On Sunday, 13 November 2022 at 19:06:40 UTC, 0xEAB wrote:
Why does only the latter sample compile?
The former leads to the following warning:
Are you using the `-preview=dip1000` compiler flag?
I didn't manage to reproduce this in a simple example of my own.
The closest I equivalent I accomplished is this:
```
enum LowerCaseToken { u, l, c }
struct Foo {
@safe:
int* dummy;
string[int][LowerCaseToken] _headers;
this(return ref int i)
{
dummy = &i;
}
string[] getHeader(LowerCaseToken name) scope return
{
return _headers[name].values;
}
string[] getHeader(string name)() scope return
{
enum token = LowerCaseToken.l;
// Error. Remove to compile
auto x = &this;
return this.getHeader(token);
}
}
@safe void main()
{
int x;
auto foo = Foo(x);
foo.getHeader!"h1"();
}
```
With `-preview=dip1000` this fails, but with a slightly different
message to yours, "cannot take address of `scope` parameter
`this` in `@safe` function `getHeader`". It's right to fail,
because you cannot have any pointer (or array, or class) to point
to a `scope` variable. D does not have any storage class for `x`
that would protect the int pointed to by `dummy`, because
`scope(Foo*)` means address of Foo is protected, not the address
of whatever `dummy` and `_headers` point to.
However, this error only happens if I try to create a pointer to
`this`, not when simply using `this`, plus the error is a bit
different, so I'm not sure what's going on.
(and why is the deprecation message printed twice?)
The function is a template. Perhaps it's instantiated twice.
Another possibility, you have instantiated the mixin template
that contains that function in your project twice.
