Cargo-contract forcibly calls nightly-2022-06-30 regardless of specified toolchain

Question

I am experiencing an issue when using cargo-contract (version 1.5.1) to build a project (command: cargo +nightly contract build). The specified toolchain is not being recognized, and the process is forcibly calling nightly-2022-06-30 instead.

This occurs on both my M2 MacOS and Ubuntu (within the Windows11 WSL environment), suggesting that the problem is likely not device-dependent. I have followed the installation instructions as outlined in Astar Doc's Ink! Environment (https://docs.astar.network/docs/build/environment/ink_environment/).

The issue surfaces when building a flipper created by cargo contract new flipper. Interestingly, the problem does not occur when I install cargo-contract V2, suggesting that the issue might specifically be with V1.5.1.

There are no elements that could potentially influence the toolchain specification (such as environment variables or specification via the rust-toolchain file). Even after uninstalling nightly-2022-06-30 using rustup toolchain uninstall, the process still attempts to call this version.

Here is the corresponding log:

yasuyasu@mocomocha:~/astar/flipper$ cargo +nightly contract build
2023-05-13T12:50:30.989598Z  INFO cargo_contract::crate_metadata: Fetching cargo metadata for Cargo.toml
2023-05-13T12:50:31.050626Z  INFO cargo_contract::util: Invoking cargo: "/home/yasuyasu/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo" "tree" "-i" "parity-scale-codec" "--duplicates"
2023-05-13T12:50:31.070036Z  INFO cargo_contract::util: Invoking cargo: "/home/yasuyasu/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo" "tree" "-i" "scale-info" "--duplicates"
2023-05-13T12:50:31.088857Z  INFO cargo_contract::cmd::build: Contract version: Version { major: 3, minor: 4, patch: 0 }
 [1/5] Checking ink! linting rules
2023-05-13T12:50:31.113119Z  INFO cargo_contract::util: Invoking cargo: cd "/home/yasuyasu/astar/flipper" && DYLINT_LIBRARY_PATH="/tmp/cargo-contract-dylint_CAz4e7" "/home/yasuyasu/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo" "dylint" "--lib" "ink_linting" "--manifest-path=/home/yasuyasu/astar/flipper/Cargo.toml"
Checking with toolchain `nightly-2022-06-30-x86_64-unknown-linux-gnu`
    Checking scale-info v2.6.0
error[E0658]: `let...else` statements are unstable
   --> /home/yasuyasu/.cargo/registry/src/github.com-1ecc6299db9ec823/scale-info-2.6.0/src/portable.rs:130:17
    |
130 | /                 let Some(ty) = &param.ty else {
131 | |                     continue
132 | |                 };
    | |__________________^
    |
    = note: see issue #87335 <https://github.com/rust-lang/rust/issues/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 `scale-info` due to previous error
Error: Compilation failed with toolchain `nightly-2022-06-30-x86_64-unknown-linux-gnu`

Caused by:
    command failed: CLIPPY_DISABLE_DOCS_LINKS="null" DYLINT_LIBS="[\"/tmp/cargo-contract-dylint_CAz4e7/libink_linting@nightly-2022-06-30-x86_64-unknown-linux-gnu.so\"]" RUSTC_WORKSPACE_WRAPPER="/home/yasuyasu/.dylint_drivers/nightly-2022-06-30-x86_64-unknown-linux-gnu/dylint-driver" RUSTUP_TOOLCHAIN="nightly-2022-06-30-x86_64-unknown-linux-gnu" "cargo" "check" "--target-dir" "/home/yasuyasu/astar/flipper/target/dylint/target/nightly-2022-06-30-x86_64-unknown-linux-gnu" "--manifest-path" "/home/yasuyasu/astar/flipper/Cargo.toml"
ERROR: `cd "/home/yasuyasu/astar/flipper" && DYLINT_LIBRARY_PATH="/tmp/cargo-contract-dylint_CAz4e7" "/home/yasuyasu/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo" "dylint" "--lib" "ink_linting" "--manifest-path=/home/yasuyasu/astar/flipper/Cargo.toml"` failed with exit code: Some(1)
yasuyasu@mocomocha:~/astar/flipper$