Is it possible to extend default interpolated-string handler to accept string.Join without an intermediate string allocation

[alrz]

Is there a way to avoid this kind of code to be emitted?

defaultInterpolatedStringHandler.AppendFormatted(string.Join(' ', a));

[stephentoub]

I'm not following. What C# code is generating that?

[alrz]

For example: $"abc{1}{string.Join(' ', a)}"

It's probably not possible to do this without changing the code, but I'm wondering if anything could be done here, maybe using a custom handler?

[stephentoub]

I'm wondering if anything could be done here, maybe using a custom handler

No, this would require roslyn to recognize string.Join and emulate its semantics by generating equivalent code.