Type for default literal not inferred in C# 7.0

[Neme12]

It seems the type for a default literal is not correctly inferred when using C# 7.0 or lower. In these cases:

class C
{
    int M()
    {
        return default;
    }
}

class C
{
    void M(int a)
    {
        M(default);
    }
}

class C
{
    void M()
    {
        var i = true ? 0 : default;
    }
}

class C
{
    void M()
    {
        var i = (int)default;
    }
}

calling GetTypeInfo().ConvertedType on the default literal results in an error type. This works as expected (returns int type) when using C# 7.1. Some simple cases work in C# 7.0 too such as int i = default; and switch (0) { case default: }; (both return int for converted type on the default literal).

Is this by design? I think it would be good for the compiler to infer the type even when the language version isn't right, for good error recovery in the IDE. If that's not possible or desired, would it at least be possible to somehow find out what the type would have been if there wasn't an error? Thanks.

(Discovered in #30359 (comment))

Tagging @jcouv

[Neme12]

There is a similar issue here. GetConstantValue isn't working either for default literals in C# 7.0, even in simple cases. For example:

class C
{
    void M()
    {
        int i = default;
    }
}

Calling GetConstantValue on the default literal returns no value. This is blocking work on another feature (converting default to another literal). Please let me know if this is unrelated and I should file a separate issue. Thanks.