Generate fast-path serialize logic for nullable structs

[layomia]

The JSON source generator doesn't generate optimized serialization logic for nullable structs, but it could. The following method should be extended to include this support:

runtime/src/libraries/System.Text.Json/gen/JsonSourceGenerator.Emitter.cs

Line 353 in 7a58bef

private string GenerateForNullable(TypeGenerationSpec typeMetadata)

See also #51945.

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Issue Details

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The JSON source generator doesn't generate serialization logic for nullable structs, but it could. The following method should be extended to include this support:

runtime/src/libraries/System.Text.Json/gen/JsonSourceGenerator.Emitter.cs

Line 353 in 7a58bef

private string GenerateForNullable(TypeGenerationSpec typeMetadata)

See also #51945.

Author:	layomia
Assignees:	-
Labels:	area-System.Text.Json, up-for-grabs
Milestone:	7.0.0

[SkiFoD]

@layomia Hey, I would like to work on the issue. I have done some investigations and it seems I need your assistance.

[SkiFoD]

@layomia There are cases when a structs implements any enumerable interface. For example public struct MyListStruct : IList .... In these cases we can't use methods like CreateListInfo and etc because of the constraints they have, so the fast path can't be created. What do you think about that?

[layomia]

Closing as fast-past methods for underlying types are already being invoked - #60366 (comment).

[layomia]

@layomia There are cases when a structs implements any enumerable interface. For example public struct MyListStruct : IList .... In these cases we can't use methods like CreateListInfo and etc because of the constraints they have, so the fast path can't be created. What do you think about that?

If we really wanted to eek out the last mile of perf for nullable structs, we would need to add a new method to attach the generated fast-path logic to, e.g. CreateNullableOfTInfo or similar.