Deprecate with type operator in 3.4

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -42,7 +42,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   /** mods object name impl */
   case class ModuleDef(name: TermName, impl: Template)(implicit @constructorOnly src: SourceFile)
     extends MemberDef {
-    type ThisTree[+T <: Untyped] <: Trees.NameTree[T] with Trees.MemberDef[T] with ModuleDef
+    type ThisTree[+T <: Untyped] <: Trees.NameTree[T] & Trees.MemberDef[T] & ModuleDef
     def withName(name: Name)(using Context): ModuleDef = cpy.ModuleDef(this)(name.toTermName, impl)
   }
 

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

@@ -12,7 +12,7 @@ import scala.PartialFunction.cond
 
 trait CliCommand:
 
-  type ConcreteSettings <: CommonScalaSettings with Settings.SettingGroup
+  type ConcreteSettings <: CommonScalaSettings & Settings.SettingGroup
 
   def versionMsg: String
 

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1756,12 +1756,14 @@ object Parsers {
         if in.token == LBRACE || in.token == INDENT then
           t
         else
-          report.errorOrMigrationWarning(
-            DeprecatedWithOperator(rewriteNotice(`future-migration`)),
-            in.sourcePos(withOffset),
-            from = future)
-          if sourceVersion == `future-migration` then
-            patch(source, Span(withOffset, withOffset + 4), "&")
+          val withSpan = Span(withOffset, withOffset + 4)
+          report.gradualErrorOrMigrationWarning(
+            DeprecatedWithOperator(rewriteNotice(`3.4-migration`)),
+            source.atSpan(withSpan),
+            warnFrom = `3.4`,
+            errorFrom = future)
+          if sourceVersion.isAtLeast(`3.4-migration`) then
+            patch(source, withSpan, "&")
           atSpan(startOffset(t)) { makeAndType(t, withType()) }
       else t
 

compiler/test-resources/repl/i6643

@@ -1,7 +1,12 @@
 scala> import scala.collection._
-
 scala>:type 1
 Int
-
 scala> object IterableTest { def g[CC[_] <: Iterable[_] with IterableOps[_, _, _]](from: CC[Int]): IterableFactory[CC] = ??? }
+1 warning found
+-- [E003] Syntax Warning: ------------------------------------------------------
+1 | object IterableTest { def g[CC[_] <: Iterable[_] with IterableOps[_, _, _]](from: CC[Int]): IterableFactory[CC] = ??? }
+  |                                                  ^^^^
+  |                with as a type operator has been deprecated; use & instead
+  |
+  | longer explanation available when compiling with `-explain`
 // defined object IterableTest

compiler/test-resources/type-printer/infix

@@ -48,10 +48,31 @@ def foo: Int && Boolean & String
 scala> def foo: Int && (Boolean & String) = ???
 def foo: Int && (Boolean & String)
 scala> def foo: Int && (Boolean with String) = ???
+1 warning found
+-- [E003] Syntax Warning: ------------------------------------------------------
+1 | def foo: Int && (Boolean with String) = ???
+  |                          ^^^^
+  |                with as a type operator has been deprecated; use & instead
+  |
+  | longer explanation available when compiling with `-explain`
 def foo: Int && (Boolean & String)
 scala> def foo: (Int && Boolean) with String = ???
+1 warning found
+-- [E003] Syntax Warning: ------------------------------------------------------
+1 | def foo: (Int && Boolean) with String = ???
+  |                           ^^^^
+  |                with as a type operator has been deprecated; use & instead
+  |
+  | longer explanation available when compiling with `-explain`
 def foo: Int && Boolean & String
 scala> def foo: Int && Boolean with String = ???
+1 warning found
+-- [E003] Syntax Warning: ------------------------------------------------------
+1 | def foo: Int && Boolean with String = ???
+  |                         ^^^^
+  |                with as a type operator has been deprecated; use & instead
+  |
+  | longer explanation available when compiling with `-explain`
 def foo: Int && (Boolean & String)
 scala> def foo: Int && Boolean | String = ???
 def foo: Int && Boolean | String

tests/neg/i2887b.scala

@@ -4,7 +4,7 @@ trait C { type M <: B }
 trait D { type M >: A }
 
 object Test {
-  def test(x: C with D): Unit = {
+  def test(x: C & D): Unit = {
     def foo(a: A, b: B)(z: a.S[b.I,a.I][b.S[a.I,a.I]]) = z
     def bar(a: A, y: x.M) = foo(a,y)
     def baz(a: A) = bar(a, a)

tests/neg/i8736.scala

@@ -14,13 +14,13 @@ object App extends App {
   def field[V](s: String)(v: V): Rec[s.type, V] = Rec0(Map(s -> v)).asInstanceOf[Rec[s.type, V]]
 
   implicit class RecOps[R <: Rec0[_]](has: R) {
-    def +[K1 <: String, V1](that: Rec[K1, V1]): R with Rec[K1, V1] = Rec0(has.map ++ that.map).asInstanceOf[R with Rec[K1, V1]]
+    def +[K1 <: String, V1](that: Rec[K1, V1]): R & Rec[K1, V1] = Rec0(has.map ++ that.map).asInstanceOf[R with Rec[K1, V1]]
   }
 
   def rec:
     Rec["k", String]
-      with Rec["v", Int]
-      with Rec["z", Boolean]
+      & Rec["v", Int]
+      & Rec["z", Boolean]
     = {
     field("k")("Str") +
       field("v")(0) +

tests/neg/with-type-operator-future-migration.check

@@ -1,7 +1,7 @@
 -- [E003] Syntax Error: tests/neg/with-type-operator-future-migration.scala:5:13 ---------------------------------------
 5 |def foo: Int with String = ??? // error
-  |             ^
+  |             ^^^^
   |             with as a type operator has been deprecated; use & instead
-  |             This construct can be rewritten automatically under -rewrite -source future-migration.
+  |             This construct can be rewritten automatically under -rewrite -source 3.4-migration.
   |
   | longer explanation available when compiling with `-explain`

tests/pos-deep-subtype/3324h.scala

@@ -1,5 +1,7 @@
 //> using options -Xfatal-warnings
 
+import scala.language.`3.3`
+
 object Test {
   trait Marker
   def foo[T](x: T) = x match {
@@ -8,7 +10,7 @@ object Test {
   }
 
   def foo2[T](x: T) = x match {
-    case _: T with Marker      => // scalac emits a warning
+    case _: T with Marker      => // scalac or 3.4 emits a warning
     case _ =>
   }
 }

tests/pos/with-type-operator-3.3.scala

@@ -0,0 +1,5 @@
+//> using options -Werror
+
+import scala.language.`3.3`
+
+def foo: Int with String = ???

tests/pos/with-type-operator.scala → tests/pos/with-type-operator-3.4-migration.scala

@@ -1,3 +1,3 @@
-//> using options -Werror
+import scala.language.`3.4-migration`
 
 def foo: Int with String = ??? // warn