Fix #11592: Scala.js: Handle default params of native JS classes.

They must not be emitted, just like regular methods inside native
JS classes are not emitted.

This ensures that if the default value is `= js.native`, it is not
emitted, and therefore does not report an error tha calling
`js.native` is illegal in non-native code.

Author: sjrd

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

@@ -290,12 +290,12 @@ class JSCodeGen()(using genCtx: Context) {
         "genScalaClass() must be called only for normal classes: "+sym)
     assert(sym.superClass != NoSymbol, sym)
 
-    /*if (hasDefaultCtorArgsAndRawJSModule(sym)) {
-      reporter.error(pos,
-          "Implementation restriction: constructors of " +
-          "Scala classes cannot have default parameters " +
-          "if their companion module is JS native.")
-    }*/
+    if (hasDefaultCtorArgsAndJSModule(sym)) {
+      report.error(
+          "Implementation restriction: " +
+          "constructors of Scala classes cannot have default parameters if their companion module is JS native.",
+          td)
+    }
 
     val classIdent = encodeClassNameIdent(sym)
     val originalName = originalNameOfClass(sym)
@@ -965,9 +965,8 @@ class JSCodeGen()(using genCtx: Context) {
 
     if (hasDefaultCtorArgsAndJSModule(classSym)) {
       report.error(
-          "Implementation restriction: constructors of " +
-          "non-native JS classes cannot have default parameters " +
-          "if their companion module is JS native.",
+          "Implementation restriction: " +
+          "constructors of non-native JS classes cannot have default parameters if their companion module is JS native.",
           classSym.srcPos)
       val ctorDef = js.JSMethodDef(js.MemberFlags.empty,
           js.StringLiteral("constructor"), Nil, None, js.Skip())(
@@ -1067,9 +1066,10 @@ class JSCodeGen()(using genCtx: Context) {
         Some(js.MethodDef(js.MemberFlags.empty, methodName, originalName,
             jsParams, toIRType(patchedResultType(sym)), None)(
             OptimizerHints.empty, None))
-      } else /*if (isJSNativeCtorDefaultParam(sym)) {
+      } else if (sym.isJSNativeCtorDefaultParam) {
+        // #11592
         None
-      } else if (sym.isClassConstructor && isHijackedBoxedClass(sym.owner)) {
+      } else /*if (sym.isClassConstructor && isHijackedBoxedClass(sym.owner)) {
         None
       } else*/ {
         /*def isTraitImplForwarder = dd.rhs match {

compiler/src/dotty/tools/dotc/transform/sjs/JSSymUtils.scala

@@ -158,6 +158,13 @@ object JSSymUtils {
       }
     }
 
+    /** Is this symbol a default param accessor for the constructor of a native JS class? */
+    def isJSNativeCtorDefaultParam(using Context): Boolean = {
+      sym.name.is(DefaultGetterName)
+        && sym.name.exclude(DefaultGetterName) == nme.CONSTRUCTOR
+        && sym.owner.linkedClass.hasAnnotation(jsdefn.JSNativeAnnot)
+    }
+
     def jsCallingConvention(using Context): JSCallingConvention =
       JSCallingConvention.of(sym)
 

tests/sjs-junit/test/org/scalajs/testsuite/compiler/RegressionTestScala3.scala

@@ -4,6 +4,7 @@ import org.junit.Assert.*
 import org.junit.Test
 
 import scala.scalajs.js
+import scala.scalajs.js.annotation._
 
 class RegressionTestScala3 {
   import RegressionTestScala3.*
@@ -21,6 +22,11 @@ class RegressionTestScala3 {
     assertEquals(-1, obj2.y)
     assertEquals(4, obj2.foo(5))
   }
+
+  @Test def testJSNativeDefaultCtorParamIssue11592(): Unit = {
+    assertEquals("foo", new RangeErrorIssue11592("foo").message)
+    assertEquals("", new RangeErrorIssue11592().message)
+  }
 }
 
 object RegressionTestScala3 {
@@ -33,6 +39,12 @@ object RegressionTestScala3 {
 
     def foo(x: Int): Int = new ChildClass().concreteMethod(x)
   }
+
+  @js.native
+  @JSGlobal("RangeError")
+  class RangeErrorIssue11592(msg: String = js.native) extends js.Object {
+    val message: String = js.native
+  }
 }
 
 // This class needs to be at the top-level, not in an object, to reproduce the issue