Delay priority change until 3.7

Warnings from 3.6, change in 3.7. This is one version later than
originally planned.

Author: odersky

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -1767,7 +1767,7 @@ trait Applications extends Compatibility {
                       // and in mode Scala3-migration when we compare with the old Scala 2 rules.
 
     case Intermediate // Intermediate rules: better means specialize, but map all type arguments downwards
-                      // These are enabled for 3.0-3.4, or if OldImplicitResolution
+                      // These are enabled for 3.0-3.5, or if OldImplicitResolution
                       // is specified, and also for all comparisons between old-style implicits,
 
     case New          // New rules: better means generalize, givens (and extensions) always beat implicits
@@ -1803,7 +1803,7 @@ trait Applications extends Compatibility {
       val oldResolution = ctx.mode.is(Mode.OldImplicitResolution)
       if !preferGeneral || Feature.migrateTo3 && oldResolution then
         CompareScheme.Old
-      else if Feature.sourceVersion.isAtMost(SourceVersion.`3.4`)
+      else if Feature.sourceVersion.isAtMost(SourceVersion.`3.5`)
         || oldResolution
         || alt1.symbol.is(Implicit) && alt2.symbol.is(Implicit)
       then CompareScheme.Intermediate
@@ -1869,7 +1869,7 @@ trait Applications extends Compatibility {
      *     available in 3.0-migration if mode `Mode.OldImplicitResolution` is turned on as well.
      *     It is used to highlight differences between Scala 2 and 3 behavior.
      *
-     *   - In Scala 3.0-3.5, the behavior is as follows: `T <:p U` iff there is an implicit conversion
+     *   - In Scala 3.0-3.6, the behavior is as follows: `T <:p U` iff there is an implicit conversion
      *     from `T` to `U`, or
      *
      *        flip(T) <: flip(U)
@@ -1884,14 +1884,14 @@ trait Applications extends Compatibility {
      *     of parameters are not affected. So `T <: U` would imply `Set[Cmp[U]] <:p Set[Cmp[T]]`,
      *     as usual, because `Set` is non-variant.
      *
-     *   - From Scala 3.6, `T <:p U` means `T <: U` or `T` convertible to `U`
+     *   - From Scala 3.7, `T <:p U` means `T <: U` or `T` convertible to `U`
      *     for overloading resolution (when `preferGeneral is false), and the opposite relation
      *     `U <: T` or `U convertible to `T` for implicit disambiguation between givens
-     *     (when `preferGeneral` is true). For old-style implicit values, the 3.4 behavior is kept.
+     *     (when `preferGeneral` is true). For old-style implicit values, the 3.5 behavior is kept.
      *     If one of the alternatives is an implicit and the other is a given (or an extension), the implicit loses.
      *
-     *   - In Scala 3.5 and Scala 3.6-migration, we issue a warning if the result under
-     *     Scala 3.6 differ wrt to the old behavior up to 3.5.
+     *   - In Scala 3.6 and Scala 3.7-migration, we issue a warning if the result under
+     *     Scala 3.7 differs wrt to the old behavior up to 3.6.
      *
      *  Also and only for given resolution: If a compared type refers to a given or its module class, use
      *  the intersection of its parent classes instead.

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -1305,26 +1305,26 @@ trait Implicits:
     /** Search a list of eligible implicit references */
     private def searchImplicit(eligible: List[Candidate], contextual: Boolean): SearchResult =
 
-      // A map that associates a priority change warning (between -source 3.4 and 3.6)
+      // A map that associates a priority change warning (between -source 3.6 and 3.7)
       // with the candidate refs mentioned in the warning. We report the associated
       // message if one of the critical candidates is part of the result of the implicit search.
       val priorityChangeWarnings = mutable.ListBuffer[(/*critical:*/ List[TermRef], Message)]()
 
       def isWarnPriorityChangeVersion(sv: SourceVersion): Boolean =
-        sv.stable == SourceVersion.`3.5` || sv == SourceVersion.`3.6-migration`
+        sv.stable == SourceVersion.`3.6` || sv == SourceVersion.`3.7-migration`
 
