Duplicate `.override method` generation

[viceroypenguin]

Duplicate `.override method` generation

[viceroypenguin]

build.zip

[jjonescz]

Looks like this is caused by different nullability contexts (generated files have different nullability context that's why you couldn't repro without source generators probably). Can reproduce with something as simple as:

#nullable enable
partial class C
    #nullable disable
    : IInterface<C>
    #nullable enable
{
}

partial class C : IInterface<C>
{
    public static void M() { }
}

interface IInterface<T>
{
    static abstract void M();
}

See SharpLab.

Results in this IL (notice the duplicate .override method):

.class private auto ansi beforefieldinit C
    extends [System.Runtime]System.Object
    implements class IInterface`1<class C>
{
    // Methods
    .method public hidebysig static 
        void M () cil managed 
    {
        .override method void class IInterface`1<class C>::M()
        .override method void class IInterface`1<class C>::M()
        // Method begins at RVA 0x2050
        // Code size 1 (0x1)
        .maxstack 8

        IL_0000: ret
    } // end of method C::M

Similar issue I've stumbled upon recently in razor: #40538 (via dotnet/razor#9837).