Fix #22794: Emit the definition of Arrays.newArray even though it's a primitive.

compiler/src/dotty/tools/backend/sjs/JSCodeGen.scala

@@ -1557,7 +1557,7 @@ class JSCodeGen()(using genCtx: Context) {
 
       def jsParams = params.map(genParamDef(_))
 
-      if (primitives.isPrimitive(sym)) {
+      if (primitives.isPrimitive(sym) && sym != defn.newArrayMethod) {
         None
       } else if (sym.is(Deferred) && currentClassSym.isNonNativeJSClass) {
         // scala-js/#4409: Do not emit abstract methods in non-native JS classes

sbt-test/scalajs/backward-compat/build.sbt

@@ -0,0 +1,5 @@
+enablePlugins(ScalaJSPlugin)
+
+scalaVersion := sys.props("plugin.scalaVersion")
+
+libraryDependencies += "org.scalameta" %%% "munit" % "1.1.0"

sbt-test/scalajs/backward-compat/project/plugins.sbt

@@ -0,0 +1,2 @@
+
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % sys.props("plugin.scalaJSVersion"))

sbt-test/scalajs/backward-compat/src/test/scala/NewArrayIssue22794Test.scala

@@ -0,0 +1,5 @@
+class NewArrayIssue22794Test extends munit.FunSuite {
+  test("foo") {
+    assert(2 + 2 == 4)
+  }
+}

sbt-test/scalajs/backward-compat/test

@@ -0,0 +1 @@
+> test