Where should I dump workarounds?

[Dukc via Digitalmars-d-learn]

Well, I was working on std.range.chain (I'm new to contributing), 
and when trying to test locally:

...\phobos\std\range>rdmd -unittest -main package
C:\D\dmd2\windows\bin\..\..\src\phobos\std\path.d(1319): Error: 
pure function 'std.path.buildPath!char.buildPath' cannot call 
impure function 'std.path.buildPath!(const(char)[][]).buildPath'
C:\D\dmd2\windows\bin\..\..\src\phobos\std\path.d(1319): Error: 
@safe function 'std.path.buildPath!char.buildPath' cannot call 
@system function 'std.path.buildPath!(const(char)[][]).buildPath'
C:\D\dmd2\windows\bin\..\..\src\phobos\std\path.d(1319): Error: 
function 'std.path.buildPath!(const(char)[][]).buildPath' is not 
nothrow
C:\D\dmd2\windows\bin\..\..\src\phobos\std\path.d(1315): Error: 
nothrow function 'std.path.buildPath!char.buildPath' may throw
package.d(8718): Error: template instance std.path.buildPath!char 
error instantiating

Error in a totally different place! If my code caused this, I 
have no idea how: I haven't touched unittests nor std.path.

Since I don't think you like if my pr (if I manage to even do it) 
contains fixes to other stuff than what I'm trying to do, I 
wonder where I should start patching this. Should I make a new 
branch off master and when done, merge it into the branch I have 
now? Or should I make an entirely new fork?