Transform CharSequence.length to property

compiler/testData/codegen/boxWithJava/collections/charSequence/J.java

@@ -3,6 +3,7 @@ import java.util.*;
 public class J {
 
     public static class B extends A {
+        public int getLength() { return 456; }
         public char get(int index) {
             if (index == 1) return 'a';
             return super.get(index);
@@ -13,6 +14,10 @@ public class J {
         B b = new B();
         CharSequence cs = (CharSequence) b;
 
+        if (cs.length() != 456) return "fail 01";
+        if (b.length() != 456) return "fail 02";
+        if (b.getLength() != 456) return "fail 03";
+
         if (cs.charAt(0) != 'z') return "fail 1";
         if (b.get(0) != 'z') return "fail 2";
 

compiler/testData/codegen/boxWithJava/collections/charSequence/charSequence.kt

@@ -1,7 +1,5 @@
 open class A : CharSequence {
-    override fun length(): Int {
-        throw UnsupportedOperationException()
-    }
+    override val length: Int = 123
 
     override fun get(index: Int) = 'z';
 
@@ -24,5 +22,13 @@ fun box(): String {
     if (b.get(1) != 'a') return "fail 12"
     if (a.get(1) != 'z') return "fail 13"
 
+    var cs: CharSequence = a
+    if (a.length != 123) return "fail 14"
+    if (cs.length != 123) return "fail 15"
+
+    cs = b
+    if (b.length != 456) return "fail 16"
+    if (b.length != 456) return "fail 17"
+
     return J.foo();
 }