Shebang requirement and cargo macro

[tgross35]

All the examples have the cargo shebang - is this a requirement to identify a cargo-script file? If so, presence of this shebang (or a fallback option like --as-cargo-script) could be used to indicate to rustc that it should ignore the special cargo! macro or attribute.

This would be an alternative to std containing the cargo macro, as mentioned here https://github.com/epage/cargo-script-mvs/blob/b31a41c43634acc8d2358811ba4706d1f3dff4fc/0000-cargo-script.md#embedded-manifest-format

Another more general option could be for rustc to gain a --ignore-macros option that, well, ignores macros. This would mean that it doesn't need any specific awareness of cargo-script. Additionally, it would open up other tools to doing in-source configuration in a similar way: which could be either good or bad.

[epage]

At the moment, shebang is not required. It might be useful for tools like rust-analyzer to pick up the role of these files. I have not looked too deeply into shebang detection but my gut says its a messy afair based on perl so I'd prefer for us to not make it a requirement. I also am considering cargo Cargo.toml support for complete consistency in where manifests are supported and that means the shebang isn't a complete tell.

[tgross35]

Fair enough, the idea just came up because I believe the parser has to extract the shebang separately (at least syn does) so it could provide a hint - but not relying on it makes more sense.