`rustc -Wall` to show all possible warnings

[mcandre]

It would be nice if rustc -Wall turned on all warnings, like how other compilers work.

[thestinger]

At least with clang and gcc, -Wall doesn't turn on all the warnings. I don't think turning all on the warnings is ever going to be useful because lots are going to be very domain specific (ones like heap-memory already are).

clang has a fairly useless -Weverything to turn on all warnings, and -Wmost to turn on all those included by -Wall, -Wextra and also many more that are considered to be useful. Rust already has all the warnings viewed as useful and not too subjective on by default.

[mcandre]

@thestinger Oh, wow! Thanks for the detailed, thoughtful response. I'll definitely look into each of those options.

[thestinger]

(FWIW the warnings are listed in -W help and are almost all on by default)

[sanmai-NL]

I think there should be a catch-all lint group, that objectively enables all lints. Whenever programmers decide subjectively to allow lints in some instances, they may then do that on a case-by-case basis. And if an implemented lint simply does not make sense at all then it should be improved/removed. The existing lint group warnings apparently does not include all built-in lint groups, contrary to the output of rustc -W help (rustc 1.19.0-nightly (01951a61a 2017-05-20)):

Lint groups provided by rustc:

                   name  sub-lints
                   ----  ---------
               warnings  all built-in lints
              bad-style  non-camel-case-types, non-snake-case, non-upper-case-globals
    future-incompatible  private-in-public, inaccessible-extern-crate, invalid-type-param-default, super-or-self-in-global-path, illegal-floating-point-constant-pattern, illegal-floating-point-literal-pattern, illegal-struct-or-enum-constant-pattern, hr-lifetime-in-assoc-type, lifetime-underscore, resolve-trait-on-defaulted-unit, safe-extern-statics, patterns-in-fns-without-body, extra-requirement-in-impl, legacy-directory-ownership, legacy-imports, legacy-constructor-visibility, missing-fragment-specifier, anonymous-parameters
                 unused  unused-imports, unused-variables, unused-assignments, dead-code, unused-mut, unreachable-code, unreachable-patterns, unused-must-use, unused-unsafe, path-statements, unused-attributes, unused-macros

@Mark-Simulacrum can this issue be reopened?

[Mark-Simulacrum]

Reopening.

However, I think we shouldn't have any sort of "enable all lints" option; rustc's lints are already all intended to have no or very few false positives (and as such are enabled by default where that makes sense). Could you talk about which specific lints are missing from the default warnings built-in list? I'm not personally aware of any. I'm also somewhat concerned that a -Wall or similar option would be confusing to some extent because "all" wouldn't include clippy lints (and probably can't, or at least not easily -- though I don't know the details here).

[Phlosioneer]

Issue triage:

rustc -W help no longer prints warnings all built-in lints, so that was fixed at some point. (it now prints warnings all lints that are set to issue warnings)

I think it might be useful to have a message explaining why -Wall doesn't exist, point the user toward -W help to see all available errors, and suggest adding a #![warn(unused)] for a more thorough lint check. This would help beginners coming from other languages to 1) understand that most useful warnings are turned on by default, 2) tell the user that -W help exists, and 3) show the user that warnings can be controlled from inside the source code, rather than the command line.

If there's interest in doing this, I could make a PR.