Use #[default] enums, MSRV is 1.78 as of #4008

diesel/src/insertable.rs

@@ -135,10 +135,11 @@ impl<Col, Expr> ColumnInsertValue<Col, Expr> {
     }
 }
 
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Default, Copy, Clone)]
 #[doc(hidden)]
 pub enum DefaultableColumnInsertValue<T> {
     Expression(T),
+    #[default]
     Default,
 }
 
@@ -147,13 +148,6 @@ impl<T> QueryId for DefaultableColumnInsertValue<T> {
     const HAS_STATIC_QUERY_ID: bool = false;
 }
 
-#[allow(clippy::derivable_impls)] // that's not supported on rust 1.65
-impl<T> Default for DefaultableColumnInsertValue<T> {
-    fn default() -> Self {
-        DefaultableColumnInsertValue::Default
-    }
-}
-
 impl<Col, Expr, DB> InsertValues<DB, Col::Table>
     for DefaultableColumnInsertValue<ColumnInsertValue<Col, Expr>>
 where

diesel_cli/src/config.rs

@@ -570,20 +570,14 @@ impl MigrationsDirectory {
 
 type Regex = RegexWrapper<::regex::Regex>;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Default)]
 pub enum Filtering {
     OnlyTables(Vec<Regex>),
     ExceptTables(Vec<Regex>),
+    #[default]
     None,
 }
 
-#[allow(clippy::derivable_impls)] // that's not supported on rust 1.65
-impl Default for Filtering {
-    fn default() -> Self {
-        Filtering::None
-    }
-}
-
 impl Filtering {
     pub fn should_ignore_table(&self, name: &TableName) -> bool {
         use self::Filtering::*;

diesel_cli/src/print_schema.rs

@@ -12,55 +12,37 @@ use std::str;
 const SCHEMA_HEADER: &str = "// @generated automatically by Diesel CLI.\n";
 
 /// How to sort columns when querying the table schema.
-#[derive(Debug, Deserialize, Serialize, Clone, Copy)]
+#[derive(Debug, Default, Deserialize, Serialize, Clone, Copy)]
 pub enum ColumnSorting {
     /// Order by ordinal position
     #[serde(rename = "ordinal_position")]
+    #[default]
     OrdinalPosition,
     /// Order by column name
     #[serde(rename = "name")]
     Name,
 }
 
-#[allow(clippy::derivable_impls)] // that's not supported on rust 1.65
-impl Default for ColumnSorting {
-    fn default() -> Self {
-        ColumnSorting::OrdinalPosition
-    }
-}
-
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, Default)]
 pub enum DocConfig {
     DatabaseCommentsFallbackToAutoGeneratedDocComment,
     OnlyDatabaseComments,
+    #[default]
     NoDocComments,
 }
 
-#[allow(clippy::derivable_impls)] // that's not supported on rust 1.65
-impl Default for DocConfig {
-    fn default() -> Self {
-        DocConfig::NoDocComments
-    }
-}
-
 /// How to group tables in `allow_tables_to_appear_in_same_query!()`.
-#[derive(Debug, Deserialize, Serialize, Clone, Copy)]
+#[derive(Debug, Default, Deserialize, Serialize, Clone, Copy)]
 pub enum AllowTablesToAppearInSameQueryConfig {
     /// Group by foreign key relations
     #[serde(rename = "fk_related_tables")]
     FkRelatedTables,
     /// List all tables in invocation
     #[serde(rename = "all_tables")]
+    #[default]
     AllTables,
 }
 
-#[allow(clippy::derivable_impls)] // that's not supported on rust 1.65
-impl Default for AllowTablesToAppearInSameQueryConfig {
-    fn default() -> Self {
-        AllowTablesToAppearInSameQueryConfig::AllTables
-    }
-}
-
 pub fn run_print_schema<W: IoWrite>(
     connection: &mut InferConnection,
     config: &config::PrintSchema,