Add String.contains with Char argument. Fixes #KT-7239.

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

@@ -694,6 +694,15 @@ public fun String.contains(seq: CharSequence, ignoreCase: Boolean = false): Bool
         indexOf(seq.toString(), ignoreCase = ignoreCase) >= 0
 
 
+/**
+ * Returns `true` if this string contains the specified character.
+ *
+ * @param ignoreCase `true` to ignore character case when comparing characters. By default `false`.
+ */
+public fun String.contains(char: Char, ignoreCase: Boolean = false): Boolean =
+        indexOf(char, ignoreCase = ignoreCase) >= 0
+
+
 // rangesDelimitedBy
 
 

libraries/stdlib/test/text/StringTest.kt

@@ -478,12 +478,16 @@ class StringTest {
 
 
     test fun contains() {
-        assertTrue("sample".contains("pl"))
-        assertFalse("sample".contains("PL"))
+        assertTrue("pl" in "sample")
+        assertFalse("PL" in "sample")
         assertTrue("sömple".contains("Ö", ignoreCase = true))
 
-        assertTrue("sample".contains(""))
-        assertTrue("".contains(""))
+        assertTrue("" in "sample")
+        assertTrue("" in "")
+
+        assertTrue('ö' in "sömple")
+        assertFalse('Ö' in "sömple")
+        assertTrue("sömple".contains('Ö', ignoreCase = true))
     }
 
     test fun equalsIgnoreCase() {