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digitalmars.D.bugs - [Issue 12532] New: __traits(compiles, ...) fails to see valid enum symbols

reply d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=12532

           Summary: __traits(compiles, ...)  fails to see valid enum
                    symbols
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: 2krnk gmx.net



under certain circumstances, eg when called from a template using mixin and
static if, __traits(compiles, ...)  fails to see valid enum symbols. (if 'enum'
in following example is replaced by 'const bool' or 'immutable bool' all
symbols are found.)

=== EXAMPLE ===

template valid(string mem){
    pragma(msg, "instantiation of 'valid' with: "~mem);
    static if( !__traits( compiles, mixin(mem) ) ){
        enum valid = false;
    }else{
        enum valid =  true;
     }
}

enum ok = valid!"works";
pragma(msg, "found 'works'? "~ok.stringof );
// true - fine, recognizes 'works' later in module scope

enum foo = valid!"bar";
pragma(msg, "found 'bar'? "~foo.stringof );
// true - fine, recognizes 'bar' laterin module scope

enum bar = valid!"foo";
pragma(msg, "found 'foo'? "~bar.stringof );
// false - fails to see 'foo' earlier in module scope!

enum works = true;

void main(){}

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next sibling parent d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=12532


monarchdodra gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |monarchdodra gmail.com



Reduced:

//----
enum a = is(typeof(b));
enum b = is(typeof(a));

pragma(msg, a); //true
pragma(msg, b); //false
//----

I'm not sure this is actually resolvable...?

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prev sibling parent d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=12532






 Reduced:
 
 //----
 enum a = is(typeof(b));
 enum b = is(typeof(a));
 
 pragma(msg, a); //true
 pragma(msg, b); //false
 //----
 
 I'm not sure this is actually resolvable...?


sorry, i should have reduced it to

enum a = __traits(compiles, b);
pragma(msg, a);                 // true
enum b = __traits(compiles, a);
pragma(msg, b);                 // false

guess i was too preoccupied with issue 12533. however, i think b should be
true, __traits(compiles, ...) should not need the value or type of a. in other
words, it should be able to see that a symbol is defined without caring what it
actually is. as a matter of fact, in

enum c;
pragma(msg, typeof(c));         // _error_
pragma(msg, is(typeof(c)) );    // false
enum d = __traits(compiles, c);
pragma(msg, d);                 // true

this is kinda happening.

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