Test plan for "closed class hierarchies" feature #81039
Description
Championed proposal: dotnet/csharplang#9499
Speclet: https://github.com/dotnet/csharplang/blob/main/proposals/closed-hierarchies.md
Compiler:
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Championed proposal: dotnet/csharplang#9499
Speclet: https://github.com/dotnet/csharplang/blob/main/proposals/closed-hierarchies.md
Compiler: