String.toBoolean() should be String?.toBoolean() #KT-14119

libraries/stdlib/common/src/kotlin/TextH.kt

@@ -5,6 +5,8 @@
 
 package kotlin.text
 
+import kotlin.internal.LowPriorityInOverloadResolution
+
 expect class Regex {
     constructor(pattern: String)
     constructor(pattern: String, option: RegexOption)
@@ -282,9 +284,17 @@ public expect val String.Companion.CASE_INSENSITIVE_ORDER: Comparator<String>
 
 
 /**
- * Returns `true` if the contents of this string is equal to the word "true", ignoring case, and `false` otherwise.
+ * Returns `true` if the content of this string is equal to the word "true", ignoring case, and `false` otherwise.
  */
-expect fun String.toBoolean(): Boolean
+@LowPriorityInOverloadResolution
+@kotlin.internal.InlineOnly
+public inline fun String.toBoolean(): Boolean = this.toBoolean()
+
+/**
+ * Returns `true` if this string is not `null` and its content is equal to the word "true", ignoring case, and `false` otherwise.
+ */
+@SinceKotlin("1.4")
+public expect fun String?.toBoolean(): Boolean
 
 /**
  * Parses the string as a signed [Byte] number and returns the result.

libraries/stdlib/jdk7/test/UseAutoCloseableResourceTest.kt

@@ -5,14 +5,12 @@
 
 package kotlin.jdk7.test
 
+import test.platformNull
 import java.io.*
-import java.util.*
 import kotlin.test.*
 
 class UseAutoCloseableResourceTest {
 
-    @Suppress("HasPlatformType", "UNCHECKED_CAST") fun <T> platformNull() = Collections.singletonList(null as T).first()
-
     class Resource(val faultyClose: Boolean = false) : AutoCloseable {
 
         var isClosed = false

libraries/stdlib/jdk7/test/UseCloseableResourceTest.kt

@@ -5,14 +5,12 @@
 
 package kotlin.jdk7.test
 
+import test.platformNull
 import java.io.*
-import java.util.*
 import kotlin.test.*
 
 class UseCloseableResourceTest {
 
-    @Suppress("HasPlatformType", "UNCHECKED_CAST") fun <T> platformNull() = Collections.singletonList(null as T).first()
-
     class Resource(val faultyClose: Boolean = false) : Closeable {
 
         var isClosed = false

libraries/stdlib/js/src/kotlin/text/numberConversions.kt

@@ -7,9 +7,10 @@ package kotlin.text
 
 
 /**
- * Returns `true` if the contents of this string is equal to the word "true", ignoring case, and `false` otherwise.
+ * Returns `true` if this string is not `null` and its content is equal to the word "true", ignoring case, and `false` otherwise.
  */
-public actual fun String.toBoolean(): Boolean = toLowerCase() == "true"
+@SinceKotlin("1.4")
+public actual fun String?.toBoolean(): Boolean = this != null && this.toLowerCase() == "true"
 
 /**
  * Parses the string as a signed [Byte] number and returns the result.

libraries/stdlib/jvm/src/kotlin/text/StringNumberConversionsJVM.kt

@@ -46,10 +46,12 @@ public actual inline fun Int.toString(radix: Int): String = java.lang.Integer.to
 public actual inline fun Long.toString(radix: Int): String = java.lang.Long.toString(this, checkRadix(radix))
 
 /**
- * Returns `true` if the contents of this string is equal to the word "true", ignoring case, and `false` otherwise.
+ * Returns `true` if this string is not `null` and its content is equal to the word "true", ignoring case, and `false` otherwise.
  */
+@JvmName("toBooleanNullable")
+@SinceKotlin("1.4")
 @kotlin.internal.InlineOnly
-public actual inline fun String.toBoolean(): Boolean = java.lang.Boolean.parseBoolean(this)
+public actual inline fun String?.toBoolean(): Boolean = java.lang.Boolean.parseBoolean(this)
 
 /**
  * Parses the string as a signed [Byte] number and returns the result.

libraries/stdlib/jvm/test/io/UseCloseableResourceTest.kt

@@ -5,8 +5,8 @@
 
 package test.io
 
+import test.platformNull
 import java.io.*
-import java.util.*
 import kotlin.test.*
 
 class UseCloseableResourceTest {
@@ -23,9 +23,6 @@ class UseCloseableResourceTest {
         assertEquals("World", secondLine)
     }
 
-
-    @Suppress("HasPlatformType", "UNCHECKED_CAST") fun <T> platformNull() = Collections.singletonList(null as T).first()
-
     class Resource(val faultyClose: Boolean = false) : Closeable {
 
         var isClosed = false

libraries/stdlib/jvm/test/text/StringJVMTest.kt

@@ -104,4 +104,19 @@ class StringJVMTest {
         assertEquals("dzdzdz", "DZdzdz".decapitalize(Locale.US))
         assertEquals("dzdzdz", "Dzdzdz".decapitalize(Locale.US))
     }
+
+    @Test
+    fun stringToBoolean() {
+        assertFalse(platformNull<String>().toBoolean())
+    }
+
+    @Test
+    fun stringEquals() {
+        assertFalse(platformNull<String>().equals("sample", ignoreCase = false))
+        assertFalse(platformNull<String>().equals("sample", ignoreCase = true))
+        assertFalse("sample".equals(platformNull<String>(), ignoreCase = false))
+        assertFalse("sample".equals(platformNull(), ignoreCase = true))
+        assertTrue(platformNull<String>().equals(platformNull(), ignoreCase = true))
+        assertTrue(platformNull<String>().equals(platformNull<String>(), ignoreCase = false))
+    }
 }

libraries/stdlib/test/text/StringNumberConversionTest.kt

@@ -15,6 +15,7 @@ class StringNumberConversionTest {
         assertEquals(true, "True".toBoolean())
         assertEquals(false, "false".toBoolean())
         assertEquals(false, "not so true".toBoolean())
+        assertEquals(false, (null as String?).toBoolean())
     }
 
     @Test fun toByte() {