• d-bugmail puremagic.com Jan 14 2013

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=9319

           Summary: Unexpected compiles __traits behaviour in a certain
                    situation
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: puneet coverify.org


--- Comment #0 from Puneet Goel <puneet coverify.org> 2013-01-14 11:12:38 PST
---
"static if" on the line number 3 should take the else branch, but it does not
and compilation actually fails on line number 6, giving me error:

Error: this for foo needs to be type Derived not type Base

BTW, it is failing for nested (inside base class) template, but seems to work
fine for function template (line 16).

class Base {                                                      // 1
  template Bar(alias F) {                                         // 2
    static if(__traits(compiles, F())) {                          // 3
      pragma(msg, F.stringof ~ " compiles here"); // prints this  // 4
      class Bar {                                                 // 5
        this() { F(); }         // but actual compilation fails   // 6
      }                                                           // 7
    } else {                                                      // 8
      pragma(msg, F.stringof ~ " does not compile");              // 9
      class Bar {                                                 // 10
        this() { }                                                // 11 
      }                                                           // 12 
    }                                                             // 13 
  }                                                               // 14 
                                                                  // 15 
  public void bar(alias F)() {                                    // 16 
    static if(__traits(compiles, F())) { // works as expected     // 17 
      F();                                                        // 18 
    }                                                             // 19 
  }                                                               // 20
}                                                                 // 21 
                                                                  // 22 
class Derived: Base {                                             // 23 
  public void foo() {}                                            // 24 
  public Bar!foo boo;                                             // 25 
  public void frop() {                                            // 26 
    bar!foo;                                                      // 27 
    boo = new Bar!foo;                                            // 28 
  }                                                               // 29 
}                                                                 // 30
                                                                  // 31 
void main() {                                                     // 32 
  auto obj = new Derived;                                         // 33 
  obj.frop();                                                     // 34 
}                                                                 // 35

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