cast to pure function stop work after upgrade

[vit]

On Monday, 14 June 2021 at 13:31:51 UTC, baby_tiger wrote:
> this used work for me, after upgrade I get this error.  how to 
> fix it ?
>
>
>     import std.traits;
>             enum LogLevel : ubyte {
>                     INFO = 0,
>                     WARN,
>                     ERROR,
>                     FATAL,
>             }
>
>
>     extern (C) string VFORMAT(LogLevel level, string file, 
> size_t line, char[] tmp, bool line_break, string tag, string 
> fmt, ...) @nogc nothrow {
>             return null;
>     }
>
>     template asPure(string P, alias Fn) if 
> (isFunctionPointer!(typeof(&Fn))) {
>             enum N = __traits(identifier, Fn);
>             enum string asPure = "private alias " ~ N ~ "_PURE 
> = " ~ typeof(&Fn).stringof ~ " pure;\n" ~ "__gshared immutable 
> " ~ N ~ "_PURE " ~ P ~"= cast(" ~ N ~ "_PURE) &" ~ N ~ " ;" ;
>     }
>     enum xx = asPure!("VFORMATP", VFORMAT);
>     mixin(xx);
>
> void main(){
>
> }
>
>
>      reinterpreting cast from `nothrow @nogc extern (C) 
> string(LogLevel level, string file, ulong line, char[] tmp, 
> bool line_break, string tag, string fmt, ...)*` to `pure 
> nothrow @nogc extern (C) string(LogLevel, string, ulong, 
> char[], bool, string, string, ...)*` is not supported in CTFE

```d
int foo(int x)@safe{
     return x;
}

/*
	This is valid.
	@safe CTFE cast, systemFoo has less restrictive function type.
   */
auto systemFoo = cast(int function(int)@system)&foo;

/*
	ERROR
	UNSAFE CTFE cast, pureFoo has more restrictive function type.
*/
//auto pureFoo = cast(void function(int)pure)&foo;

int function(int)pure pureFoo;

shared static this(){

	/*
         This is valid.
         UNSAFE RUNTIME cast.
	*/
	pureFoo = cast(int function(int)pure)&foo;
}


void main(){
	assert(pureFoo(42) == 42);
}
```