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Unexpected "User-defined operator must be declared static and public" for an operator in an interface #52202

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AlekseyTs opened this issue Mar 28, 2021 · 1 comment · Fixed by #53119
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Unexpected "User-defined operator must be declared static and public" for an operator in an interface #52202

AlekseyTs opened this issue Mar 28, 2021 · 1 comment · Fixed by #53119
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@AlekseyTs
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Area-Compilers Bug New Language Feature - Default Interface Impl Default Interface Implementation
Milestone
16.10

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@AlekseyTs
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interface I2
{
    static I2 operator+ (I2 x)
    {throw null;}
}

Observed:

error CS0558: User-defined operator 'I2.operator +(I2)' must be declared static and public

Expected: No errors. members in interfaces are implicitly public.

There is also a question whether we should tie the fix to new language version or just fix it for C# 8.
@dotnet-issue-labeler dotnet-issue-labeler bot added the untriaged Issues and PRs which have not yet been triaged by a lead label Mar 28, 2021
@jaredpar jaredpar removed the untriaged Issues and PRs which have not yet been triaged by a lead label Mar 29, 2021
@jaredpar jaredpar added this to the 16.10 milestone Mar 29, 2021
@jaredpar
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I think we should just fix it for C# 8.0.

AlekseyTs added a commit to AlekseyTs/roslyn that referenced this issue Mar 29, 2021
@AlekseyTs
Allow abstract and sealed modifiers on static methods/properties/…
1cd7bb4 
…events in interafces.

Related to dotnet#52202.
@AlekseyTs AlekseyTs mentioned this issue Mar 29, 2021
Merged
AlekseyTs added a commit that referenced this issue Apr 2, 2021
@AlekseyTs
Allow abstract and sealed modifiers on static methods/properties/…
ff59bc0 
…events in interfaces. (#52228)

Spec: https://github.com/dotnet/csharplang/blob/9a0dddbf0643993db0da8f48436f2aac60bc20b1/proposals/statics-in-interfaces.md

Related to #52202.

Relevant quotes from the spec:

#### Abstract virtual members
Static interface members other than fields are allowed to also have the `abstract` modifier. Abstract static members are not allowed to have a body (or in the case of properties, the accessors are not allowed to have a body). 

``` c#
interface I<T> where T : I<T>
{
    static abstract void M();
    static abstract T P { get; set; }
    static abstract event Action E;
    static abstract T operator +(T l, T r);
}
```

#### Explicitly non-virtual static members
For symmetry with non-virtual instance members, static members should be allowed an optional `sealed` modifier, even though they are non-virtual by default:

``` c#
interface I0
{
    static sealed void M() => Console.WriteLine("Default behavior");
    
    static sealed int f = 0;
    
    static sealed int P1 { get; set; }
    static sealed int P2 { get => f; set => f = value; }
    
    static sealed event Action E1;
    static sealed event Action E2 { add => E1 += value; remove => E1 -= value; }
    
    static sealed I0 operator +(I0 l, I0 r) => l;
}
```
AlekseyTs added a commit to AlekseyTs/roslyn that referenced this issue May 3, 2021
@AlekseyTs
Operators declared in an interface must be implicitly public.
c69b10c 
Fixes dotnet#52202.
@AlekseyTs AlekseyTs mentioned this issue May 3, 2021
Merged
AlekseyTs added a commit that referenced this issue May 5, 2021
@AlekseyTs
Operators declared in an interface must be implicitly public. (#53119)
94ec99b 
Fixes #52202.
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@AlekseyTs AlekseyTs

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Area-Compilers Bug New Language Feature - Default Interface Impl Default Interface Implementation
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Operators declared in an interface must be implicitly public. AlekseyTs/roslyn
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@jaredpar @AlekseyTs