Error expanding macro recursively at caret: `$crate` cannot come from `SyntaxContextId::ROOT`

When trying to expand a proc_macro, most often the rust-analyzer errs with:

What's odd is that it doesn't always happen. Sometimes I can rebuild dependencies in our workspace, restart the LSP server, and it'll work. I also don't use $crate myself, though #[tokio::test], assert_eq!(), and some other macros may that end up getting expanded recursively.

This most often happens when I make a change to my crate e.g., minor bug fix or small behavior change as I tweak what it does for this in-development feature, and then try to expand the macro. rust-analyzer is rebuilding dependencies, but I've suspected it's a cached build output issue somehow.

rust-analyzer version: (eg. output of "rust-analyzer: Show RA Version" command, accessible in VSCode via Ctrl/⌘+Shift+P)

0.3.2212-standalone

rustc version: (eg. output of rustc -V)

rustc 1.80.0 (051478957 2024-07-21) (pinned via rust-toolchain.toml)

editor or extension: (eg. VSCode, Vim, Emacs, etc. For VSCode users, specify your extension version; for users of other editors, provide the distribution if applicable)

VSCode rust-lang.rust-analyzer extension version v0.3.2212

relevant settings: (eg. client settings, or environment variables like CARGO, RUSTC, RUSTUP_HOME or CARGO_HOME)

Only a few relative things come to mind:

• rust-toolchain.toml pins channel to 1.80.0
• .vscode/settings.json sets "rust-analyzer.cargo.features": "all" and "rust-analyzer.check.command": "clippy".

repository link (if public, optional): (eg. rust-analyzer)

• proc_macro: https://github.com/heaths/azure-sdk-for-rust/blob/09c9a45b1a267f304d34a55567e2935633f60cbe/sdk/core/azure_core_test_macros/src/test.rs
• use case: https://github.com/heaths/azure-sdk-for-rust/blob/09c9a45b1a267f304d34a55567e2935633f60cbe/sdk/cosmos/azure_data_cosmos/tests/cosmos_containers.rs#L19

code snippet to reproduce:

See links directly above.

Start with the proc_macro at sdk/core/azure_core_test_macros/src/test.rs and its use in sdk/cosmos/azure_data_cosmos/tests/cosmos_containers.rs#L19, using the pinned rust-toolchain.toml and the reported VSCode settings. Reproduce the recursive expansion failure after a dependency rebuild, then trace the relevant rust-analyzer macro-expansion path. Done means the failure has a reliable reproduction and its behavior is covered by a verified fix.