Support open generics in polymorphic serialization in System.Text.Json#127318

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Copilot wants to merge 8 commits intomainfrom

copilot/support-open-generics-serialization

Commits on Apr 23, 2026

Initial plan
Copilot
authored
Add open generic derived type support in polymorphic serialization

Copilot
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eiriktsarpalis
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Add comprehensive tests for open generic polymorphic serialization

Copilot
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eiriktsarpalis
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Update Polymorphism_TypeDoesNotSupportPolymorphism error message to say "open generic type definitions" instead of "generic types"

Copilot
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eiriktsarpalis
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Architectural rework: move MakeGenericType to reflection-only path, add source generator compile-time resolution

Copilot
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eiriktsarpalis
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Replace UnconditionalSuppressMessage with RequiresUnreferencedCode/RequiresDynamicCode propagation

Copilot
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jkotas
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Address review feedback: fix emitter pattern, sort derived types, refactor parser, remove doc comment, fix null guard, conditional PopulatePolymorphismMetadata

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jkotas
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Fix alphabetical ordering of type ref constants in Emitter

Copilot
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jkotas
authored