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digitalmars.D - super simple code, super slow to compile

reply Basile B. <b2.temp gmx.com> writes:
I've found this yesterday while exploring issues:

---
import std.typecons: Typedef;
alias Matrix = double[260][260];
alias Foo = Typedef!Matrix;
void main() {}
---

It's super slow to compile, here 2 seconds. Change the dimension 
of the 2nd static array type to 10 and it's more acceptable.

At first glance I'd say that the compiler is doing something 
stupid.
Mar 30 2019
parent reply Basile B. <b2.temp gmx.com> writes:
On Sunday, 31 March 2019 at 05:37:25 UTC, Basile B. wrote:

 I've found this yesterday while exploring issues:

 ---
 import std.typecons: Typedef;
 alias Matrix = double[260][260];
 alias Foo = Typedef!Matrix;
 void main() {}
 ---

 It's super slow to compile, here 2 seconds. Change the 
 dimension of the 2nd static array type to 10 and it's more 
 acceptable.

 At first glance I'd say that the compiler is doing something 
 stupid.


Well it's not dmd that does something stupid, it's phobos.
Typedef default initializer is stored in the type signature.
  init as template param should be void and in this case void 
would be used to set the payload to the actual init. When people 
want real void init they can do them the classic way anyway

alias M = Typedef!Matrix; // Typedef!(Matrix, void, null);
M m = void;

gotta make a PR lol.
Mar 31 2019
parent Basile B. <b2.temp gmx.com> writes:
On Sunday, 31 March 2019 at 07:31:57 UTC, Basile B. wrote:

 On Sunday, 31 March 2019 at 05:37:25 UTC, Basile B. wrote:

 [...]


 Well it's not dmd that does something stupid, it's phobos.
 Typedef default initializer is stored in the type signature.
  init as template param should be void and in this case void 
 would be used to set the payload to the actual init. When 
 people want real void init they can do them the classic way 
 anyway

 alias M = Typedef!Matrix; // Typedef!(Matrix, void, null);
 M m = void;

 gotta make a PR lol.


Mmmh CTFE doesn't accept uninitialized variables...
To solve the issue the template parameter must be dropped 
entirely.
Mar 31 2019