Convert more conditional given instances to new syntax

Author: odersky

docs/docs/reference/contextual/delegates.md

@@ -18,7 +18,7 @@ given intOrd: Ord[Int] {
     if (x < y) -1 else if (x > y) +1 else 0
 }
 
-given listOrd[T](given ord: Ord[T]): Ord[List[T]] {
+given listOrd[T]: (ord: Ord[T]) => Ord[List[T]] {
 
   def compare(xs: List[T], ys: List[T]): Int = (xs, ys) match {
     case (Nil, Nil) => 0
@@ -33,16 +33,18 @@ given listOrd[T](given ord: Ord[T]): Ord[List[T]] {
 This code defines a trait `Ord` with two given instances. `intOrd` defines
 a given for the type `Ord[Int]` whereas `listOrd[T]` defines givens
 for `Ord[List[T]]` for all types `T` that come with a given instance for `Ord[T]` themselves.
-The `(given ord: Ord[T])` clause in `listOrd` defines an implicit parameter.
-Given clauses are further explained in the [next section](./given-clauses.md).
+The `(ord: Ord[T]) =>` clause in `listOrd` defines a condition: There must be a
+given instance of type `Ord[T]` so that a given instance of type `List[Ord[T]]` can
+be synthesized. Such conditions are expanded by the compiler to implicit
+parameters, which are explained in the [next section](./given-clauses.md).
 
 ## Anonymous Given Instances
 
 The name of a given instance can be left out. So the definitions
 of the last section can also be expressed like this:
 ```scala
 given Ord[Int] { ... }
-given [T](given Ord[T]): Ord[List[T]] { ... }
+given [T]: Ord[T] => Ord[List[T]] { ... }
 ```
 If the name of a given is missing, the compiler will synthesize a name from
 the implemented type(s).
@@ -61,7 +63,7 @@ returned for this and all subsequent accesses to `global`.
 Alias givens can be anonymous, e.g.
 ```scala
 given Position = enclosingTree.position
-given (given outer: Context): Context = outer.withOwner(currentOwner)
+given (outer: Context) => Context = outer.withOwner(currentOwner)
 ```
 An alias given can have type parameters and given clauses just like any other given instance, but it can only implement a single type.
 

docs/docs/reference/contextual/derivation.md

@@ -312,7 +312,7 @@ In this case the code that is generated by the inline expansion for the derived
 following, after a little polishing,
 
 ```scala
-given derived$Eq[T](given eqT: Eq[T]): Eq[Opt[T]] =
+given derived$Eq[T]: (eqT: Eq[T]) => Eq[Opt[T]] =
   eqSum(summon[Mirror[Opt[T]]],
     List(
       eqProduct(summon[Mirror[Sm[T]]], List(summon[Eq[T]]))
@@ -329,13 +329,13 @@ As a third example, using a higher level library such as shapeless the type clas
 `derived` method as,
 
 ```scala
-given eqSum[A](given inst: => K0.CoproductInstances[Eq, A]): Eq[A] {
+given eqSum[A] (inst: => K0.CoproductInstances[Eq, A]) => Eq[A] {
   def eqv(x: A, y: A): Boolean = inst.fold2(x, y)(false)(
     [t] => (eqt: Eq[t], t0: t, t1: t) => eqt.eqv(t0, t1)
   )
 }
 
-given eqProduct[A](given inst: K0.ProductInstances[Eq, A]): Eq[A] {
+given eqProduct[A] (inst: K0.ProductInstances[Eq, A]) => Eq[A] {
   def eqv(x: A, y: A): Boolean = inst.foldLeft2(x, y)(true: Boolean)(
     [t] => (acc: Boolean, eqt: Eq[t], t0: t, t1: t) => Complete(!eqt.eqv(t0, t1))(false)(true)
   )

docs/docs/reference/contextual/implicit-by-name-parameters.md

@@ -12,7 +12,7 @@ trait Codec[T] {
 
 given intCodec: Codec[Int] = ???
 
-given optionCodec[T](given ev: => Codec[T]): Codec[Option[T]] {
+given optionCodec[T]: (ev: => Codec[T]) => Codec[Option[T]] {
   def write(xo: Option[T]) = xo match {
     case Some(x) => ev.write(x)
     case None =>

tests/pos/combine.scala

@@ -2,7 +2,7 @@ trait Semigroup[A] {
   def (x: A) combine (y: A): A
 }
 given Semigroup[Int] = ???
-given [A, B](given Semigroup[A], Semigroup[B]): Semigroup[(A, B)]  = ???
+given [A, B]: Semigroup[A], Semigroup[B] => Semigroup[(A, B)]  = ???
 object Test extends App {
   ((1, 1)) combine ((2, 2)) // doesn't compile
   ((1, 1): (Int, Int)) combine (2, 2) // compiles

tests/run/implied-specifity-2.scala

@@ -35,9 +35,9 @@ given Arg
 
 class Bam(val str: String)
 
-given lo(given Low): Bam("lo")
+given lo: Low => Bam("lo")
 
-given hi(given High)(given Arg): Bam("hi")
+given hi: High => Arg => Bam("hi")
 
 class Bam2(val str: String)