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digitalmars.D.bugs - [Issue 12533] New: instantiated template using __traits(compiles, ...) causes semantic errors when reused

reply d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=12533

           Summary: instantiated template using __traits(compiles, ...)
                    causes semantic errors when reused
           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


--- Comment #0 from det <2krnk gmx.net> 2014-04-06 16:39:50 PDT ---
compilation fails for no reason in given example involving a template using
mixin, static if and __traits(compiles, ...) code reflection. see details in
example as it is too complicated to describe.

might be related to issue 12532. however, example fails as well when 'enum' is
replaced by 'const'

=== 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 works = valid!"fails";
pragma(msg, "found 'fails' (via 'works')? "~works.stringof );
// compiles but produces 'false': issue 12532

enum dummy = valid!"fails";
pragma(msg, "found 'fails' (via 'dummy')? "~dummy.stringof );
// compiles but produces 'false': issue 12532

enum fails = valid!"fails";
// Error: variable demo.fails had semantic errors when compiling
// NOTE: if you comment out the first two usages of valid!"fails",
// it will work here - but give 'false' again.

//  pragma(msg, "found 'fails' (via 'fails')? "~fails.stringof );

void main(){}

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parent d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=12533



--- Comment #1 from det <2krnk gmx.net> 2014-04-07 22:50:35 PDT ---
(In reply to comment #0)

might be caused by issue 12541.

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