Substrate node template build errors and rustup version

Question

Once in a while, doing a rustup update will break the substrate node template, the challenge then becomes to identify the rustup release compatible with the latest node-template and downgrade. is this documented? or do we have to downgrade_rustup-test_compile_node_template-repeat every time? I am using the master branch of the substrate-node-template VS the latest rustup version, and I get the following error when doing a cargo check:

 Compiling substrate-wasm-builder v5.0.0-dev (https://github.com/paritytech/substrate.git?branch=polkadot-v1.0.0#948fbd2f)
error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: unresolved inference variable in outlives: ?8t
    --> /home/kazu/.cargo/git/checkouts/substrate-7e08433d4c370a21/948fbd2/primitives/runtime/src/traits.rs:1603:2
     |
1603 | /     fn validate(
1604 | |         &self,
1605 | |         who: &Self::AccountId,
1606 | |         call: &Self::Call,
1607 | |         info: &DispatchInfoOf<Self::Call>,
1608 | |         len: usize,
1609 | |     ) -> TransactionValidity {
     | |____________________________^
     |

This keeps happening even after downgrading and I don't know How far I have to downgrade to get it to work again (I stayed a while without doing any rustup update... ). If you know the rigtht rustup version, of better: a definitive way to solve this problem, please help. cordially, Kazunobu.

Edit 1: I just wanted to mention that the error first popped-up on github during the PR check process, which lead me to think that I had to update rustup: Huge mistake!!!

Answer 1

This is what I did to solve the problem locally. It still however remains an issue on github PRs:

1. completely remove rustup:

rustup self uninstall

sudo apt update

2. re-install (but no rustup update!!):

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

3. install rustup nightly:

rustup toolchain install nightly

rustup run nightly rustc --version

rustup default stable

4)Add wasm:

rustup target add wasm32-unknown-unknown --toolchain nightly

And done!! At least I can keep working locally, even if my PR appears faulty on github...