Merge #9846

9846: feat: Generate default trait fn impl when generating `Clone` r=Veykril a=yoshuawuyts

Implements a default trait function body when generating the `Clone` trait for a type. Thanks!

r? `@\veykril`

Co-authored-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

Author: bors[bot]

crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs

@@ -443,6 +443,169 @@ impl core::hash::Hash for Foo {
         core::mem::discriminant(self).hash(state);
     }
 }
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_clone_record_struct() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: clone
+#[derive(Clo$0ne)]
+struct Foo {
+    bin: usize,
+    bar: usize,
+}
+"#,
+            r#"
+struct Foo {
+    bin: usize,
+    bar: usize,
+}
+
+impl Clone for Foo {
+    $0fn clone(&self) -> Self {
+        Self { bin: self.bin.clone(), bar: self.bar.clone() }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_clone_tuple_struct() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: clone
+#[derive(Clo$0ne)]
+struct Foo(usize, usize);
+"#,
+            r#"
+struct Foo(usize, usize);
+
+impl Clone for Foo {
+    $0fn clone(&self) -> Self {
+        Self(self.0.clone(), self.1.clone())
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_clone_empty_struct() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: clone
+#[derive(Clo$0ne)]
+struct Foo;
+"#,
+            r#"
+struct Foo;
+
+impl Clone for Foo {
+    $0fn clone(&self) -> Self {
+        Self {  }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_clone_enum() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: clone
+#[derive(Clo$0ne)]
+enum Foo {
+    Bar,
+    Baz,
+}
+"#,
+            r#"
+enum Foo {
+    Bar,
+    Baz,
+}
+
+impl Clone for Foo {
+    $0fn clone(&self) -> Self {
+        match self {
+            Self::Bar => Self::Bar,
+            Self::Baz => Self::Baz,
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_clone_tuple_enum() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: clone
+#[derive(Clo$0ne)]
+enum Foo {
+    Bar(String),
+    Baz,
+}
+"#,
+            r#"
+enum Foo {
+    Bar(String),
+    Baz,
+}
+
+impl Clone for Foo {
+    $0fn clone(&self) -> Self {
+        match self {
+            Self::Bar(arg0) => Self::Bar(arg0.clone()),
+            Self::Baz => Self::Baz,
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_clone_record_enum() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: clone
+#[derive(Clo$0ne)]
+enum Foo {
+    Bar {
+        bin: String,
+    },
+    Baz,
+}
+"#,
+            r#"
+enum Foo {
+    Bar {
+        bin: String,
+    },
+    Baz,
+}
+
+impl Clone for Foo {
+    $0fn clone(&self) -> Self {
+        match self {
+            Self::Bar { bin } => Self::Bar { bin: bin.clone() },
+            Self::Baz => Self::Baz,
+        }
+    }
+}
 "#,
         )
     }

crates/ide_assists/src/utils/gen_trait_fn_body.rs

@@ -16,13 +16,127 @@ pub(crate) fn gen_trait_fn_body(
     adt: &ast::Adt,
 ) -> Option<()> {
     match trait_path.segment()?.name_ref()?.text().as_str() {
+        "Clone" => gen_clone_impl(adt, func),
         "Debug" => gen_debug_impl(adt, func),
         "Default" => gen_default_impl(adt, func),
         "Hash" => gen_hash_impl(adt, func),
         _ => None,
     }
 }
 
