From cdc3d701cb4ff37e9d0c96c1c68b2e8789c19441 Mon Sep 17 00:00:00 2001 From: León Orell Valerian Liehr Date: Fri, 18 Jul 2025 12:24:56 +0200 Subject: Don't reject *multiple* relaxed bounds, reject *duplicate* ones. Having multiple relaxed bounds like `?Sized + ?Iterator` is actually *fine*. We actually want to reject *duplicate* relaxed bounds like `?Sized + ?Sized` because these most certainly represent a user error. Note that this doesn't mean that we accept more code because a bound like `?Iterator` is still invalid as it's not relaxing a *default* trait and the only way to define / use more default bounds is under the experimental and internal feature `more_maybe_bounds` plus `lang_items` plus unstable flag `-Zexperimental-default-bounds` (historical context: for the longest time, bounds like `?Iterator` were actually allowed and lead to a hard warning). Ultimately, this simply *reframes* the diagnostic. The scope of `more_maybe_bounds` / `-Zexperimental-default-bounds` remains unchanged as well. --- compiler/rustc_error_codes/src/error_codes/E0203.md | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'compiler/rustc_error_codes/src') diff --git a/compiler/rustc_error_codes/src/error_codes/E0203.md b/compiler/rustc_error_codes/src/error_codes/E0203.md index 1edb519275f..a4dceedbf1f 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0203.md +++ b/compiler/rustc_error_codes/src/error_codes/E0203.md @@ -1,15 +1,15 @@ -Having multiple relaxed default bounds is unsupported. +Having duplicate relaxed default bounds is unsupported. Erroneous code example: ```compile_fail,E0203 -struct Bad{ - inner: T +struct Bad{ + inner: T, } ``` -Here the type `T` cannot have a relaxed bound for multiple default traits -(`Sized` and `Send`). This can be fixed by only using one relaxed bound. +Here the type parameter `T` cannot have duplicate relaxed bounds for default +trait `Sized`. This can be fixed by only using one relaxed bound: ``` struct Good{ -- cgit 1.4.1-3-g733a5