Enable stricter pattern binding warnings by default

compiler/src/dotty/tools/dotc/config/Feature.scala

@@ -90,7 +90,7 @@ object Feature:
    */
   def warnOnMigration(msg: Message, pos: SrcPos, version: SourceVersion)(using Context): Boolean =
     if sourceVersion.isMigrating && sourceVersion.stable == version
-       || (version == `3.0` || version == `3.1` || version == `3.2`) && migrateTo3
+       || (version == `3.0` || version == `3.1`) && migrateTo3
     then
       report.migrationWarning(msg, pos)
       true

compiler/src/dotty/tools/dotc/config/SourceVersion.scala

@@ -17,6 +17,10 @@ enum SourceVersion:
 
   def isAtLeast(v: SourceVersion) = stable.ordinal >= v.ordinal
 
+  def isBetween(low: SourceVersion, high: SourceVersion): Boolean =
+    require(low.ordinal < high.ordinal)
+    isAtLeast(low) && stable.ordinal <= high.ordinal
+
 object SourceVersion extends Property.Key[SourceVersion]:
   def defaultSourceVersion = `3.2`
 

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

@@ -1619,7 +1619,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
             tree.selector.removeAttachment(desugar.CheckIrrefutable) match {
               case Some(checkMode) if !sel.tpe.hasAnnotation(defn.UncheckedAnnot) =>
                 val isPatDef = checkMode == desugar.MatchCheck.IrrefutablePatDef
-                if !checkIrrefutable(sel, pat, isPatDef) && sourceVersion.isAtLeast(`3.2`) && sourceVersion.isMigrating then
+                if !checkIrrefutable(sel, pat, isPatDef)
+                  && sourceVersion.isMigrating
+                  && sourceVersion.isBetween(`3.2`, `future`)
+                then
                   if isPatDef then uncheckedBrackets(tree.selector) match
                     case None =>
                       patch(Span(tree.selector.span.end), ": @unchecked")

docs/_docs/reference/language-versions/source-compatibility.md

@@ -6,20 +6,23 @@ movedTo: https://docs.scala-lang.org/scala3/reference/language-versions.html
 
 Scala 3 does NOT guarantee source compatibility between different minor language versions (e.g. some syntax valid in 3.x might get deprecated and then phased out in 3.y for y > x). There are also some syntax structures that were valid in Scala 2 but are not anymore in Scala 3. However the compiler provides a possibility to specify the desired version of syntax used in a particular file or globally for a run of the compiler to make migration between versions easier.
 
-The default Scala language syntax version currently supported by the Dotty compiler is [`3.0`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/0$.html). There are also other language versions that can be specified instead:
+The default Scala language syntax version currently supported by the Dotty compiler is [`3.2`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/2$.html). There are also other language versions that can be specified instead:
 
-- [`3.0-migration`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/0-migration$.html): Same as `3.0` but with a Scala 2 compatibility mode that helps moving Scala 2.13 sources over to Scala 3. In particular, it
+- [`3.0-migration`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/0-migration$.html): Same as
+`3.0` and `3.1`, but with a Scala 2 compatibility mode that helps moving Scala 2.13 sources over to Scala 3. In particular, it
 
     - flags some Scala 2 constructs that are disallowed in Scala 3 as migration warnings instead of hard errors,
     - changes some rules to be more lenient and backwards compatible with Scala 2.13
     - gives some additional warnings where the semantics has changed between Scala 2.13 and 3.0
     - in conjunction with `-rewrite`, offer code rewrites from Scala 2.13 to 3.0.
 
-- [`future`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$future$.html): A preview of changes introduced in the next versions after 3.0. In the doc pages here we refer to the language version with these changes as `3.1`, but it might be that some of these changes will be rolled out in later `3.x` versions.
+- [`3.0`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/0$.html), [`3.1`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/1$.html): the default set of features included in scala versions `3.0.0` to `3.1.3`.
+- [`3.2`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/2$.html): the same as `3.0` and `3.1`, but [stricter pattern bindings](https://docs.scala-lang.org/scala3/reference/changed-features/pattern-bindings.html) are now enabled (part of `future` in earlier `3.x` releases), producing warnings for refutable patterns. These warnings can be silenced to achieve the same runtime behavior, but in `future` they become errors and refutable patterns will not compile.
+- [`3.2-migration`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$3/2-migration$.html): the same as `3.2`, but in conjunction with `-rewrite`, offer code rewrites from Scala `3.0/3.1` to `3.2`.
+- [`future`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$future$.html): A preview of changes that will be introduced in `3.x` versions after `3.2`.
+Some Scala 2 specific idioms are dropped in this version. The feature set supported by this version may grow over time as features become stabilised for preview.
 
-Some Scala 2 specific idioms will be dropped in this version. The feature set supported by this version will be refined over time  as we approach its release.
-
-- [`future-migration`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$future-migration$.html): Same as `future` but with additional helpers to migrate from `3.0`. Similarly to the helpers available under `3.0-migration`, these include migration warnings and optional rewrites.
+- [`future-migration`](https://scala-lang.org/api/3.x/scala/runtime/stdLibPatches/language$$future-migration$.html): Same as `future` but with additional helpers to migrate from `3.2`. Similarly to the helpers available under `3.0-migration`, these include migration warnings and optional rewrites.
 
 There are two ways to specify a language version :