clippy: fix clippy lints for 1.83

- derive(FromPrimitive) does not work with new clippy. Need to implement it manually
  We can maybe revert it in the future. However, this change is not a big deal.
- Converted all manually created c-strings to c"" literals
- Removed some unnecessary return statements detected by clippy

scylla-rust-wrapper/src/cluster.rs

@@ -1070,6 +1070,8 @@ mod tests {
                     );
 
                     // empty strings
+                    // Allow it, since c"" somehow clashes with #[ntest] proc macro...
+                    #[allow(clippy::manual_c_str_literals)]
                     let empty_str = "\0".as_ptr() as *const i8;
                     assert_cass_error_eq!(
                         cass_cluster_set_load_balance_dc_aware(cluster_raw, std::ptr::null(), 0, 0),

scylla-rust-wrapper/src/exec_profile.rs

@@ -528,7 +528,7 @@ mod tests {
                     assert_cass_error_eq!(
                         cass_execution_profile_set_load_balance_dc_aware(
                             profile_raw,
-                            "eu\0".as_ptr() as *const i8,
+                            c"eu".as_ptr(),
                             0,
                             0
                         ),
@@ -562,7 +562,7 @@ mod tests {
                     assert_cass_error_eq!(
                         cass_execution_profile_set_load_balance_dc_aware(
                             profile_raw,
-                            "eu\0".as_ptr() as *const i8,
+                            c"eu".as_ptr(),
                             1,
                             0
                         ),
@@ -571,7 +571,7 @@ mod tests {
                     assert_cass_error_eq!(
                         cass_execution_profile_set_load_balance_dc_aware(
                             profile_raw,
-                            "eu\0".as_ptr() as *const i8,
+                            c"eu".as_ptr(),
                             0,
                             1
                         ),

scylla-rust-wrapper/src/inet.rs

@@ -1,7 +1,6 @@
 use crate::argconv::*;
 use crate::cass_error::CassError;
 use crate::types::*;
-use num_derive::FromPrimitive;
 use num_traits::FromPrimitive;
 use std::convert::TryFrom;
 use std::convert::TryInto;
@@ -14,12 +13,33 @@ pub(crate) use crate::cass_inet_types::CassInet;
 
 #[repr(u8)] // address_length field in CassInet is cass_uint8_t
 #[allow(non_camel_case_types)]
-#[derive(Debug, Copy, Clone, FromPrimitive)]
+#[derive(Debug, Copy, Clone)]
 pub enum CassInetLength {
     CASS_INET_V4 = 4,
     CASS_INET_V6 = 16,
 }
 
+// Need to implement manually, because of the clippy 0.1.83 lints:
+// | `FromPrimitive` is not local
+// | move the `impl` block outside of this constant `_IMPL_NUM_FromPrimitive_FOR_CassInetLength`
+impl FromPrimitive for CassInetLength {
+    fn from_i64(n: i64) -> Option<Self> {
+        match n {
+            4 => Some(Self::CASS_INET_V4),
+            16 => Some(Self::CASS_INET_V6),
+            _ => None,
+        }
+    }
+
+    fn from_u64(n: u64) -> Option<Self> {
+        match n {
+            4 => Some(Self::CASS_INET_V4),
+            16 => Some(Self::CASS_INET_V6),
+            _ => None,
+        }
+    }
+}
+
 unsafe fn cass_inet_init(address: *const cass_uint8_t, address_length: CassInetLength) -> CassInet {
     let mut array = [0; 16];
     let length = address_length as usize;

scylla-rust-wrapper/src/logging.rs

@@ -113,7 +113,7 @@ where
             severity: (*event.metadata().level()).into(),
             file: target.as_ptr() as *const c_char,
             line: event.metadata().line().unwrap_or(0) as i32,
-            function: "\0".as_ptr() as *const c_char, // ignored, as cannot be fetched from event metadata
+            function: c"".as_ptr() as *const c_char, // ignored, as cannot be fetched from event metadata
             message: str_to_arr(message),
         };
 

scylla-rust-wrapper/src/query_result.rs

@@ -1106,7 +1106,7 @@ pub unsafe extern "C" fn cass_row_get_column_by_name_n(
         is_case_sensitive = true;
     }
 
-    return row_from_raw
+    row_from_raw
         .result_metadata
         .col_specs
         .iter()
@@ -1115,13 +1115,11 @@ pub unsafe extern "C" fn cass_row_get_column_by_name_n(
             is_case_sensitive && col_spec.name == name_str
                 || !is_case_sensitive && col_spec.name.eq_ignore_ascii_case(name_str)
         })
-        .map(|(index, _)| {
-            return match row_from_raw.columns.get(index) {
-                Some(value) => value as *const CassValue,
-                None => std::ptr::null(),
-            };
+        .map(|(index, _)| match row_from_raw.columns.get(index) {
+            Some(value) => value as *const CassValue,
+            None => std::ptr::null(),
         })
-        .unwrap_or(std::ptr::null());
+        .unwrap_or(std::ptr::null())
 }
 
 #[no_mangle]