IFTI undefined identifier confusion

[sampotter]

Here's a small sample:

struct A(int M, int N) {}

void f(int M)(A!(M - 1, M) a) {}

void main() {
     A!(1, 2) a;
     f(a);
}

Output from dmd:

test.d(3): Error: undefined identifier `M`
test.d(7): Error: template `f` is not callable using argument types `!()(A!(1, 2))`
test.d(3):        Candidate is: `f(int M)(A!(M - 1, M) a)`

Note the first line of output. It seems like the compiler should be smart enough to understand that every instance of the identifier M is defined on that line.