SELECT
+        a || ' world' as a_v2,
+        'hello' || ' world' as a_v3
+    FROM df"#;
+    let df_sql = context.execute(sql).unwrap().collect().unwrap();
+
+    assert_eq!(Series::new("a_v2", vec!["hello world"]),*df_sql.column("a_v2").unwrap());
+    assert_eq!(Series::new("a_v3", vec!["hello world"]),*df_sql.column("a_v3").unwrap());
+}
+
 #[test]
 fn test_case_expr() {
     let df = create_sample_df().unwrap().head(Some(10));