Unverified50% confidenceFactExact time
The compiler obtains the complete set of direct subtypes from the sealed class's permits list and recursively analyzes them in conjunction with the subtypes' sealedness; non-sealed subclasses of a sealed interface are treated as open types and require a default branch.
1
Sources
50%
Confidence
Long-term
Relevance
10/18/2026
First Seen
Sources
Related Entities
Related Claims
UnverifiedThe TypeFamilies extension allows the definition of type-level functions, which fall into closed and open varieties; open type families can have instances defined incrementally across multiple modules.73% similarUnverifiedSealed classes explicitly declare the permitted subtypes via the permits clause, turning inheritance relationships from open to controlled.72% similarUnverifiedTypeScript's type narrowing allows the compiler to obtain more precise type information in specific code branches through conditional checks.70% similarUnverifiedDependent types allow types themselves to depend on values—for example, one can define a type of 'list of length n'—enabling many runtime properties to be statically guaranteed at compile time.70% similar
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