internal: seal singleton-style types with no accessible constructor - #424
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PhoneNumberUtil, PhoneNumberOfflineGeocoder, PhoneNumberToCarrierMapper, PhoneNumberToTimeZonesMapper, and ShortNumberInfo all have internal or private constructors and are reached only through GetInstance() - no external assembly could ever have subclassed them, and nothing in this repo does either. MetadataFilter is also sealed: its own doc comment already says it's "an internal API ... not part of the public API", every member but the class declaration and the object overrides is already internal. Verified locally with `dotnet pack -p:VersionPrefix=9.0.38` against the 9.0.37 ApiCompat baseline that sealing these produces zero CP-rule errors - the CP0009 "sealed added" rule only fires for a type with an accessible (public/protected) constructor. (Tried making MetadataFilter `internal` too, matching its doc comment, but that trips CP0001 "type removed" regardless of constructor accessibility, so it stays public and just gains `sealed` - see the correction posted on #375.) Follow-up from the #375 audit. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #424 +/- ##
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- Coverage 87.46% 87.40% -0.06%
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Files 41 41
Lines 3837 3835 -2
Branches 984 985 +1
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- Hits 3356 3352 -4
- Misses 280 281 +1
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This was referenced Aug 28, 2026
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Summary
Part of the sealing/visibility audit from #375 (comment: #375 (comment)) — this PR is the "safe now, not blocked on a major version" bucket.
PhoneNumberUtil,PhoneNumberOfflineGeocoder,PhoneNumberToCarrierMapper,PhoneNumberToTimeZonesMapper,ShortNumberInfo→sealed. All are reached only through a staticGetInstance(); their constructors areinternal/private, so no external assembly could ever have derived from them, and nothing in this repo does either.MetadataFilter→sealed. Its own doc comment already says it's "an internal API ... not part of the public API"; every member except the class declaration and theobjectoverrides is alreadyinternal.Verified locally that this is genuinely non-breaking: ran
dotnet pack -p:VersionPrefix=9.0.38against the9.0.37EnablePackageValidationbaseline.sealedon a type with no accessible constructor produces zero ApiCompat errors — theCP0009"sealed added" rule only fires when the baseline type had a public/protected constructor. (I also tried makingMetadataFilterinternaloutright, matching its doc comment, but that tripsCP0001"type removed from the public API surface" regardless of constructor accessibility — so it stayspublic, just sealed. Posted that correction on #375 too.)No behavior change.
Test plan
dotnet build csharp/PhoneNumbers.slnx— clean, 0 warningsdotnet test csharp/PhoneNumbers.slnx -p:TargetFrameworks=net10.0— 450/450 passing (414 PhoneNumbers.Test + 36 PhoneNumbers.Extensions.Test)dotnet pack -c Release csharp/PhoneNumbers -p:VersionPrefix=9.0.38— ApiCompat clean against the 9.0.37 baseline