unsatisfyable HKL error message prints broken bound (`for<'b> 'b : `)

[oli-obk]

the full error is

error[E0279]: the requirement `for<'b> 'b : ` is not satisfied (`expected bound lifetime parameter 'b, found concrete lifetime`)
 --> <anon>:2:5
  |
2 |     test::<FooS>(&mut 42);
  |     ^^^^^^^^^^^^
  |
  = note: required because of the requirements on the impl of `for<'b> Foo<'b>` for `FooS<'_>`
  = note: required by `test`

reproducible example on stable, beta and nightly:

fn main() {
    test::<FooS>(&mut 42);
}

trait Foo<'a> {}

struct FooS<'a> {
    data: &'a mut u32,
}

impl<'a, 'b: 'a> Foo<'b> for FooS<'a> {}

fn test<'a, F>(data: &'a mut u32) where F: for<'b> Foo<'b> {}

[kennytm]

Another program which produces similar message:

trait R<'a, 's: 'a> {}

impl<'a, 's: 'a> R<'a, 's> for u32 {}

struct S<X: for<'a> R<'a, 'static>>(X);

fn f(x: S<u32>) {}

Error:

error: main function not found

error[E0279]: the requirement `for<'a>  : 'a` is not satisfied (`expected bound lifetime parameter 'a, found concrete lifetime`)
 --> 1.rs:7:1
  |
7 | fn f(x: S<u32>) {}
  | ^^^^^^^^^^^^^^^^^^
  |
  = note: required because of the requirements on the impl of `for<'a> R<'a, 'static>` for `u32`
  = note: required by `S`

error: aborting due to previous error

BTW,

• E0279 is not found in the error index (Add error explanations for all error codes #32777)
• I think this piece of code should compile, since u32 does implement R<'a, 'static> for every 'a.

---

Version:

rustc 1.18.0-nightly (3b5754e5c 2017-04-10)
binary: rustc
commit-hash: 3b5754e5ce73d24c6684b3ed0c68a557dfdd2f52
commit-date: 2017-04-10
host: x86_64-apple-darwin
release: 1.18.0-nightly
LLVM version: 3.9

[estebank]

Current output:

error: implementation of `Foo` is not general enough
 --> src/main.rs:2:5
  |
2 |     test::<FooS>(&mut 42);
  |     ^^^^^^^^^^^^
  |
  = note: Due to a where-clause on `test`,
  = note: `FooS<'_>` must implement `Foo<'0>`, for any lifetime `'0`
  = note: but `FooS<'_>` actually implements `Foo<'1>`, for some specific lifetime `'1`

---

The case in the comment now compiles.

---

Working on a PR to make the output:

error: implementation of `Foo` is not general enough
  --> file.rs:2:5
   |
2  |     test::<FooS>(&mut 42);
   |     ^^^^^^^^^^^^
...
13 | fn test<'a, F>(data: &'a mut u32) where F: for<'b> Foo<'b> {}
   | ------------------------------------------------------------- due to a where-clause on `test`...
   |
   = note: ...`FooS<'_>` must implement `Foo<'0>`, for any lifetime `'0`...
   = note: ...but `FooS<'_>` actually implements `Foo<'1>`, for some specific lifetime `'1`

[onlineSoftwareDevOK]

Is it possible to reproduce E0279 using Rust stable nowadays? I am writing documentation for that error. Every code snippet which used to throw that error now returns implementation of X is not general enough

[onlineSoftwareDevOK]

Is it possible to reproduce E0279 using Rust stable nowadays? I am writing documentation for that error. Every code snippet which used to throw that error now returns implementation of X is not general enough

@estebank Do you know this?