Wrong behavior when using records with primary constructors and inheritance?

[Fabi]

In the latest .NET 5 preview I played around with records and noticed a for me unexpected behavior.

Given 2 records

record R1(int P1);
record R2 : R1(1);

This will result in

and

My expectation would have been that the old behavior of the first version of primary constructors would still work here.
Old behavior = It would call the constructor of R1 with the value 1 and creates R2 with the default ctor call.

Currently it seems that R2 that R1 got an empty constructor defined and R1 expects R2 to have an argument list that matches the given one.

record R1(int P1);
record R2(int P1) : R1(1);

would work but this actually doesn't make any sense for me.
And using an empty parameter list on R2 doesn't seem to be supported (why???)

[Youssef1313]

Related to (or duplicate of) #47816
Currently, you'd need to use record R2() : R1(1) instead of record R2 : R1(1)

[tomrus88]

When you use record R2() : R1(1), it will give you Error CS8850 A positional record must have a non-empty parameter list

[Fabi]

When you use record R2() : R1(1), it will give you Error CS8850 A positional record must have a non-empty parameter list

Yea thats what I ment with Currently it seems that R2 that R1 got an empty constructor defined and R1 expects R2 to have an argument list that matches the given one.

() would be old behavior too tho

[Youssef1313]

Error CS8850 was removed from the compiler. I'm not sure of the exact version it was removed in.

[tomrus88]

CS8850 is in latest VS Preview 16.8.0 Preview 3.2, so if it was removed, it happened very recently.

[Fabi]

Just tested it. works through .NET 5 RC2 command line building but not in Visual Studio Preview.

[Youssef1313]

CS8850 is in latest VS Preview 16.8.0 Preview 3.2, so if it was removed, it happened very recently.

Yeah I just checked. It was just 2 weeks ago in #47805

But I still agree it should work without adding empty parentheses (or at least, a better error message that suggests adding the empty parentheses).

[PathogenDavid]

@Fabi

If you need this change sooner rather than later, the easiest way to do so is to add a reference to the Microsfot.Net.Compilers.Toolset package. (You'll need to have the pre-release NuGet feed configured as well.)

(Note that the IDE might still show errors when using this package, but it'll build.)

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But I still agree it should work without adding empty parentheses (or at least, a better error message that suggests adding the empty parentheses).

Currently the spec requires the empty parameter list, but LDM has expressed interest in making it optional. It might not make it for C#9 though.