print rewriting checks statements in else bodies too soon

[tsandall]

While playing around with @anderseknert's test assertion experiment I found that print statements are getting checked incorrectly:

package play

assert_equals(a,b) { a == b }
else = false { print(a, "does not equal", b) }

test_foo {
	assert_equals(1, 2)
}

Because the compiler uses WalkBodies on the rule, it's encountering the body of the else statement before it's processed the implicit args of the else statement.