Bug 11207 – improve implicit conversions of function pointers/delegates

class A {} class B : A {} B foo(const A) { return null; } void main() { A function(const A) f1 = &foo; // compiles B function(A) f2 = &foo; // does not compile B function(immutable A) f3 = &foo; // does not compile B function(B) f4 = &foo; // does not compile } test.d(6): Error: cannot implicitly convert expression (& foo) of type B function(const(A) _param_0) to B function(A) test.d(7): Error: cannot implicitly convert expression (& foo) of type B function(const(A) _param_0) to B function(immutable(A)) test.d(8): Error: cannot implicitly convert expression (& foo) of type B function(const(A) _param_0) to B function(B) These implicit conversions should be possible. Explicit casting is too confusing and dangerous. If you make a mistake, you will end up with serious runtime errors.

*** This issue has been marked as a duplicate of issue 7725 ***