cargo test gives bad advice when given invalid target

[xobs]

Problem

It is possible to run tests for various targets using cargo test --target [triple]. When given an invalid triple, cargo indicates the user should run --print target-list for help. However, this is not valid advice.

Steps

1. Run cargo test --target invalid-target
2. Run the suggested cargo test --print target-list

Possible Solution(s)

cargo should implement --print target-list, or the advice should be removed.

Notes

Output of cargo version: cargo 1.40.0 (bc8e4c8be 2019-11-22)

$ cargo test --target invalid-target
error: failed to run `rustc` to learn about target-specific information

Caused by:
  process didn't exit successfully: `rustc - --crate-name ___ --print=file-names --target invalid-target --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=cfg` (exit code: 1)
--- stderr
error: Error loading target specification: Could not find specification for target "invalid-target"
  |
  = help: Use `--print target-list` for a list of built-in targets


$ cargo test --print target-list
error: Found argument '--print' which wasn't expected, or isn't valid in this context

USAGE:
    cargo.exe test [OPTIONS] [TESTNAME] [-- <args>...]

For more information try --help
$
...

[lukaslueg]

This can be confusing but cctually cargo just prints what rustc is saying via stderr: run rustc --print target-list

[ehuss]

Yea, this message is printed by rustc, so I have moved this to the rust issue tracker.

It seems reasonable to me that it should include rustc before the --print flag, though maybe the diagnostic people have further thoughts.