lalrpop triggers a future-incompat warning on Rust 1.69

[kleinesfilmroellchen]

When compiling a project including lalrpop with rustc 1.69.0-nightly (c8e6a9e8b 2023-01-23), a warning about future incompatibility is issued. The full report given by cargo report future-incompatibilities --id 10 --package lalrpop@0.19.8 is:

The following warnings were discovered during the build. These warnings are an
indication that the packages contain code that will become an error in a
future release of Rust. These warnings typically cover changes to close
soundness problems, unintended or undocumented behavior, or critical problems
that cannot be fixed in a backwards-compatible fashion, and are not expected
to be in wide use.

Each warning should contain a link for more information on what the warning
means and how to resolve it.


To solve this problem, you can try the following approaches:


- If the issue is not solved by updating the dependencies, a fix has to be
implemented by those dependencies. You can help with that by notifying the
maintainers of this problem (e.g. by creating a bug report) or by proposing a
fix to the maintainers (e.g. by creating a pull request):

  - lalrpop@0.19.8
  - Repository: https://github.com/lalrpop/lalrpop
  - Detailed warning command: `cargo report future-incompatibilities --id 10 --package lalrpop@0.19.8`

- If waiting for an upstream fix is not an option, you can use the `[patch]`
section in `Cargo.toml` to use your own version of the dependency. For more
information, see:
https://doc.rust-lang.org/cargo/reference/overriding-dependencies.html#the-patch-section
        
The package `lalrpop v0.19.8` currently triggers the following future incompatibility lints:
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |           });
>     |             ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\prevalidate\mod.rs:158:42
>     |
> 158 |   ...                   _ => return_err!(
>     |  ____________________________-
> 159 | | ...                       annotation.id_span,
> 160 | | ...                       r#"`cfg` annotations must have a `feature = "my_feature" argument"#
> 161 | | ...                   ),
>     | |_______________________- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\prevalidate\mod.rs:241:40
>     |
> 241 | ...) => return_err!(ann_prec.id_span, "invalid argument `{}` for precedence annotation, expected `{}`", name, precedence::LVL_ARG),
>     |         -------------------------------------------------------------------------------------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\prevalidate\mod.rs:242:29
>     |
> 242 |                     None => return_err!(ann_prec.id_span, "missing argument for precedence annotation, expected `{}`", precedence::LVL_ARG),
>     |                             --------------------------------------------------------------------------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\prevalidate\mod.rs:253:40
>     |
> 253 | ...=> return_err!(ann_assoc.id_span, "invalid argument `{}` for associativity annotation, expected `{}`", name, precedence::SIDE_ARG),
>     |       ------------------------------------------------------------------------------------------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\prevalidate\mod.rs:254:29
>     |
> 254 | ...one => return_err!(ann_assoc.id_span, "missing argument for associativity annotation, expected `{}`", precedence::SIDE_ARG),
>     |           -------------------------------------------------------------------------------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |           });
>     |             ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\resolve\mod.rs:228:76
>     |
> 228 |                       Def::Nonterminal(0) | Def::Terminal | Def::MacroArg => return_err!(
>     |  ____________________________________________________________________________-
> 229 | |                         symbol.span,
> 230 | |                         "`{}` is a {}, not a macro",
> 231 | |                         msym.name,
> 232 | |                         def.description()
> 233 | |                     ),
>     | |_____________________- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\resolve\mod.rs:273:36
>     |
> 273 |             Def::Nonterminal(_) => return_err!(symbol.span, "`{}` is a macro", id),
>     |                                    ----------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\resolve\mod.rs:281:21
>     |
> 281 |             None => return_err!(span, "no definition found for `{}`", id),
>     |                     ----------------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\macro_expand\mod.rs:167:21
>     |
> 167 |             None => return_err!(span, "no macro definition found for `{}`", msym.name),
>     |                     ------------------------------------------------------------------ in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |         });
>     |           ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\macro_expand\mod.rs:320:25
>     |
> 320 |             Err(err) => return_err!(span, "invalid regular expression `{}`: {}", regex, err),
>     |                         -------------------------------------------------------------------- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |           });
>     |             ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\macro_expand\mod.rs:398:21
>     |
> 398 | /                     return_err!(
> 399 | |                     span,
> 400 | |                     "named symbols like `{}:{}` are only allowed at the top-level of a nonterminal",
> 401 | |                     ex_id, ex_sym)
>     | |__________________________________- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: macro invocations at the end of a block are treated as expressions
>     = note: to ignore the value produced by the macro, add a semicolon after the invocation of `return_err`
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |           });
>     |             ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\token_check\mod.rs:366:13
>     |
> 366 | /             return_err!(
> 367 | |                 spans[literal],
> 368 | |                 "{} are not supported in regular expressions",
> 369 | |                 feature
> 370 | |             )
>     | |_____________- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: macro invocations at the end of a block are treated as expressions
>     = note: to ignore the value produced by the macro, add a semicolon after the invocation of `return_err`
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> warning: trailing semicolon in macro used in expression position
>    --> C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\mod.rs:22:11
>     |
> 22  |           });
>     |             ^
>     |
>    ::: C:\Users\USERNAME\.cargo\registry\src\github.com-1ecc6299db9ec823\lalrpop-0.19.8\src\normalize\token_check\mod.rs:376:13
>     |
> 376 | /             return_err!(
> 377 | |                 spans[literal0],
> 378 | |                 "ambiguity detected between the terminal `{}` and the terminal `{}`",
> 379 | |                 literal0,
> 380 | |                 literal1
> 381 | |             )
>     | |_____________- in this macro invocation
>     |
>     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>     = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>     = note: macro invocations at the end of a block are treated as expressions
>     = note: to ignore the value produced by the macro, add a semicolon after the invocation of `return_err`
>     = note: `#[allow(semicolon_in_expressions_from_macros)]` on by default
>     = note: this warning originates in the macro `return_err` (in Nightly builds, run with -Z macro-backtrace for more info)
> 

[ithinuel]

If my understanding is correct, this line in #703 should fix it : https://github.com/lalrpop/lalrpop/pull/703/files#diff-11d925fcd5e444d0d3113d95dc281c39582b84a3f7c13f5b103f6e0af85d91d4L22

[kleinesfilmroellchen]

Yes, that looks good!

[fanninpm]

@matklad do you want to look at the numerous PRs that want to fix this?

[youknowone]

A new version is released. Thank you for reporting!