Top level checks are only used for miniscript APIs and not descriptor APIs.

[sanket1729]

    #[test]
    fn test_2() {
        let desc = Descriptor::<String>::from_str("wsh(thresh(1,pk(A),s:pk(B)))").unwrap();
        let desc = Descriptor::<String>::from_str("wsh(thresh(1,pk(A),s:pk(A)))").unwrap(); // This should also ERR because duplicate keys.
        
        // But miniscript APIs are fine.
        let ms = Miniscript::<String, Segwitv0>::from_str("thresh(1,pk(A),s:pk(B))").unwrap();
        let ms = Miniscript::<String, Segwitv0>::from_str("thresh(1,pk(A),s:pk(A))").expect_err("This is not a valid miniscript");
    }

bitcoinfuzz/bitcoinfuzz#73 (comment)

We should have those in descriptor APIs too. In the above example, we have duplicate keys being allowed in descriptors.

[apoelstra]

I plan to address this in 2025 by overhauling our sanity check system.

[erickcestari]

@apoelstra how's it going?

[apoelstra]

@erickcestari I have a private 56-commit branch in which I have successfully implemented a new ValidationParams type which contains the size limits, the sanity rules, the key-related rules, etc. And I use this as the exclusive set of checks on the Miniscript type. Along the way I also introduced strong error types for string parsing and script decoding. I would like to add position/span information to these errors but that's not done yet.

I would like also to use it on the two Policy types but I haven't done that yet. I would also like to get rid of the Ctx parameter on the Miniscript type but even after 50+ commits of refactoring there's still more hacking to do.

Anyway once @sanket1729 merges #815 I'll start PRing the stuff that I've got in bits and pieces.

[erickcestari]

@erickcestari I have a private 56-commit branch in which I have successfully implemented a new ValidationParams type which contains the size limits, the sanity rules, the key-related rules, etc. And I use this as the exclusive set of checks on the Miniscript type. Along the way I also introduced strong error types for string parsing and script decoding. I would like to add position/span information to these errors but that's not done yet.

I would like also to use it on the two Policy types but I haven't done that yet. I would also like to get rid of the Ctx parameter on the Miniscript type but even after 50+ commits of refactoring there's still more hacking to do.

Anyway once @sanket1729 merges #815 I'll start PRing the stuff that I've got in bits and pieces.

Cool, thanks for the overview! Looking forward to seeing your PRs.