Hello,

I'm trying to create a mixin for quick binary operator overloads by passing in types with a corresponding associative array of strings to functions. However,
the code I currently have:

module foo;

mixin template opBi(
    A, A function(A, A)[string] f0,
) {
    static foreach (k, f; f0) { A opBinary(string op: k)(A r) { return f(this, r); } }
}

struct A {
    mixin opBi!(
        A, [ "+": (A a, A b) => a],
    );
}

struct B {
    mixin opBi!(
        B, [ "+": (B a, B b) => a],
    );
}

Will not let me override operators on both struct A and B.

I get:

foo.d(16): Error: mixin `foo.B.opBi!(B, ["+":function (B a, B b) pure nothrow @nogc @safe => a])` does not match template declaration `opBi(A, A function(A, A)[string] f0)`

Is this a bug or am I doing something wrong?

On 7/22/22 8:33 AM, Anthony Quizon wrote:

module foo;

mixin template opBi(
     A, A function(A, A)[string] f0,
) {
     static foreach (k, f; f0) { A opBinary(string op: k)(A r) { return f(this, r); } }
}

struct A {
     mixin opBi!(
         A, [ "+": (A a, A b) => a],
     );
}

struct B {
     mixin opBi!(
         B, [ "+": (B a, B b) => a],
     );
}

foo.d(16): Error: mixin `foo.B.opBi!(B, ["+":function (B a, B b) pure nothrow @nogc @safe => a])` does not match template declaration `opBi(A, A function(A, A)[string] f0)`

It's typing the AA differently, and therefore it doesn't fit. The type of the AA you are passing in is T1[string], where it's expecting T2[string], where:

T1 is B function(B, B) pure nothrow @nogc @safe
T2 is B function(B, B)

I don't know if there's a better way to do this, other than use a further template parameter to match the function type passed in.

-Steve

On Friday, 22 July 2022 at 12:33:37 UTC, Anthony Quizon wrote:

foo.d(16): Error: mixin `foo.B.opBi!(B, ["+":function (B a, B b) pure nothrow @nogc @safe => a])` does not match template declaration `opBi(A, A function(A, A)[string] f0)`

Looks like this bug:

https://issues.dlang.org/show_bug.cgi?id=22540