JVM_IR never generate setter synthetic accessor for 'val' field

KT-49316

compiler/testData/codegen/box/syntheticAccessors/kt49316.kt

@@ -0,0 +1,27 @@
+// IGNORE_BACKEND: JS
+//  java.lang.AssertionError
+//    at org.jetbrains.kotlin.js.translate.context.TranslationContext.getDispatchReceiver(TranslationContext.java:590)
+//    at org.jetbrains.kotlin.js.translate.utils.TranslationUtils.backingFieldReference(TranslationUtils.java:237)
+//    at org.jetbrains.kotlin.js.translate.utils.TranslationUtils.assignmentToBackingField(TranslationUtils.java:250)
+//    at org.jetbrains.kotlin.js.translate.reference.BackingFieldAccessTranslator.translateAsSet(BackingFieldAccessTranslator.java:60)
+//    ...
+
+// FILE: kt49316.kt
+import a.*
+
+// This test should become irrelevant after KT-35565 is fixed.
+
+fun test(foo: Foo): String {
+    return foo.s
+
+    // VAL_REASSIGNMENT not reported in unreachable code.
+    // Make sure there's no BE internal error here.
+    foo.s = "oops"
+}
+
+fun box() = test(Foo("OK"))
+
+// FILE: Foo.kt
+package a
+
+class Foo(val s: String)