Macro expression reuse causes invalid behavior

[darkf]

The following code:

enum T {
    A(int),
    B(float)
}

macro_rules! test(
    ($e:expr) => (
        fn foo(a:T, b:T) -> T {
            match (a, b) {
                (A(x), A(y)) => A($e),
                (B(x), B(y)) => B($e),
                _ => fail!()
            }
        }
    )
)

test!(x + y)

fn main() {
    foo(A(1), A(2));
}

Yields the following type error:

y.rs:18:6: 18:11 error: mismatched types: expected `int` but found `float` (expected int but found float)
y.rs:18 test!(x + y)
              ^~~~~
error: aborting due to previous error

Which is wrong, as the expression should be expanded into both locations, both xs and ys having separate types.

[jdm]

Probably #6000 again.

[huonw]

Seems similar to #8754 too.