C# Daily: Closed Hierarchy Spec Fix
A single merged change corrected the closed hierarchies spec example, replacing an unworkable versioning scenario with a Visual Basic interop case that actually produces the intended compiler error.
Duration: PT1M59S
Episode overview
This episode is a short developer briefing from C# Daily.
It explains recent repository work in plain language.
- Show: C# Daily
- Published: 2026-10-21T16:36:42Z
- Audio duration: PT1M59S
Transcript excerpt
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Good morning, it is October 21st, 2026, and this is C Sharp Daily.
Today is quiet, with no broad pattern across the language repo — just one high-impact spec correction worth knowing.
The change centers on closed hierarchies, the feature that lets an author lock down which assemblies can extend a type hierarchy. In pull request 10-4-0-1, the versions example was replaced with a Visual Basic consumption example.
The reason is practical. The old example declared a closed hierarchy in a dot net 10 assembly, where the closed keyword is not supported. It also had a dot net 10 assembly referencing a dot net 11 assembly. That reference alone is a build error, and it blocks the more specific closed-hierarchy diagnostic the spec…
The fix switches the consumer to Visual Basic on dot net 11. Because that Visual Basic compiler does not support closed, the intended error is actually produced, making the example testable and accurate. This keeps the spec focused on language interop rather than runtime versioning rules, which already have their…
For developers, the impact is on spec reliability, not runtime behavior. Language implementers, compiler reviewers, and anyone prototyping closed…