Use Char.MIN_VALUE and MAX_VALUE in tests

compiler/testData/codegen/box/binaryOp/overflowChar.kt

@@ -1,10 +1,11 @@
 fun box(): String {
-    val c1: Char = 0.toChar()
+    val c1: Char = Char.MIN_VALUE
     val c2 = c1 - 1
-    if (c2 < c1) return "fail: 0.toChar() - 1 should overflow to positive."
+    if (c2 < c1) return "fail: Char.MIN_VALUE - 1 should overflow to positive."
 
-    val c3 = c2 + 1
-    if (c3 > c2) return "fail: FFFF.toChar() + 1 should overflow to zero."
+    val c3: Char = Char.MAX_VALUE
+    val c4 = c3 + 1
+    if (c4 > c3) return "fail: Char.MAX_VALUE + 1 should overflow to zero."
 
     return "OK"
 }

compiler/testData/codegen/box/ranges/forWithPossibleOverflow/forInDownToCharMinValue.kt

@@ -1,6 +1,6 @@
 // WITH_RUNTIME
 
-const val M = 0.toChar()
+const val M = Char.MIN_VALUE
 
 fun box(): String {
     var count = 0

compiler/testData/codegen/box/ranges/forWithPossibleOverflow/forInDownToCharMinValueReversed.kt

@@ -1,7 +1,7 @@
 // IGNORE_BACKEND: JS_IR
 // WITH_RUNTIME
 
-const val M = 0.toChar()
+const val M = Char.MIN_VALUE
 
 fun box(): String {
     var count = 0

compiler/testData/codegen/box/ranges/forWithPossibleOverflow/forInRangeToCharMaxValue.kt

@@ -1,5 +1,5 @@
 // IGNORE_BACKEND: JS_IR
-const val M = 0xFFFF.toChar()
+const val M = Char.MAX_VALUE
 
 fun box(): String {
     var count = 0

compiler/testData/codegen/box/ranges/forWithPossibleOverflow/forInRangeToCharMaxValueReversed.kt

@@ -1,7 +1,7 @@
 // IGNORE_BACKEND: JS_IR
 // WITH_RUNTIME
 
-const val M = 0xFFFF.toChar()
+const val M = Char.MAX_VALUE
 
 fun box(): String {
     var count = 0

libraries/stdlib/jvm/test/numbers/BuiltinCompanionJVMTest.kt

@@ -55,6 +55,8 @@ class BuiltinCompanionJVMTest {
 
     @Test fun charTest() {
         val ch = Char
+        assertEquals(java.lang.Character.MIN_VALUE, ch.MIN_VALUE)
+        assertEquals(java.lang.Character.MAX_VALUE, ch.MAX_VALUE)
         assertEquals(java.lang.Character.MIN_SURROGATE, ch.MIN_SURROGATE)
         assertEquals(java.lang.Character.MAX_SURROGATE, ch.MAX_SURROGATE)
         assertEquals(java.lang.Character.MIN_LOW_SURROGATE, ch.MIN_LOW_SURROGATE)

libraries/stdlib/test/numbers/NumbersTest.kt

@@ -94,6 +94,15 @@ class NumbersTest {
         expect(Float.NEGATIVE_INFINITY) { -Float.MAX_VALUE * 2 }
         expect(0.0F) { Float.MIN_VALUE / 2.0F }
     }
+
+    @Test fun charMinMaxValues() {
+        assertTrue(Char.MIN_VALUE.toInt() == 0)
+        assertTrue(Char.MAX_VALUE.toInt() > 0)
+
+        // overflow behavior
+        expect(Char.MIN_VALUE) { Char.MAX_VALUE + one }
+        expect(Char.MAX_VALUE) { Char.MIN_VALUE - one }
+    }
     
     @Test fun doubleProperties() {
         for (value in listOf(1.0, 0.0, Double.MIN_VALUE, Double.MAX_VALUE))

libraries/stdlib/test/ranges/RangeTest.kt

@@ -172,7 +172,7 @@ public class RangeTest {
         assertTrue('Y' in openRange)
         assertFalse('Z' in openRange)
 
-        assertTrue(('A' until '\u0000').isEmpty())
+        assertTrue(('A' until Char.MIN_VALUE).isEmpty())
     }
 
     @Test fun doubleRange() {