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Remove broken redundant backtrace hint

When the compiler driver panics it attempts to show a hint about using
`RUST_BACKTRACE`. However, the logic is currently reversed to the hint
is only shown if `RUST_BACKTRACE` is *already* set:

```shell
> RUST_BACKTRACE=1 rustc /dev/null --crate-type proc-macro
error: internal compiler error: unexpected panic
...
note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'attempt to subtract with overflow', librustc_errors/emitter.rs:287:49
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

> RUST_BACKTRACE=0 rustc /dev/null --crate-type proc-macro
error: internal compiler error: unexpected panic
...
thread 'rustc' panicked at 'attempt to subtract with overflow', librustc_errors/emitter.rs:287:49
note: Run with `RUST_BACKTRACE=1` for a backtrace.
```

As the `panic` itself already has a working `RUST_BACKTRACE` hint just
remove the broken duplicate hint entirely.
This commit is contained in:
Ryan Cumming 2018-01-23 19:42:46 +11:00
parent 47a8eb7c4e
commit 5de8e040d2

View file

@ -1276,14 +1276,6 @@ pub fn monitor<F: FnOnce() + Send + 'static>(f: F) {
&note,
errors::Level::Note);
}
if match env::var_os("RUST_BACKTRACE") {
Some(val) => &val != "0",
None => false,
} {
handler.emit(&MultiSpan::new(),
"run with `RUST_BACKTRACE=1` for a backtrace",
errors::Level::Note);
}
eprintln!("{}", str::from_utf8(&data.lock().unwrap()).unwrap());
}