Check for literals as println! args

[mrecachinas]

Addresses #2480

[oli-obk]

This looks very clean, nice. Just a nit due to recent changes in our system.

Could you also add a test that ensures that println!("foo: {}", env!("BAR")); does not lint?

[oli-obk]

We're deprecating the use of this macro. Please use declare_clippy_lint together with the nursery group

[mrecachinas]

This is fixed in 511aa65.

[mrecachinas]

Good catch on the println!("foo: {}", env!("BAR")); -- it does throw the warning. I'll take a look at that and modify to use the declare_clippy_lint.

Currently running into some weirdness when running update_all_references.sh. It's modifying tests/ui/print.rs, tests/ui/print_with_newline.rs, and tests/ui/format.rs even with #![allow(print_literal)].

[oli-obk]

Sometimes you need to rerun all tests, run the script, run tests again, run the script before the update script catches on. This also happens inside rustc... no clue what's exactly happening.

[oli-obk]

You can probably fix the env! issue with very targetted in_macro calls. Not sure how that'll work, since println is also a macro. But technically the args should not be inside a macro expansion

[mrecachinas]

Yeah, looked like things were out of sync. A cargo clean seemed to do the trick.

[mrecachinas]

Do you think this should be pulled out of print.rs or run as an EarlyLintPass? I'm not seeing any indicator of a macro call (in this case to env!). On second thought, I don't think an EarlyLintPass would expand print! or println!.

In the test println!("foo: {}", env!("BAR")); (after setting BAR=test), I'm just seeing the value of $BAR (which in my case is the string "test")

[oli-obk]

Ah, thanks for investigating. Can you just list this issue under the downsides of the lint? It's fine to have this weird corner case imo

[mrecachinas]

Sounds good. I added the test-case and added the issue to "Known Problems."

Let me know if there's anything else you'd like to see in this.

[mrecachinas]

To make the tests reproducible (on all platforms) (and without explicitly setting an environment var), I removed the test with the env!. I suppose a format! would accomplish the same thing. Let me know if you want it added.

[oli-obk]

Nope, this is fine as it is. Thanks