This code: import std.datetime: StopWatch; void main() { StopWatch sw; auto n = sw.peek().nsecs; } Compiled with: dmd -O -release -inline -noboundscheck test.d using DMD 2.056head gives: ...\dmd2\windows\bin\..\..\src\druntime\import\core\time.di(262): Error: template core.time.TickDuration.to(string units,T) if ((units == "seconds" || units == "msecs" || units == "usecs" || units == "hnsecs" || units == "nsecs") && (__traits(isIntegral,T) && T.sizeof >= 4)) does not match any function template declaration ...\dmd2\windows\bin\..\..\src\druntime\import\core\time.di(262): Error: template core.time.TickDuration.to(string units,T) if ((units == "seconds" || units == "msecs" || units == "usecs" || units == "hnsecs" || units == "nsecs") && (__traits(isIntegral,T) && T.sizeof >= 4)) cannot deduce template function from argument types !("seconds",long)()
*** This issue has been marked as a duplicate of issue 6502 ***