Rollup merge of #64678 - tomtau:fix/no-std-error, r=matthewjasper

added more context for duplicate lang item errors (fixes #60561)

Some more information about #60561 -- these errors are pretty common when one works in restrictive environments with `no_std` or customized `std`, but they don't provide much context for debugging, as any transitive dependency could have brought in `std` crate. With that, currently, one needs to use something like `cargo tree` and investigate transitive dependencies one by one.

It'll be more helpful to know at least the crate that uses `std` (which `cargo tree` doesn't show) to pin down this investigation when debugging.

I'm not sure what the best way to get this context is inside rustc internals (I'm new to them). I found that `all_crate_nums` query returns the crates in some dependency order, so printing out the name of the preceding crate seems to do the trick. But I welcome suggestions if this can be done in a better way.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/ui/panic-handler/panic-handler-std.stderr b/src/test/ui/panic-handler/panic-handler-std.stderr
index 32240311116..e6d24348ca8 100644
--- a/src/test/ui/panic-handler/panic-handler-std.stderr
+++ b/src/test/ui/panic-handler/panic-handler-std.stderr
@@ -6,7 +6,7 @@ LL | |     loop {}
 LL | | }
    | |_^
    |
-   = note: first defined in crate `std`.
+   = note: first defined in crate `std` (which `panic_handler_std` depends on).
 
 error: argument should be `&PanicInfo`
   --> $DIR/panic-handler-std.rs:7:16