Merge #9924

9924: Fix gen debug for enums r=yoshuawuyts a=yoshuawuyts

Closes https://github.com/rust-analyzer/rust-analyzer/issues/9914. Thanks!

r? `@Veykril` 

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

crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs

@@ -302,6 +302,71 @@ impl core::fmt::Debug for Foo {
         }
     }
 }
+"#,
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_debug_tuple_enum() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: fmt
+#[derive(Debu$0g)]
+enum Foo {
+    Bar(usize, usize),
+    Baz,
+}
+"#,
+            r#"
+enum Foo {
+    Bar(usize, usize),
+    Baz,
+}
+
+impl core::fmt::Debug for Foo {
+    $0fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::Bar(arg0, arg1) => f.debug_tuple("Bar").field(arg0).field(arg1).finish(),
+            Self::Baz => write!(f, "Baz"),
+        }
+    }
+}
+"#,
+        )
+    }
+    #[test]
+    fn add_custom_impl_debug_record_enum() {
+        check_assist(
+            replace_derive_with_manual_impl,
+            r#"
+//- minicore: fmt
+#[derive(Debu$0g)]
+enum Foo {
+    Bar {
+        baz: usize,
+        qux: usize,
+    },
+    Baz,
+}
+"#,
+            r#"
+enum Foo {
+    Bar {
+        baz: usize,
+        qux: usize,
+    },
+    Baz,
+}
+
+impl core::fmt::Debug for Foo {
+    $0fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::Bar { baz, qux } => f.debug_struct("Bar").field("baz", baz).field("qux", qux).finish(),
+            Self::Baz => write!(f, "Baz"),
+        }
+    }
+}
 "#,
         )
     }

crates/ide_assists/src/utils/gen_trait_fn_body.rs

@@ -149,16 +149,90 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
             let mut arms = vec![];
             for variant in list.variants() {
                 let name = variant.name()?;
-                let variant_name =
+                let variant_name = make::ext::path_from_idents(["Self", &format!("{}", name)])?;
-                    make::path_pat(make::ext::path_from_idents(["Self", &format!("{}", name)])?);
-
                 let target = make::expr_path(make::ext::ident_path("f").into());
+
+                match variant.field_list() {
+                    Some(ast::FieldList::RecordFieldList(list)) => {
+                        // => f.debug_struct(name)
+                        let target = make::expr_path(make::ext::ident_path("f"));
+                        let method = make::name_ref("debug_struct");
+                        let struct_name = format!("\"{}\"", name);
+                        let args = make::arg_list(Some(make::expr_literal(&struct_name).into()));
+                        let mut expr = make::expr_method_call(target, method, args);
+
+                        let mut pats = vec![];
+                        for field in list.fields() {
+                            let field_name = field.name()?;
+
+                            // create a field pattern for use in `MyStruct { fields.. }`
+                            let pat = make::ident_pat(false, false, field_name.clone());
+                            pats.push(pat.into());
+
+                            // => <expr>.field("field_name", field)
+                            let method_name = make::name_ref("field");
+                            let name = make::expr_literal(&(format!("\"{}\"", field_name))).into();
+                            let path = &format!("{}", field_name);
+                            let path = make::expr_path(make::ext::ident_path(path));
+                            let args = make::arg_list(vec![name, path]);
+                            expr = make::expr_method_call(expr, method_name, args);
+                        }
+
+                        // => <expr>.finish()
+                        let method = make::name_ref("finish");
+                        let expr = make::expr_method_call(expr, method, make::arg_list(None));
+
+                        // => MyStruct { fields.. } => f.debug_struct("MyStruct")...finish(),
+                        let pat = make::record_pat(variant_name.clone(), pats.into_iter());
+                        arms.push(make::match_arm(Some(pat.into()), None, expr));
+                    }
+                    Some(ast::FieldList::TupleFieldList(list)) => {
+                        // => f.debug_tuple(name)
+                        let target = make::expr_path(make::ext::ident_path("f"));
+                        let method = make::name_ref("debug_tuple");
+                        let struct_name = format!("\"{}\"", name);
+                        let args = make::arg_list(Some(make::expr_literal(&struct_name).into()));
+                        let mut expr = make::expr_method_call(target, method, args);
+
+                        let mut pats = vec![];
+                        for (i, _) in list.fields().enumerate() {
+                            let name = format!("arg{}", i);
+
+                            // create a field pattern for use in `MyStruct(fields..)`
+                            let field_name = make::name(&name);
+                            let pat = make::ident_pat(false, false, field_name.clone());
+                            pats.push(pat.into());
+
+                            // => <expr>.field(field)
+                            let method_name = make::name_ref("field");
+                            let field_path = &format!("{}", name);
+                            let field_path = make::expr_path(make::ext::ident_path(field_path));
+                            let args = make::arg_list(vec![field_path]);
+                            expr = make::expr_method_call(expr, method_name, args);
+                        }
+
+                        // => <expr>.finish()
+                        let method = make::name_ref("finish");
+                        let expr = make::expr_method_call(expr, method, make::arg_list(None));
+
+                        // => MyStruct (fields..) => f.debug_tuple("MyStruct")...finish(),
+                        let pat = make::tuple_struct_pat(variant_name.clone(), pats.into_iter());
+                        arms.push(make::match_arm(Some(pat.into()), None, expr));
+                    }
+                    None => {
                         let fmt_string = make::expr_literal(&(format!("\"{}\"", name))).into();
-                let args = make::arg_list(vec![target, fmt_string]);
+                        let args = make::arg_list([target, fmt_string]);
                         let macro_name = make::expr_path(make::ext::ident_path("write"));
                         let macro_call = make::expr_macro_call(macro_name, args);
 
-                arms.push(make::match_arm(Some(variant_name.into()), None, macro_call.into()));
+                        let variant_name = make::path_pat(variant_name);
+                        arms.push(make::match_arm(
+                            Some(variant_name.into()),
+                            None,
+                            macro_call.into(),
+                        ));
+                    }
+                }
             }
 
             let match_target = make::expr_path(make::ext::ident_path("self"));
@@ -190,7 +264,7 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
                         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!("{}", name)).into();
-                        let args = make::arg_list(vec![f_name, f_path]);
+                        let args = make::arg_list([f_name, f_path]);
                         expr = make::expr_method_call(expr, make::name_ref("field"), args);
                     }
                     expr