   Compiling cargo_capture_err v0.1.0 (/tmp/cargo_capture_compile_err)
error[E0277]: cannot add `&str` to `i32`
   --> src/lib.rs:2:7
    |
  2 |     a + "not a number"
    |       ^ no implementation for `i32 + &str`
    |
    = help: the trait `Add<&str>` is not implemented for `i32`
help: the following other types implement trait `Add<Rhs>`
   --> /home/john/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/arith.rs:99:9
    |
 99 |         impl const Add for $t {
    |         ^^^^^^^^^^^^^^^^^^^^^ `i32` implements `Add`
...
114 | add_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f16 f32 f64 f128 }
    | ---------------------------------------------------------------------------------- in this macro invocation
    |
   ::: /home/john/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/internal_macros.rs:22:9
    |
 22 |         impl const $imp<$u> for &$t {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ `&i32` implements `Add<i32>`
...
 33 |         impl const $imp<&$u> for $t {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ `i32` implements `Add<&i32>`
...
 44 |         impl const $imp<&$u> for &$t {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `&i32` implements `Add`
    = note: this error originates in the macro `add_impl` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0277`.
error: could not compile `cargo_capture_err` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `cargo_capture_err` (lib test) due to 1 previous error
