compiler errors - Strange behaviour with for loop and range: found :Int required: scala.collection.generic.CanBuildFrom[Nothing,String,?] -

i bizarre because following code compiled long long time without complaint nor comment.

val depth = dbstuff.lookupsomeint(blah, blah) (x: int <- 0 depth) {  dostuffwith(x).ornot } 

and yet today did not compile on 1 of machines (while still compiling on another)

here error:

[error] /users/someone/somepath/somefile.scala:415: type mismatch; [error]  found   : int [error]  required: scala.collection.generic.canbuildfrom[nothing,string,?] [error]           (x: int <- 0 depth) { [error]                               ^ [error] 1 error found 

further food chain did add val:

  protected implicit val columnorderbylist = seq.empty[seq[string]] 

this change i'm aware of , error occurred after addition.

the fix appears be:

   (x: int <- range(0, depth, 1)) {      dostuffwith(x).ornot    } 

it refused other attempts "range" work: e.g. (0 depth) in brackets etc.

hate out load errors scare crap out of me. happen if 500 compile errors instead of 1? or if "fix" didn't become self-evident? worse yet if root cause wasn't self evident back-out wasn't possible?

i'm sure genius knows happened here , why have no real idea how find out (as in paths follow) figure out on lonesome...

light welcome!

comfirmed: remove protected implicit val columnorderbylist , original code compiles no problem -- place in , error documented. food chain mean val in class inherited class has compile error val in scope.

this 1 of problem happen when many implicit conversions in scope.

scala> 0 3 res0: scala.collection.immutable.range.inclusive = range(0, 1, 2, 3) 

is equivalent to

scala> intwrapper(0) 3 res1: scala.collection.immutable.range.inclusive = range(0, 1, 2, 3) 

however,

scala> implicit val s: seq[seq[string]] = null s: seq[seq[string]] = null  scala> 0 3 <console>:12: error: type mismatch;  found   : int(3)  required: scala.collection.generic.canbuildfrom[nothing,string,?]        0 3             ^ 

is equivalent

scala> s(0) 3 <console>:12: error: type mismatch;  found   : int(3)  required: scala.collection.generic.canbuildfrom[nothing,string,?]        s(0) 3                ^  scala> s.apply(0) 3 <console>:12: error: type mismatch;  found   : int(3)  required: scala.collection.generic.canbuildfrom[nothing,string,?]        s.apply(0) 3                      ^ 

your newly introduced implicit values has higher preference predefined one, therefore chosen. normally, shouldn't problem, in case seq defines method to, can convert collection collection of different type. full signature def to[col[_]](implicit cbf: canbuildfrom[nothing, a, col[a]]): col[a], explains error message expected canbuildfrom.

lection: minimize scope of implicits far possible.