       /** Compare `alt1` with `alt2` to determine which one should be chosen.
        *
        *  @return  a number > 0   if `alt1` is preferred over `alt2`
        *           a number < 0   if `alt2` is preferred over `alt1`
        *           0              if neither alternative is preferred over the other
        *  The behavior depends on the source version
-       *      before 3.5: compare with preferGeneral = false
-       *             3.5: compare twice with preferGeneral = false and true, warning if result is different,
+       *      before 3.6: compare with preferGeneral = false
+       *             3.6: compare twice with preferGeneral = false and true, warning if result is different,
        *                  return old result with preferGeneral = false
-       *   3.6-migration: compare twice with preferGeneral = false and true, warning if result is different,
+       *   3.7-migration: compare twice with preferGeneral = false and true, warning if result is different,
        *                  return new result with preferGeneral = true
-       *  3.6 and higher: compare with preferGeneral = true
+       *  3.7 and higher: compare with preferGeneral = true
        *
        *  @param disambiguate      The call is used to disambiguate two successes, not for ranking.
        *                           When ranking, we are always filtering out either > 0 or <= 0 results.
@@ -1348,15 +1348,15 @@ trait Implicits:
                 case -1 => "the second alternative"
                 case  1 => "the first alternative"
                 case _  => "none - it's ambiguous"
-              if sv.stable == SourceVersion.`3.5` then
+              if sv.stable == SourceVersion.`3.6` then
                 warn(
                   em"""Given search preference for $pt between alternatives
                       |  ${alt1.ref}
                       |and
                       |  ${alt2.ref}
                       |will change.
                       |Current choice           : ${choice(prev)}
-                      |New choice from Scala 3.6: ${choice(cmp)}""")
+                      |New choice from Scala 3.7: ${choice(cmp)}""")
                 prev
               else
                 warn(
@@ -1366,7 +1366,7 @@ trait Implicits:
                       |  ${alt2.ref}
                       |has changed.
                       |Previous choice          : ${choice(prev)}
-                      |New choice from Scala 3.6: ${choice(cmp)}""")
+                      |New choice from Scala 3.7: ${choice(cmp)}""")
                 cmp
             else cmp max prev
               // When ranking, we keep the better of cmp and prev, which ends up retaining a candidate

tests/neg/ctx-bounds-priority.scala

@@ -1,4 +1,4 @@
-//> using options -source 3.6
+//> using options -source 3.7
 trait Eq[A]
 trait Order[A] extends Eq[A]:
   def toOrdering: Ordering[A]

tests/neg/given-triangle.check

@@ -9,4 +9,4 @@
    |  (given_B : B)
    |will change.
    |Current choice           : the second alternative
-   |New choice from Scala 3.6: the first alternative
+   |New choice from Scala 3.7: the first alternative

tests/neg/given-triangle.scala

@@ -1,4 +1,4 @@
-//> using options -source 3.5
+//> using options -source 3.6
 class A
 class B extends A
 class C extends A

tests/neg/i15264.scala

@@ -1,4 +1,4 @@
-import language.`3.6`
+import language.`3.7`
 object priority:
     // lower number = higher priority
     class Prio0 extends Prio1

tests/neg/i21212.scala

@@ -1,4 +1,4 @@
-
+//> using options -source 3.7
 object Minimization:
 
   trait A

tests/neg/i21303/Test.scala

@@ -1,4 +1,4 @@
-//> using options -source 3.6-migration
+//> using options -source 3.7-migration
 import scala.deriving.Mirror
 import scala.compiletime.*
 import scala.reflect.ClassTag

tests/run/given-triangle.scala

@@ -1,4 +1,4 @@
-import language.`3.6`
+import language.`3.7`
 
 class A
 class B extends A

tests/run/implicit-specifity.scala

@@ -1,4 +1,4 @@
-import language.`3.6`
+import language.`3.7`
 
 case class Show[T](val i: Int)
 object Show {

tests/run/implied-priority.scala

@@ -1,6 +1,6 @@
 /* These tests show various mechanisms available for implicit prioritization.
  */
-import language.`3.6`
+import language.`3.7`
 
 class E[T](val str: String)  // The type for which we infer terms below
 

tests/warn/i20420.scala

@@ -1,4 +1,4 @@
-//> using options -source 3.5-migration
+//> using options -source 3.6-migration
 
 final class StrictEqual[V]
 final class Less[V]

tests/warn/i21036a.check

@@ -7,4 +7,4 @@
   |                   (a : A)
   |                 will change.
   |                 Current choice           : the first alternative
-  |                 New choice from Scala 3.6: the second alternative
+  |                 New choice from Scala 3.7: the second alternative

tests/warn/i21036a.scala

@@ -1,4 +1,4 @@
-//> using options -source 3.5
+//> using options -source 3.6
 trait A
 trait B extends A
 given b: B = ???

tests/warn/i21036b.check

@@ -7,4 +7,4 @@
   |                   (a : A)
   |                 has changed.
   |                 Previous choice          : the first alternative
-  |                 New choice from Scala 3.6: the second alternative
+  |                 New choice from Scala 3.7: the second alternative

tests/warn/i21036b.scala

@@ -1,4 +1,4 @@
-//> using options -source 3.6-migration
+//> using options -source 3.7-migration
 trait A
 trait B extends A
 given b: B = ???