This is an MCVE for reproducing the bug when the code is not shown which actually causes errors. The errors itselves are shown correctly. The output looks as this:
Compiling bug v0.1.0 (/home/rust/src/bug)
error[E0308]: mismatched types
|
= note: expected type `std::string::String`
found type `&'static str`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0308`.
error: Could not compile `bug`.
To learn more, run the command again with --verbose.
After bisection it was evident that the problem is seen on all nightly compilers up to these days, starting from nightly-2019-04-15. The versions before have not been tested as serde framework can't be compiled on earlier versions of the compiler. However, if it only had been possible to set the serde version less than 1.0.99, we would have been able to bisect further.
More information can be found on the bug page.