[Pkg-rust-maintainers] Bug#1069798: rust-failure-derive - (build-)depends unsatisfiable.

[Peter Green]

Package: rust-failure-derive
Version: 0.1
Tags: trixie, sid
Severity: serious

rust-synstructure was recently updated to version 0.13.1

I tried bumping the dependency but that caused failures due to
mismatched versions of syn. Bumping the dependency on syn as well
resulted in.

> error[E0433]: failed to resolve: could not find `NestedMeta` in `syn`
>    --> src/lib.rs:129:18
>     |
> 129 |             syn::NestedMeta::Meta(syn::Meta::NameValue(ref nv)) if nv.path.is_ident("display") => {
>     |                  ^^^^^^^^^^ could not find `NestedMeta` in `syn`
>
> error[E0433]: failed to resolve: could not find `NestedMeta` in `syn`
>    --> src/lib.rs:140:18
>     |
> 140 |             syn::NestedMeta::Lit(syn::Lit::Int(ref i)) => {
>     |                  ^^^^^^^^^^ could not find `NestedMeta` in `syn`
>
> error[E0433]: failed to resolve: could not find `NestedMeta` in `syn`
>    --> src/lib.rs:144:18
>     |
> 144 |             syn::NestedMeta::Meta(syn::Meta::Path(ref path)) => {
>     |                  ^^^^^^^^^^ could not find `NestedMeta` in `syn`
>
> error[E0433]: failed to resolve: could not find `NestedMeta` in `syn`
>    --> src/lib.rs:252:39
>     |
> 252 |                         if let &&syn::NestedMeta::Meta(syn::Meta::Path(ref path)) = pair {
>     |                                       ^^^^^^^^^^ could not find `NestedMeta` in `syn`
>
> error[E0609]: no field `nested` on type `MetaList`
>    --> src/lib.rs:121:16
>     |
> 121 |         if msg.nested.is_empty() {
>     |                ^^^^^^ unknown field
>     |
>     = note: available fields are: `path`, `delimiter`, `tokens`
>
> error[E0609]: no field `nested` on type `MetaList`
>    --> src/lib.rs:128:39
>     |
> 128 |         let format_string = match msg.nested[0] {
>     |                                       ^^^^^^ unknown field
>     |
>     = note: available fields are: `path`, `delimiter`, `tokens`
>
> error[E0609]: no field `lit` on type `&MetaNameValue`
>    --> src/lib.rs:130:20
>     |
> 130 |                 nv.lit.clone()
>     |                    ^^^ unknown field
>     |
>     = note: available fields are: `path`, `eq_token`, `value`
>
> error[E0609]: no field `nested` on type `MetaList`
>    --> src/lib.rs:139:24
>     |
> 139 |         let args = msg.nested.iter().skip(1).map(|arg| match *arg {
>     |                        ^^^^^^ unknown field
>     |
>     = note: available fields are: `path`, `delimiter`, `tokens`
>
> error[E0599]: no method named `parse_meta` found for reference `&Attribute` in the current scope
>    --> src/lib.rs:202:32
>     |
> 202 |         if let Ok(meta) = attr.parse_meta() {
>     |                                ^^^^^^^^^^ help: there is a method with a similar name: `parse_nested_meta`
>
> error[E0599]: no method named `parse_meta` found for reference `&Attribute` in the current scope
>    --> src/lib.rs:242:32
>     |
> 242 |         if let Ok(meta) = attr.parse_meta() {
>     |                                ^^^^^^^^^^ help: there is a method with a similar name: `parse_nested_meta`
>
> error[E0609]: no field `nested` on type `&MetaList`
>    --> src/lib.rs:251:50
>     |
> 251 |                     if let Some(ref pair) = list.nested.first() {
>     |                                                  ^^^^^^ unknown field
>     |
>     = note: available fields are: `path`, `delimiter`, `tokens`

rust-failure has long been deprecated upstream, and rdeps have been gradually migrating away.
Looking at the remaining list of rdeps I see.

rust-assert-cli - no rdeps
rust-bendy - no rdeps
rust-coreutils - already broken and scheduled for autoremoval from testing soon
rust-distro-info - upstream has a patch switching to anyhow but hasn't yet included it in a release, only rdep is lintian-brush which is not in testing and already has a FTBFS bug.
rust-exitfailure - no rdeps
rust-include-dir-impl - no rdeps
rust-mdl - no rdeps
rust-rspotify - already broken and not in testing
rust-rustc-cfg - I have uploaded a new version of this that no longer depends on failure, and updated the rdeps to use it.