Make CharSequence.length a function instead of property

And String.length as well.

This is done for JVM interoperability: java.lang.CharSequence is an open class
and has a function 'length()' which should be implemented in subclasses
somehow.

A minor unexpected effect of this is that String.length() is now a compile-time
constant (it wasn't such as a property because properties are not supported in
compile-time constant evaluation)

 #KT-3571 Fixed

libraries/stdlib/src/kotlin/text/Strings.kt

@@ -64,6 +64,9 @@ public fun String?.orEmpty(): String = this ?: ""
 public val String.indices: IntRange
     get() = 0..length() - 1
 
+public val CharSequence.length: Int
+    get() = length()
+
 /**
  * Returns a subsequence specified by given set of indices.
  */

libraries/stdlib/src/kotlin/text/StringsJVM.kt

@@ -2,9 +2,6 @@ package kotlin
 
 import java.io.StringReader
 import java.util.ArrayList
-import java.util.HashMap
-import java.util.HashSet
-import java.util.LinkedList
 import java.util.Locale
 import java.nio.charset.Charset
 
@@ -30,8 +27,6 @@ public fun String.toUpperCase(): String = (this as java.lang.String).toUpperCase
 
 public fun String.toLowerCase(): String = (this as java.lang.String).toLowerCase()
 
-public fun String.length(): Int = (this as java.lang.String).length()
-
 public fun String.toCharArray(): CharArray = (this as java.lang.String).toCharArray()
 
 public fun String.format(vararg args: Any?): String = java.lang.String.format(this, *args)
@@ -132,10 +127,6 @@ public fun CharSequence.charAt(index: Int): Char = (this as java.lang.CharSequen
 
 public fun CharSequence.subSequence(start: Int, end: Int): CharSequence? = (this as java.lang.CharSequence).subSequence(start, end)
 
-public fun CharSequence.toString(): String? = (this as java.lang.CharSequence).toString()
-
-public fun CharSequence.length(): Int = (this as java.lang.CharSequence).length()
-
 public val CharSequence.size: Int
     get() = this.length