At the moment the grammar misses a case where a user-defined function 
returns a structure. Specifically, the grammar does not permit 
initialization of the structure members.

The following code should reproduce this issue:


structure Vector : (real(X), real(Y), real(Z))

infix(plus)

plus : (Vector(left), Vector(right)) -> (Vector(result, 0.0, 0.0, 0.0))
{
	result.X = left.X + right.X
	result.Y = left.Y + right.Y
	result.Z = left.Z + right.Z
}


entrypoint : () -> ()
{
	Vector(a, 1.0, 1.0, 1.0)
	Vector(b, 2.0, 2.0, 2.0)

	Vector(c, a plus b)
	display(c)
}


display : (Vector(v)) -> ()
{
	debugwritestring(cast(string, v.X))
	debugwritestring(cast(string, v.Y))
	debugwritestring(cast(string, v.Z))
}