Module level mixin templates conflict

[dlangBugzillaToGithub]

timon.gehr reported this on 2014-04-26T21:44:34Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=12659

CC List

• Marco Leise
• Vlad Levenfeld

Description

With DMD 2.065, the following code fails to compile:

import std.stdio;

mixin template Foo(T){
    T foo(T a){ return a; }
}
mixin Foo!int g;
mixin Foo!string g;

void main(){
    writeln(foo(2));
    writeln(foo("a"));
    writeln(g.foo(2));
    writeln(g.foo("a"));
}

Error: mixin tt.Foo!(string) conflicts with mixin tt.Foo!(int) at tt.d(6)

Similarly if two named mixins occur in different files:

module b;
mixin template Foo(T){
    T foo(T a){ return a; }
}
mixin Foo!string g;

// ---

module c;
mixin template Foo(T){
    T foo(T a){ return a; }
}
mixin Foo!int g;

// ---

import std.stdio;
import b,c;

void main(){
    writeln(foo(2));
    writeln(foo("a"));
    writeln(g.foo(2));
    writeln(g.foo("a"));
}

Error: b.Foo!(string) at b.d(5) conflicts with c.Foo!(int) at c.d(5)
Error: function b.Foo!(string).foo (string a) is not callable using argument types (int)
Error: cannot implicitly convert expression (2) of type int to string
Error: b.Foo!(string) at b.d(5) conflicts with c.Foo!(int) at c.d(5)

Both examples should compile.

[dlangBugzillaToGithub]

Marco.Leise commented on 2016-09-17T13:57:34Z

Generally, symbols mixed in at module level conflict. E.g.:

  mixin template Preparer()
  {
  	bool isPrepared;
  }

when mixed into multiple modules causes conflicts when accessing `isPrepared`. In particular `fully.qualified.module.name.isPrepared` does not help the compiler distinguish the symbols either.