+/// Generate a `Clone` impl based on the fields and members of the target type.
+fn gen_clone_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
+    fn gen_clone_call(target: ast::Expr) -> ast::Expr {
+        let method = make::name_ref("clone");
+        make::expr_method_call(target, method, make::arg_list(None))
+    }
+    let expr = match adt {
+        // `Clone` cannot be derived for unions, so no default impl can be provided.
+        ast::Adt::Union(_) => return None,
+        ast::Adt::Enum(enum_) => {
+            let list = enum_.variant_list()?;
+            let mut arms = vec![];
+            for variant in list.variants() {
+                let name = variant.name()?;
+                let left = make::ext::ident_path("Self");
+                let right = make::ext::ident_path(&format!("{}", name));
+                let variant_name = make::path_concat(left, right);
+
+                match variant.field_list() {
+                    // => match self { Self::Name { x } => Self::Name { x: x.clone() } }
+                    Some(ast::FieldList::RecordFieldList(list)) => {
+                        let mut pats = vec![];
+                        let mut fields = vec![];
+                        for field in list.fields() {
+                            let field_name = field.name()?;
+                            let pat = make::ident_pat(false, false, field_name.clone());
+                            pats.push(pat.into());
+
+                            let path = make::ext::ident_path(&field_name.to_string());
+                            let method_call = gen_clone_call(make::expr_path(path));
+                            let name_ref = make::name_ref(&field_name.to_string());
+                            let field = make::record_expr_field(name_ref, Some(method_call));
+                            fields.push(field);
+                        }
+                        let pat = make::record_pat(variant_name.clone(), pats.into_iter());
+                        let fields = make::record_expr_field_list(fields);
+                        let record_expr = make::record_expr(variant_name, fields).into();
+                        arms.push(make::match_arm(Some(pat.into()), None, record_expr));
+                    }
+
+                    // => match self { Self::Name(arg1) => Self::Name(arg1.clone()) }
+                    Some(ast::FieldList::TupleFieldList(list)) => {
+                        let mut pats = vec![];
+                        let mut fields = vec![];
+                        for (i, _) in list.fields().enumerate() {
+                            let field_name = format!("arg{}", i);
+                            let pat = make::ident_pat(false, false, make::name(&field_name));
+                            pats.push(pat.into());
+
+                            let f_path = make::expr_path(make::ext::ident_path(&field_name));
+                            fields.push(gen_clone_call(f_path));
+                        }
+                        let pat = make::tuple_struct_pat(variant_name.clone(), pats.into_iter());
+                        let struct_name = make::expr_path(variant_name);
+                        let tuple_expr = make::expr_call(struct_name, make::arg_list(fields));
+                        arms.push(make::match_arm(Some(pat.into()), None, tuple_expr));
+                    }
+
+                    // => match self { Self::Name => Self::Name }
+                    None => {
+                        let pattern = make::path_pat(variant_name.clone());
+                        let variant_expr = make::expr_path(variant_name);
+                        arms.push(make::match_arm(Some(pattern.into()), None, variant_expr));
+                    }
+                }
+            }
+
+            let match_target = make::expr_path(make::ext::ident_path("self"));
+            let list = make::match_arm_list(arms).indent(ast::edit::IndentLevel(1));
+            make::expr_match(match_target, list)
+        }
+        ast::Adt::Struct(strukt) => {
+            match strukt.field_list() {
+                // => Self { name: self.name.clone() }
+                Some(ast::FieldList::RecordFieldList(field_list)) => {
+                    let mut fields = vec![];
+                    for field in field_list.fields() {
+                        let base = make::expr_path(make::ext::ident_path("self"));
+                        let target = make::expr_field(base, &field.name()?.to_string());
+                        let method_call = gen_clone_call(target);
+                        let name_ref = make::name_ref(&field.name()?.to_string());
+                        let field = make::record_expr_field(name_ref, Some(method_call));
+                        fields.push(field);
+                    }
+                    let struct_name = make::ext::ident_path("Self");
+                    let fields = make::record_expr_field_list(fields);
+                    make::record_expr(struct_name, fields).into()
+                }
+                // => Self(self.0.clone(), self.1.clone())
+                Some(ast::FieldList::TupleFieldList(field_list)) => {
+                    let mut fields = vec![];
+                    for (i, _) in field_list.fields().enumerate() {
+                        let f_path = make::expr_path(make::ext::ident_path("self"));
+                        let target = make::expr_field(f_path, &format!("{}", i)).into();
+                        fields.push(gen_clone_call(target));
+                    }
+                    let struct_name = make::expr_path(make::ext::ident_path("Self"));
+                    make::expr_call(struct_name, make::arg_list(fields))
+                }
+                // => Self { }
+                None => {
+                    let struct_name = make::ext::ident_path("Self");
+                    let fields = make::record_expr_field_list(None);
+                    make::record_expr(struct_name, fields).into()
+                }
+            }
+        }
+    };
+    let body = make::block_expr(None, Some(expr)).indent(ast::edit::IndentLevel(1));
+    ted::replace(func.body()?.syntax(), body.clone_for_update().syntax());
+    Some(())
+}
+
 /// Generate a `Debug` impl based on the fields and members of the target type.
 fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
     let annotated_name = adt.name()?;
@@ -88,10 +202,10 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
                 Some(ast::FieldList::TupleFieldList(field_list)) => {
                     let method = make::name_ref("debug_tuple");
                     let mut expr = make::expr_method_call(target, method, args);
-                    for (idx, _) in field_list.fields().enumerate() {
+                    for (i, _) in field_list.fields().enumerate() {
                         let f_path = make::expr_path(make::ext::ident_path("self"));
                         let f_path = make::expr_ref(f_path, false);
-                        let f_path = make::expr_field(f_path, &format!("{}", idx)).into();
+                        let f_path = make::expr_field(f_path, &format!("{}", i)).into();
                         let method = make::name_ref("field");
                         expr = make::expr_method_call(expr, method, make::arg_list(Some(f_path)));
                     }
@@ -182,7 +296,7 @@ fn gen_hash_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
             make::block_expr(Some(stmt), None).indent(ast::edit::IndentLevel(1))
         }
         ast::Adt::Struct(strukt) => match strukt.field_list() {
-            // => self.<field>.hash(state);*
+            // => self.<field>.hash(state);
             Some(ast::FieldList::RecordFieldList(field_list)) => {
                 let mut stmts = vec![];
                 for field in field_list.fields() {
@@ -193,7 +307,7 @@ fn gen_hash_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
                 make::block_expr(stmts, None).indent(ast::edit::IndentLevel(1))
             }
 
-            // => self.<field_index>.hash(state);*
+            // => self.<field_index>.hash(state);
             Some(ast::FieldList::TupleFieldList(field_list)) => {
                 let mut stmts = vec![];
                 for (i, _) in field_list.fields().enumerate() {