This should compile:

void main() {
	int[int] aa;
	foreach(long k, long v; aa) {} // fails on both k and v
		// test.d(3): Error: foreach: index must be type int, not long
		// test.d(3): Error: foreach: value must be type int, not long
	
	static struct OpApply {
		int opApply(int delegate(int)) {return 0;}
	}
	foreach(long x; OpApply()) {} // fails
		// test.d(10): Error: cannot uniquely infer foreach argument types
	
	// In contrast, it does work on plain arrays and ranges:
	
	int[] a;
	foreach(long x; a) {} // ok
	
	static struct Range {
		@property bool empty() {return false;}
		@property int front() {return 0;}
		void popFront() {}
	}
	foreach(long x; Range()) {} // ok
}