Top level or-patterns are not allowed let binding

[MahadMuhammad]

Top level or-patterns are not allowed let binding - E0658

• This error code is emitted by rustc 1.49.0, but not emitted by rustc -nightly.
• I have updated according to rustc 1.49.0, as we are targeting rustc 1.49.0 testsuite.
• See the difference here godbolt

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gcc/rust/ChangeLog:

* hir/rust-ast-lower-pattern.cc (ASTLoweringPattern::visit): Added richlocation & error code.

gcc/testsuite/ChangeLog:

* rust/compile/let_alt.rs: Updated comment.

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[MahadMuhammad]

This message and errorcode is according to rustc 1.49.0, rustc nighly not emit E0658 (An unstable feature was used) as this was unstable feature in rustc 1.49.0.

Should we add the latest verion message, or stick to rustc 1.49.0

[CohenArthur]

We can't use E0658 here, as E0658 refers to the use of unstable features. In 1.49, top level or patterns were considered an unstable feature, which is why the compiler emitted E0658. It's now been stabilized. So the handling here needs to be a little different.

The error in itself does not have an error code. So we cannot have one either.

We then have to decide if we want to implement top level or-patterns (if they are needed by core or std, we'll need to implement them, but otherwise no) and go from there.

Furthermore, in Rust 1.49 with nightly features let a | a = 15 is valid, but not in Rust 1.53 when toplevel or-patterns were stabilized. You need to use let (a | a) = 15.

[CohenArthur]

I think improving the error message is nice, and we should remove the error code from the error message. Looks good to me apart from this :)

[CohenArthur]

We can't use E0658 here, as E0658 refers to the use of unstable features. In 1.49, top level or patterns were considered an unstable feature, which is why the compiler emitted E0658. It's now been stabilized. So the handling here needs to be a little different.

The error in itself does not have an error code. So we cannot have one either.

We then have to decide if we want to implement top level or-patterns (if they are needed by core or std, we'll need to implement them, but otherwise no) and go from there.

Furthermore, in Rust 1.49 with nightly features let a | a = 15 is valid, but not in Rust 1.53 when toplevel or-patterns were stabilized. You need to use let (a | a) = 15.

[CohenArthur]

Looks great!