This code:
/// this is a ddoc comment
void foo(int i) { printf("%d\n", i); }
/// ditto
void foo(uint i) { printf("%d\n", i); }
/// ditto
void foo(short i) { printf("%d\n", i); }

Generates this correct HTML documentation:

void foo(int i);
void foo(uint i);
void foo(short i);
    this is a ddoc comment 


Then I have tried to generate those similar functions with a mixin(), but then I can't find a way to make ddoc list them (into the generated Html) grouped:

/// this is a ddoc comment
void foo(int i) { printf("int) %d\n", i); }

template Gen(string type) {
    const Gen = `
    /// ditto
    void foo(` ~ type ~ ` i) { printf("` ~ type ~ `) %d\n", i); }`;
}

/// ditto
mixin(Gen!("uint"));

/// ditto
mixin(Gen!("short"));

void main() {
    foo(10);
    foo(cast(uint)20);
    foo(cast(short)30);
}