Following the instructions at (https://bruno.id/preparation-for-the-substrate-workshop/) until I received a build error, executing the instructions under the 'Error' heading, I received the following error E0635.enter image description here

I executed: rustc --explain E0635 which provided the following output: enter image description here

My ubuntu and rust toochain versions are as follows:enter image description here

enter image description here

How might I fix this?

6 Answers 6

rustup default nightly-2022-07-24 && rustup target add wasm32-unknown-unknown

IMO, it's always good to follow the latest Polkadot release CI's Rust toolchain.



I got the same issue today and rustup update doesn't work. And I came to an idea.

rm -fr target Cargo.lock
cargo check

that's it. But anyone know what's the cause of it?


For those who are having the same problem since version 1.72.0, you need to do the same: pause updates of nightly rust. You can do this by editing rust-toolchain.toml file:

channel = "nightly-2023-06-15"

I got the same issue, rustup default stable solved it


The tracking issue on the rust github is this: https://github.com/rust-lang/rust/issues/113152

In short, removing Cargo.lock and recompiling should fix this.


You need to update your nightly. You are using one from 2020, that is quite old. Running rustup update should do it.

  • I updated, thanks! I'm still getting some build errors, but they are new errors. Progress! =)
    – Brian
    Commented Oct 19, 2022 at 0:59

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