what are the rules for @nogc and @safe attributes inference?

[Alex]

On Friday, 16 November 2018 at 10:25:26 UTC, ikod wrote:
> On Thursday, 15 November 2018 at 21:55:18 UTC, Steven 
> Schveighoffer wrote:
>> On 11/15/18 4:09 PM, Adam D. Ruppe wrote:
>>> On Thursday, 15 November 2018 at 21:00:48 UTC, ikod wrote:
>>>> what are the rules for @nogc inference?
>>> 
>>> It attempts it if and only if it is a template.
>>
>> Well, the general "rule" is, if it's code that must be 
>> available to the compiler when it's called, then it will be 
>> inferred.
>>
>> Examples of code that must be processed every time it's used:
>>
>> 1. Template functions
>> 2. auto-returning functions
>> 3. functions inside templates (like member functions of a 
>> templated struct)
>> 4. Inner functions
>>
>> There may be others I didn't think of.
>>
>> Everything else must be manually attributed. The reasoning is 
>> that the function may be stubbed in a .di file, and in that 
>> case, attribute inference wouldn't be possible.
>>
>> -Steve
>
> Thanks for clarifications, Adam and Steven!
>
> My problem is next code:
> =================================================
> import std.traits;
>
> T library_func(T)(/*lazy*/ T i)
> {
>     // this fuction can be @nogc or not depending on T 
> properties
>     static if (isArray!T) {
>         return i ~ i;
>     }
>     else
>     {
>     	return i;
>     }
> }
> void user_function_nogc() @nogc
> {
>     int x = 1;
>     library_func(x+1);
> }
> void user_function_gc()
> {
>     library_func([1]);
> }
> void main()
> {
> }
> =====================================================
> This code compiles as long as `lazy` is commented out. But I'd 
> like to have
> both lazy parameter and @nogc inferrence for `library_func` so 
> that user is not locked to code @nogc or not.

Aha, aha... Interesting!
I had a similar problem with passing a delegate. And it was 
solved:
https://forum.dlang.org/thread/erznqknpyxzxqivawnix@forum.dlang.org

For your problem, there is a bug report:
https://forum.dlang.org/post/wedwfooqdxbwxttpmzim@forum.dlang.org
https://issues.dlang.org/show_bug.cgi?id=12664
https://issues.dlang.org/show_bug.cgi?id=12647