Cannot use mutating member on immutable value: '$interpolation' is immutable

Using Swift
, ,
1

Hey! I'm currently trying to get something like this working:

@MyMacro("Hello \("world")")
struct MyType {}

The macro signature:

@attached(member)
macro Query(_ query: String)

The example above throws a mysterious error:

Cannot use mutating member on immutable value: '$interpolation' is immutable

Question: Does anyone have an idea what I'm doing wrong? I have never seen something like "$interpolation is immutable" before.

Many thanks in advance!

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