Compiler error when referencing a polymorphic type from within a polymorphic method which uses a trait whose methods operate on that same polymorphic type

[dkobets]

Example code:
an anonymous trait is created containing a method operating on a polymorphic type A, and a polymorphic method bar relying on this trait attempts to use A by instantiating it. A compiler error is generated

forall (otype T) {
    struct A {};
}

forall (otype T | {void foo(A(T));}) {
    void bar() {
        A(T) T;
    }
}

int main() {}

---

main.cfa: In function '_X3barQ1_0_0_5X16_operator_assignFBD0_BD0BD0X12_constructorFv_BD0X12_constructorFv_BD0BD0X11_destructorFv_BD0X3fooFv_S1A_BD0_Fv_1':
main.cfa:10:46: error: '_sizeof_S1A_Y1T_' undeclared (first use in this function)

void bar() {

main.cfa:10:46: note: each undeclared identifier is reported only once for each function it appears in

---

The same compiler error is generated when the trait is not anonymous

---

Removing the requirement on A in the trait resolves the issue:

forall (otype T) {
    struct A {};
}

forall (otype T | {void foo(T);}) {
    void bar() {
        A(T) T;
    }
}

int main() {}

using the -CFA flag during compilation shows that the working version

contains the following snippet:

unsigned long int _sizeof_S1A_Y1T_ = 1;
unsigned long int _alignof_S1A_Y1T_ = 1;
__attribute__ ((aligned(8))) char _buf22[_sizeof_S1A_Y1T_];

whereas in the broken version, the same region of code is missing the first two lines, thus resulting in an undeclared identifier error

__attribute__ ((aligned(8))) char _buf22[_sizeof_S1A_Y1T_];