Cargo compile fails: error[E0658]: let...else statements are unstable

[anemovva]

When I try to compile the project with cargo build --release, the compile fails with the following error:
error[E0658]: let...else statements are unstable.

The full error is:
error[E0658]: let...else statements are unstable
--> src/hist_file.rs:16:5
|
16 | let Ok(histfile_buffer) = std::fs::File::open(&args.file) else { panic!("Please specify a valid histfile")};
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #87335 rust-lang/rust#87335 for more information
= help: add #![feature(let_else)] to the crate attributes to enable

For more information about this error, try rustc --explain E0658.
error: could not compile muc due to previous error /0.3s

I am using rustup version 1.25.1-2.

[nthnd]

I started coding this in rust 1.6.5. iirc that was when let ... else became stable. Compile it in a later version for it to work.