Better handling of implicits over numeric types.

Compiling scala.math.BigDecimal and scala.math.BigInteger shows a problem.
The conversion `int2bigInt` is not applicable to a Byte because `Byte -> Int`
requires another implicit conversion.

We fix that by using a new method relaxed_<:< for implicit compatibility checks,
which always admits numeric widenings.

This leads to another problem. Now the conversions

    implicit def byteToInt(x: Byte): Int
    implicit def byteToShort(x: Byte): Short

are ambiguous when we try to convert from Byte to Int.
We fix that by adding a "tie-break" to implicit search
where if several methods match a numeric value result type
and all have numeric value types as result types, we
pick the numerically largest type that matches.

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/pos/implicits1.scala b/tests/pos/implicits1.scala
index d8ca76de5..eda134663 100644
--- a/tests/pos/implicits1.scala
+++ b/tests/pos/implicits1.scala
@@ -36,6 +36,8 @@ object Implicits {
 
   val d: Int = z.foo("abc")
 
+  val x: X = Byte.MinValue
+
   //import X.BarDeco
 
   println(z.bar)
@@ -50,4 +52,6 @@ object Implicits {
 
   val s: Modifier = Some("rd").getOrElse("")
 
+  val xx: Int = (1: Byte)
+
 }