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Two different versions of a crate interacting leads to unhelpful error messages #22750
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This bit me today with |
Related, its also annoying if only crate local paths get emitted, like in backtraces. We need a way for crates to identify themself uniquely, and not just by an identifier. Maybe a scheme like |
I was bitten by this too. Kimundi: Agreed for the need to unique identification. But then again, in some cases the local path tells more directly where the problem is. I wonder if there are cases where path is better and cases where a hash is better. Or maybe some kind of hybrid: If version information from cargo is available, use that. If not, if version control information is available, use commit SSH, and if no other information exists, use a path...? |
Nominating for high priority. I think this is one of the main pain points people have when using cargo, and one of the major reasons for people complaining about cargo allowing multiple versions of a crate. It's usually easy to identify once you've seen it a few times, but it is a horribly confusing and annoying experience. (Tagged with both compiler and tools since cargo presumably plays into this, but this is probably most relevant to the compiler subteam.) @golddranks: the question of connecting semantically relevant info to crates is discussed a little in the issue. I think the best plan would external tools to pass in arbitrary strings connected to each crate, defaulting to the path, meaning rustc doesn't have to actually understand anything, just print strings (the compiler already has an |
I've also seen an increasing number of IRC questions about this.
|
I'll take a crack at this |
I think at the very least, for mismatched type and unimplemented trait errors, if we detect a crate mismatch, we should mention it. Any other such errors? |
Mismatched type is the big one. Being able to understand this would also help Rustdoc a lot, I think there are bugs open. (That way, we could know if something is a re-export or not) |
…m two different crate of the same name (rust-lang#22750)
Partially fixes #22750 I'll write a test for this when I figure out how to. r? @eddyb cc @steveklabnik
No no no github, I said "partial fix" |
Anyway, #28300 fixes the error when there's a type mismatch. "Can't find trait" will be a tad trickier |
I had a corner-case posted on Reddit that was even more confusing:
I was using Hyper with the latest cookie crate. I did it because even though 'hyper' depends on 'cookie=0.1.21' or somesuch, I couldn't use 'cookie' on my program. I'll suggest a change on cargo if it doesn't yet exist. |
Yeah, this should be fixed but the just-landed PR. |
triage: P-medium -- we think that the most important cases here have been covered. If this issue continues to arise frequently on IRC, we could bump up the priority to high. |
I would have loved to get a "Perhaps two different versions of crate |
I was bitten by this today. Since |
@robinmoussu I just noticed |
…imulacrum Add note for mismatched types because of circular dependencies If you have crate A with a dependency on crate B, and crate B with a dev-dependency on A, then you might see "mismatched types" errors on types that seem to be equal. This PR adds a note that explains that the types are different, because crate B is compiled twice, one time with `cfg(test)` and one time without. I haven't found a good way to create circular dependencies in UI tests, so I abused the incremental tests instead. As a bonus, incremental tests support "cpass" now. related to rust-lang#22750
I was helping someone troubleshoot a subcase of this and followed up with https://internals.rust-lang.org/t/better-error-when-trait-not-implemented-because-of-different-crate-version/18808. #73560 seems to do a good job of covering the case I ran into and it looks like a subcase of this issue. |
When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
…fee1-dead On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
…<try> On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
…r=fee1-dead On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
…r=fee1-dead On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
…r=fee1-dead On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
…r=fee1-dead On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
Rollup merge of rust-lang#124944 - estebank:multiple-crate-versions, r=fee1-dead On trait bound mismatch, detect multiple crate versions in dep tree When encountering an E0277, if the type and the trait both come from a crate with the same name but different crate number, we explain that there are multiple crate versions in the dependency tree. If there's a type that fulfills the bound, and it has the same name as the passed in type and has the same crate name, we explain that the same type in two different versions of the same crate *are different*. ``` error[E0277]: the trait bound `Type: dependency::Trait` is not satisfied --> src/main.rs:4:18 | 4 | do_something(Type); | ------------ ^^^^ the trait `dependency::Trait` is not implemented for `Type` | | | required by a bound introduced by this call | help: you have multiple different versions of crate `dependency` in your dependency graph --> src/main.rs:1:5 | 1 | use bar::do_something; | ^^^ one version of crate `dependency` is used here, as a dependency of crate `bar` 2 | use dependency::Type; | ^^^^^^^^^^ one version of crate `dependency` is used here, as a direct dependency of the current crate note: two types coming from two different versions of the same crate are different types even if they look the same --> /home/gh-estebank/crate_versions/baz-2/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type doesn't implement the required trait | ::: /home/gh-estebank/crate_versions/baz/src/lib.rs:1:1 | 1 | pub struct Type; | ^^^^^^^^^^^^^^^ this type implements the required trait 2 | pub trait Trait {} | --------------- this is the required trait note: required by a bound in `bar::do_something` --> /home/gh-estebank/crate_versions/baz/src/lib.rs:4:24 | 4 | pub fn do_something<X: Trait>(_: X) {} | ^^^^^ required by this bound in `do_something` ``` Address rust-lang#22750.
https://github.com/huonw/bad-error-messages-a contains a crate
a
. https://github.com/huonw/bad-error-messages-bc contains two crates,b
andc
.a
contains a traitFoo
and a functiontest
that requires that trait.b
depends on a specific revision (8b532f5, not the HEAD) ofa
and contains a typeBar
that implementsa::Foo
.c
depends ona
's HEAD (happens to be 84cfe230) andb
, and tries to useb::Bar
witha::test
.c
fails to compile despiteBar
"clearly" implementingFoo
... it's even displayed in the docs!Cloning https://github.com/huonw/bad-error-messages-bc and running
cargo build
in the root (which isc
) givesThere's no indication of the fundamental problem from either
rustdoc
orrustc
: that there's two different versions ofa
being used, meaninga#84cfe230::Foo
anda#8b532f5::Foo
are different.Bar
only implements the latter, but inc
, the namea
refers toa#84cfe230
soa::test(...)
requires the former. (Usingname#rev
to represent the crate with that version.)There is an indication of the difference in the example above, since
a
is compiled twice, but that comes fromcargo
, notrustc
. This issue is focusing on the fact thatrustc
itself does not give helpful errors and/or allow tools like cargo to control those errors.It would be nice if rustc:
foo#0.2.3
instead of the filepath/name"note: there's multiple versions of crate
...in use"
: along with a listing of the possibilities.(NB. I've used
cargo
to construct this example because it is the easiest way I can get two different versions of a crate. This appears in rust-lang/rust's makefiles too, where thestd
test runner is called "std" internally, but links against another crate called "std", i.e. the conventional standard library.)The text was updated successfully, but these errors were encountered: