Implicit conversion to mutable if no indirections?

[Ali Çehreli]

An issue I have is non-mutable expressions without indirections not 
converting to mutable. I talked about this before and mentioned Unqual 
at DConf 2022 to explain how it solves this.

The problem happens in template code:

void main() {
   const i = 42;  // const, so foo's T will be const below
   foo(i);
}

void foo(T)(T value) {
   T result;
   ++result;  // Compilation error; but should it work?
}

I feel like it should work because 'result' is a local int.

But I am aware that we can't deduce T to be 'int' because we would be 
losing that qualifier and further template deductions would be wrong. :/

Anyway... That's one thing that bugs me occasionally and causes bugs 
like the following one, which I think is caused by a missing Unqual:

   https://issues.dlang.org/show_bug.cgi?id=23319

At least, there is a moral here at least for myself: Don't forget to 
test your templates with const, etc.

Ali