Porting from D1 to D2

[ponce via Digitalmars-d-learn]

I have a program that is almost ported from D1 to D2 but there is 
still a problem with a reference to 
object.Throwable.toString(scope void delegate(in string) sink);


With OPTLINK (32-bit):

Error 42: Symbol Undefined 
_D6object9Throwable8toStringMxFMDFxAyaZvZv (const(void 
function(scope void delegate(const(immutable(char)[])))) 
object.Throwable.toString)

With link.exe (64-bit):

vibrant_derelict.lib(exception_311_6db.obj) : error LNK2001: 
unresolved external
  symbol _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_derelict.lib(exception_314_c30.obj) : error LNK2001: 
unresolved external
  symbol _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_derelict.lib(exception_312_89d.obj) : error LNK2001: 
unresolved external
  symbol _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_common2.lib(error_a0_4d3.obj) : error LNK2001: unresolved 
external symbo
l _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_common2.lib(error_9e_2e1.obj) : error LNK2001: unresolved 
external symbo
l _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_common2.lib(error_9f_461.obj) : error LNK2001: unresolved 
external symbo
l _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_derelict.lib(exception_313_a31.obj) : error LNK2001: 
unresolved external
  symbol _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant.obj : error LNK2001: unresolved external symbol 
_D6object9Throwable8toSt
ringMxFMDFxAyaZvZv
vibrant_common2.lib(state_eb9_2ed.obj) : error LNK2001: 
unresolved external symb
ol _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_common2.lib(error_9d_42f.obj) : error LNK2001: unresolved 
external symbo
l _D6object9Throwable8toStringMxFMDFxAyaZvZv
vibrant_common2.lib(error_a1_398.obj) : error LNK2001: unresolved 
external symbo
l _D6object9Throwable8toStringMxFMDFxAyaZvZv
.dub\build\application-debug-windows-x86_64-dmd_2067-A5A845EF2ABB6AC157FC78217DE
83EB9\vibrant.exe : fatal error LNK1120: 1 unresolved externals

I don't quite get what code could be generating that reference, 
since I don't call format or toString on a Throwable.

Anyone has experience with this?