A purity change

[bearophile]

This used to compile (probably dmd 2.060):


struct Foo {
     immutable int y;
     void bar(TF)(TF f) pure {
         f(1);
     }
     void spam() pure {
         bar((int x) => y);
     }
}
void main() {}


But now it gives:

test.d(4): Error: pure function 'test.Foo.bar!(immutable(int) 
delegate(int x) nothrow @safe).bar' cannot call impure delegate 
'f'
test.d(7): Error: template instance test.Foo.bar!(immutable(int) 
delegate(int x) nothrow @safe) error instantiating

Is it a correct error?

Bye,
bearophile