Re: Different visibility in template for class and struct?
On Monday, 11 May 2020 at 16:10:36 UTC, Steven Schveighoffer
wrote:
On 5/11/20 11:40 AM, Shigeki Karita wrote:
On Monday, 11 May 2020 at 15:29:53 UTC, Steven Schveighoffer
wrote:
[...]
Thanks for your answer. Now I understand that POD matters here.
When I add a dtor: `struct LocalS { ~this() {} }`, the
`p!LocalS` got false.
There is still a bug though. if p!T returns true, but make!T
doesn't compile, then something is inconsistent.
-Steve
I agree. This should be a bug
https://wandbox.org/permlink/5YoKKt8xjdexzJHp
Re: Different visibility in template for class and struct?
On 5/11/20 11:40 AM, Shigeki Karita wrote:
On Monday, 11 May 2020 at 15:29:53 UTC, Steven Schveighoffer wrote:
On 5/11/20 11:11 AM, Shigeki Karita wrote:
[...]
First, it actually does compile, I think because the compiler
recognizes that LocalS is POD (plain old data), without methods, so it
doesn't need a context pointer.
e.g.:
auto make(T)() { return new T(); }
...
auto x = make!LocalS; // ok
If you add a method to LocalS, then make!LocalS fails to compile.
However, strangely, p!LocalS still returns true, I think that is an
error.
Thanks for your answer. Now I understand that POD matters here.
When I add a dtor: `struct LocalS { ~this() {} }`, the `p!LocalS` got
false.
There is still a bug though. if p!T returns true, but make!T doesn't
compile, then something is inconsistent.
-Steve
Re: Different visibility in template for class and struct?
On Monday, 11 May 2020 at 15:29:53 UTC, Steven Schveighoffer
wrote:
On 5/11/20 11:11 AM, Shigeki Karita wrote:
[...]
First, it actually does compile, I think because the compiler
recognizes that LocalS is POD (plain old data), without
methods, so it doesn't need a context pointer.
e.g.:
auto make(T)() { return new T(); }
...
auto x = make!LocalS; // ok
If you add a method to LocalS, then make!LocalS fails to
compile. However, strangely, p!LocalS still returns true, I
think that is an error.
-Steve
Thanks for your answer. Now I understand that POD matters here.
When I add a dtor: `struct LocalS { ~this() {} }`, the `p!LocalS`
got false.
Re: Different visibility in template for class and struct?
On 5/11/20 11:11 AM, Shigeki Karita wrote:
Why is local struct visible in this outer template, while local class is
not?
https://wandbox.org/permlink/MfsDa68qgaMSIr4a
https://dlang.org/spec/template.html#instantiation_scope
---
enum p(T) = __traits(compiles, new T());
class GlobalC {}
struct GlobalS {}
void main()
{
class LocalC {}
static assert(p!GlobalC);
static assert(!p!LocalC);
struct LocalS {}
static assert(p!GlobalS);
static assert(p!LocalS); // ??
}
First, it actually does compile, I think because the compiler recognizes
that LocalS is POD (plain old data), without methods, so it doesn't need
a context pointer.
e.g.:
auto make(T)() { return new T(); }
...
auto x = make!LocalS; // ok
If you add a method to LocalS, then make!LocalS fails to compile.
However, strangely, p!LocalS still returns true, I think that is an error.
-Steve
Different visibility in template for class and struct?
Why is local struct visible in this outer template, while local
class is not?
https://wandbox.org/permlink/MfsDa68qgaMSIr4a
https://dlang.org/spec/template.html#instantiation_scope
---
enum p(T) = __traits(compiles, new T());
class GlobalC {}
struct GlobalS {}
void main()
{
class LocalC {}
static assert(p!GlobalC);
static assert(!p!LocalC);
struct LocalS {}
static assert(p!GlobalS);
static assert(p!LocalS); // ??
}
