Provide tests for Rust 1.4

[matklad]

There is at least one language change that is currently not covered by tests: rust-lang/rust#27451

FYI: we are using ctrs in tests in https://github.com/alexeykudinkin/intellij-rust and it helps us a lot :)

[brson]

Wow! I'm glad you are using it. Maybe this will inspire me to whip it into shape.

[matklad]

Let me provide you with our experience with ctrs then :)

We use it to "verify" our parser. That is, we check that every file parses somehow.

We do not verify that the parse tree is right, because we don't have a correct answer to compare with. In general I don't think it is feasible to compare concrete parse trees, because they will be different in details.

It might be possible to compare lexical structure though. @winger even wrote a comparison tool: winger/intellij-rust@62e5d81. We don't use it now because of the difficulties of maintaining rust subproject within Java/Kotlin codebase.

[brson]

@matklad I'm in the process of rewriting the python test driver as a cargo project (it will use build scripts to generate rust #[test] cases that call to rustc to run the tests). I know you aren't using the provided test driver now, but will this be more or less convenient for you?

[matklad]

I don't know :) It should not matter much, because from Java point of view it will be just different external processes.

Rust might be sightly easier to distribute: if you are messing with ctrs then most likely you have cargo installed, but, if you are using Windows, Python may be absent.

[brson]

Updated for 1.4.

[matklad]

FYI: we've drop ctrs from IntelliJ Rust test suite and test our parser on the compiler and standard library sources instead.

The main reason is that we must support nightly features, because the standard library uses them.

[brson]

@matklad Thanks for the update. Sorry I haven't maintained this thing.