mirror of
https://github.com/rust-lang/rust.git
synced 2025-05-10 17:07:36 +00:00
df11395a55
Fix `#[derive(Default)]` on a generic `#[default]` enum adding unnecessary `Default` bounds
That is, given something like:
```rs
// #[default] on a generic enum does not add `Default` bounds to the type params.
#[derive(Default)]
enum MyOption<T> {
#[default]
None,
Some(T),
}
```
then `MyOption<T> : Default`_as currently implemented_ only holds when `T : Default`, as reported by ```@5225225``` [over Zulip](https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/.23.5Bderive.28Default.29.5D.20for.20enums.20with.20fields).
This is contrary to [what the accepted RFC proposes](https://rust-lang.github.io/rfcs/3107-derive-default-enum.html#generated-bounds) (_i.e._, that `T` be allowed not to be itself `Default`), and indeed seems to be a rather unnecessary limitation.
|
||
|---|---|---|
| .. | ||
| assert | ||
| deriving | ||
| format | ||
| format_foreign | ||
| asm.rs | ||
| assert.rs | ||
| cfg_accessible.rs | ||
| cfg_eval.rs | ||
| cfg.rs | ||
| cmdline_attrs.rs | ||
| compile_error.rs | ||
| concat_bytes.rs | ||
| concat_idents.rs | ||
| concat.rs | ||
| derive.rs | ||
| edition_panic.rs | ||
| env.rs | ||
| format_foreign.rs | ||
| format.rs | ||
| global_allocator.rs | ||
| lib.rs | ||
| log_syntax.rs | ||
| proc_macro_harness.rs | ||
| source_util.rs | ||
| standard_library_imports.rs | ||
| test_harness.rs | ||
| test.rs | ||
| trace_macros.rs | ||
| util.rs | ||