• Jack (9/9) Mar 01 2021 bool g(T)(T)
• Adam D. Ruppe (11/14) Mar 01 2021 So the value must be known at compile time without any extra
• H. S. Teoh (5/16) Mar 01 2021 https://wiki.dlang.org/User:Quickfur/Compile-time_vs._compile-time

Jack <jckj33 gmail.com> writes:

bool g(T)(T)
{
  	return __traits(compiles, mixin("{ enum a = t; }"));
}


int a;
enum s = "";
// both return false but g(s) is expected to return true
pragma(msg, g(s));
pragma(msg, g(a));

Adam D. Ruppe <destructionator gmail.com> writes:

On Monday, 1 March 2021 at 20:05:57 UTC, Jack wrote:
 int a;
 enum s = "";
 // both return false but g(s) is expected to return true

So the value must be known at compile time without any extra 
context. So that `a` variable might be changed somewhere else so 
compile time can't read or write it.

`enum` is only allowed to be set once (and at compile time!) so 
it is allowed at CT too.

`static immutable` generally allows it too since it must be set 
at declaration then never changed again.

But almost any mutable variable is no go unless it is directly 
returned from a function which itself can be called at compile 
time.

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Mon, Mar 01, 2021 at 08:05:57PM +0000, Jack via Digitalmars-d-learn wrote:
 bool g(T)(T)
 {
  	return __traits(compiles, mixin("{ enum a = t; }"));
 }
 
 
 int a;
 enum s = "";
 // both return false but g(s) is expected to return true
 pragma(msg, g(s));
 pragma(msg, g(a));

https://wiki.dlang.org/User:Quickfur/Compile-time_vs._compile-time


T

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