No boxing here.

noboxing

import com.azavea.math.Numeric
import com.azavea.math.EasyImplicits._

class Blah {
 def blah[@specialized T:Numeric:Manifest, @specialized W:Numeric:Manifest](f:Function1[T,W]):W  = {
  f(numeric[T].zero)
}
 def blah2[T:Numeric:Manifest](f:Function[T,T]):T = {
    f(numeric[T].zero)
}
}


javap -verbose Blah 

 public int blah$mIIc$sp(scala.Function1, com.azavea.math.Numeric, scala.reflect.Manifest, com.azavea.math.Numeric, scala.reflect.Manifest);
  Code:
   Stack=3, Locals=6, Args_size=6
   0:	aload_1
   1:	getstatic	#12; //Field com/azavea/math/EasyImplicits$.MODULE$:Lcom/azavea/math/EasyImplicits$;
   4:	aload_2
   5:	invokevirtual	#156; //Method com/azavea/math/EasyImplicits$.numeric$mIc$sp:(Lcom/azavea/math/Numeric;)Lcom/azavea/math/Numeric;
   8:	invokeinterface	#160,  1; //InterfaceMethod com/azavea/math/Numeric.zero$mcI$sp:()I
   13:	invokeinterface	#181,  2; //InterfaceMethod scala/Function1.apply$mcII$sp:(I)I
   18:	ireturn
  LineNumberTable: 
   line 66: 0

  LocalVariableTable: 
   Start  Length  Slot  Name   Signature
   0      19      0    this       Lmarc/junk/Blah;
   0      19      1    f       Lscala/Function1;
   0      19      2    evidence$15       Lcom/azavea/math/Numeric;
   0      19      3    evidence$16       Lscala/reflect/Manifest;
   0      19      4    evidence$17       Lcom/azavea/math/Numeric;
   0      19      5    evidence$18       Lscala/reflect/Manifest;

  Signature: length = 0x2
   00 77 

public long blah$mIJc$sp(scala.Function1, com.azavea.math.Numeric, scala.reflect.Manifest, com.azavea.math.Numeric, scala.reflect.Manifest);
  Code:
   Stack=3, Locals=6, Args_size=6
   0:	aload_1
   1:	getstatic	#12; //Field com/azavea/math/EasyImplicits$.MODULE$:Lcom/azavea/math/EasyImplicits$;
   4:	aload_2
   5:	invokevirtual	#156; //Method com/azavea/math/EasyImplicits$.numeric$mIc$sp:(Lcom/azavea/math/Numeric;)Lcom/azavea/math/Numeric;
   8:	invokeinterface	#160,  1; //InterfaceMethod com/azavea/math/Numeric.zero$mcI$sp:()I
   13:	invokeinterface	#186,  2; //InterfaceMethod scala/Function1.apply$mcJI$sp:(I)J
   18:	lreturn