On Tue, 20 Jul 2010 16:19:50 +0000, dsimcha wrote: > Bug 2594 (http://d.puremagic.com/issues/show_bug.cgi?id=2594) has > languished in Bugzilla for about 1.5 years and really irks me. > Furthermore, std.math.pow(), for example, doesn't work when passed > immutable values. In other words, right now you can't do: > > immutable uint foo = 5; > immutable uint bar = 2; > uint baz = foo ^^ bar; > > Lots of functions in Phobos, as well as libs I've written, have > basically this bug, and fixing/preventing all instances of it is a > monumental and tedious task. > > Therefore, I propose that implicit function template instantiation > automatically runs the equivalent of a shallow Unqual on its non-ref > arguments before determining the types. In other words, if a > const/immutable object could be implicitly cast to shallow mutable, it > is. For example: > > void fun(T, U)(T arg1, U arg2) { > // Do stuff that assumes arg1, arg2 are shallowly mutable. > } > > void main() { > immutable uint foo = 3; > immutable char[] bar = "bar"; > > // This instantiates fun with T = uint and U = // immutable(char)[], > NOT T = immutable uint and // U = immutable char[]. > fun(foo, bar); > } > > This would prevent a lot of nasty bugs but would be safe because > arguments passed by value are shallowly copied and therefore can safely > be made shallowly mutable, which is why implicitly casting between fully > const/immutable and shallowly mutable is allowed already by the spec.
++vote -Lars
