[Proposal]: Mixed object and collection initializers

[CyrusNajmabadi]

Mixed object and collection initializers

• Specification: https://github.com/dotnet/csharplang/blob/main/proposals/mixed-object-and-collection-initializers.md
• Discussion: [Proposal]: Mixed object and collection initializers #10186

Summary

Relax the existing restriction that a { ... } initializer following new T(...) must contain only member initializers or only element initializers. A single initializer would be allowed to contain any sequence of the two kinds, interleaved freely. Each element keeps its existing per-kind meaning — member_initializers assign to the named field/property/event (or invoke the indexer), and element_initializers invoke an Add method on the object being initialized.

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