netstandard2.1 compiling error: CS8987 The ‘scoped’ modifier of parameter ‘value’ doesn’t match overridden or implemented member about memorypack HOT 5 CLOSED

Thank you for reporting.
can't compile when targetframework is netstandard2.1 and C#11 environment, it is a bug.
I've fixed and released at 1.7.7, please try it.

from memorypack.

Tested positive! thanks for light speed, lol
but seems still require dual-targeting of certain arrangement to ensure successful compile.

Otherwise, you'll seemingly get:
[Case1] runtime error: "System.TypeLoadException: Message=Virtual static method 'RegisterFormatter' is not implemented on type 'xxx' from assembly ...", when net7.0 using 2.1-only lib which uses 2.1-only lib.
Or,
[Case2] compile error: "CS8920: The interface ‘{0}’ cannot be used as type argument. Static member ‘{1}’ does not have a most specific implementation in the interface.", if net7.0 using dual-targeting lib which uses 2.1-only lib, when a MemoryPackable interface involved (this might be another issue).

[Case3] net7.0 using net 7.0-only lib which uses 2.1-only lib also yields CS8920, if MemoryPackable Interface is involved.
When replace the interface with a class which implementing it, it compiles but yield runtime error: "System.TypeLoadException" as described above.

[Case4] The only working combination is : net7.0 using dual-targeting lib which uses dual-targeting lib. (in case MemoryPackable Interface involved, idk if it works otherwise when no interface involved)

Note: the interface was defined in the end-level 2.1-only lib, and was consumed in the intermediate lib.

My conclusion:
It seems net7.0 code cannot consume MemoryPackable net2.1lib anyway in any level, dual-targeting only benefit by making compile pass, so that these 2.1libs can be shared by other programs which r not compiled with net7.0, and MemoryPack won't work with them.
is it correct?

from memorypack.

Yes, I wrote about that just yesterday.
https://github.com/Cysharp/MemoryPack#target-framework-dependency

.NET 7 and .NET Standard 2.1 are not compatible.
Because static abstract members are a feature that requires a .NET 7 runtime update, and are the basis for performance in .NET 7 version of MemoryPack.
The 2.1lib is only to support net6 (and Unity) and is close to being a separate product.
This is a temporary measure as we believe this situation will not be a problem once net8 (LTS) is released.

from memorypack.

I saw that remarks but not quite understand its implication, for i had thought 2.1 libs may work with net7 consumers somehow and that'll be great for my legacy projects.
Now i know it, i.e. MemoryPack DOES NOT Support NET versions other than 7.0(so far), but Dual-targeting netstandard2.1 makes the compile Pass, -ONLY, and it doesn't mean u can consume MemoryPack in 2.1 libs. LOL

i think u may add a line like this for a better explanation. ;-)

from memorypack.

I agree, added more:)

from memorypack.