On Wednesday, 17 February 2016 at 02:51:06 UTC, Walter Bright
wrote:
The trouble with that is you're relying on the programmer to
ensure correctness. It'll revert D to C++ "trust the
programmer" semantics.
You might end up in a worse position than C++, as people will
cast away constness / immutability in third party libraries to
get around the limitations.
C++ added "mutable" keyword for a reason... with head const which
is much less limiting to begin with...
Furthermore, with the current mechanical guarantee of
immutability, it opens up the possibility of relying on such
beyond merely observable behavior - such as immutable data
being placed in ROM, or special GC semantics.
A nonissue.
1. The compiler has access to all reachable types. It can easily
determine if there are reachable types with @mutable fields.
2. This is not a good argument for transitivity of immutability
as head-immutability is sufficient.
