On Monday, 9 April 2018 at 03:20:58 UTC, helxi wrote:
Is std.variant.visit not @nogc?
These error messages REALLY need to be fixed.
visit, being a template, is @nogc or not based on the arguments
passed to it as well as its own body, so while the error messages
point to visit itself, these are frequently actually caused the
predicate your pass.
....well, in this case, it is actually visit itself.
phobos/std/variant.d(2464): Error: @nogc function
std.variant.visitImpl!(true, VariantN!(8u, int, string), function
(string s) => printf("%s\x0a", cast(immutable(char)*)s), function
(int n) => printf("%i\x0a", n)).visitImpl cannot call non-@nogc
constructor std.variant.VariantException.this
phobos/std/variant.d(2469): Error: @nogc function
std.variant.visitImpl!(true, VariantN!(8u, int, string), function
(string s) => printf("%s\x0a", cast(immutable(char)*)s), function
(int n) => printf("%i\x0a", n)).visitImpl cannot call non-@nogc
function std.variant.VariantN!(8u, int,
string).VariantN.peek!int.peek
phobos/std/variant.d(2469): Error: @nogc function
std.variant.visitImpl!(true, VariantN!(8u, int, string), function
(string s) => printf("%s\x0a", cast(immutable(char)*)s), function
(int n) => printf("%i\x0a", n)).visitImpl cannot call non-@nogc
function std.variant.VariantN!(8u, int,
string).VariantN.peek!string.peek
phobos/std/variant.d(2173): Error: template instance
`std.variant.visitImpl!(true, VariantN!(8u, int, string),
function (string s) => printf("%s\x0a", cast(immutable(char)*)s),
function (int n) => printf("%i\x0a", n))` error instantiating
Ugh, so unreadable even on this level, but at least the actual
information is there:
std.variant.VariantException.this is not marked @nogc (but it
prolly could be)
VariantN.peek is not @nogc because it calls Object.opEquals...
which is broken af, sadly, but can probably be fixed for this
case by marking TypeInfo.opEquals nogc.
I think the peek one is going to be the harder one to work around
since any reimplementation of peek is probably going to still
call it... though MAYBE you can use `!is` instead of `!=`... and
any reimplementation of visit needs to check types.
But if you wanna try to work around it, I would copy the
visitImpl and visit functions out of std.variant and do some
adjustments, then call your version instead (which will be fairly
easy btw since they are already UFCS).
FYI: the way I got these error messages was to go into the Phobos
source and add @nogc to the lowest level template in the
instantiation chain. Then just recompile your program - no need
to recompile Phobos itself since they are templates.
I wish the error messages would just do this for you (simulate
@nogc at the second-highest level) to keep you from having to
edit it yourself just to know what it is.
