Stop mentioning internal lang items in no_std binary errors

When writing a no_std binary, you'll be greeted with nonsensical errors
mentioning lang items like eh_personality and start. That's pretty bad
because it makes you think that you need to define them somewhere! But
oh no, now you're getting the `internal_features` lint telling you that
you shouldn't use them! But you need a no_std binary! What now?

No problem! Writing a no_std binary is super easy. Just use panic=abort
and supply your own platform specific entrypoint symbol (like `main`)
and you're good to go. Would be nice if the compiler told you that,
right?

This makes it so that it does do that.

1 files changed, 6 insertions, 0 deletions

diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index d934e959a41..cf3c7cc4ace 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -813,6 +813,12 @@ pub struct UnknownExternLangItem {
 pub struct MissingPanicHandler;
 
 #[derive(Diagnostic)]
+#[diag(passes_panic_unwind_without_std)]
+#[help]
+#[note]
+pub struct PanicUnwindWithoutStd;
+
+#[derive(Diagnostic)]
 #[diag(passes_missing_lang_item)]
 #[note]
 #[help]