Fix ClassCastException with nullable chars

#KT-4210 Fixed
 #KT-4098 Fixed
 #KT-4251 Fixed

compiler/backend/src/org/jetbrains/jet/codegen/StackValue.java

@@ -251,13 +251,19 @@ public abstract class StackValue {
             }
         }
         else if (fromType.getSort() == Type.OBJECT) {
-            if (toType.getSort() == Type.BOOLEAN || toType.getSort() == Type.CHAR) {
-                coerce(fromType, boxType(toType), v);
+            if (fromType.equals(getType(Boolean.class)) || fromType.equals(getType(Character.class))) {
+                unbox(unboxType(fromType), v);
+                coerce(unboxType(fromType), toType, v);
             }
             else {
-                coerce(fromType, getType(Number.class), v);
+                if (toType.getSort() == Type.BOOLEAN || toType.getSort() == Type.CHAR) {
+                    coerce(fromType, boxType(toType), v);
+                }
+                else {
+                    coerce(fromType, getType(Number.class), v);
+                }
+                unbox(toType, v);
             }
-            unbox(toType, v);
         }
         else {
             v.cast(fromType, toType);

compiler/testData/codegen/box/primitiveTypes/kt4098.kt

@@ -0,0 +1,10 @@
+fun box(): String {
+    val c = '0': Char?
+    c!!.toInt()
+
+    "123456"?.get(0)!!.toInt()
+
+    "123456"!!.get(0).toInt()
+
+    return "OK"
+}

compiler/testData/codegen/box/primitiveTypes/kt4210.kt

@@ -0,0 +1,16 @@
+fun box(): String {
+    val s: String? = "abc"
+    val c = s?.get(0)!! - 'b'
+    if (c != -1) return "Fail c: $c"
+
+    val d = 'b' - s?.get(2)!!
+    if (d != -1) return "Fail d: $d"
+
+    val e = s?.get(2)!! - s?.get(0)!!
+    if (e != 2) return "Fail e: $e"
+
+    val f = s?.get(2)!!.minus(s?.get(0)!!)
+    if (f != 2) return "Fail f: $f"
+
+    return "OK"
+}

compiler/testData/codegen/box/primitiveTypes/kt4251.kt

@@ -0,0 +1,5 @@
+fun box(): String {
+    val a: Char? = 'a'
+    val result = a!! < 'b'
+    return if (result) "OK" else "Fail"
+}

compiler/testData/codegen/box/primitiveTypes/nullableCharBoolean.kt

@@ -0,0 +1,9 @@
+fun box(): String {
+    val c: Char? = 'a'
+    if (c!! - 'a' != 0) return "Fail c"
+
+    val b: Boolean? = false
+    if (b!!) return "Fail b"
+
+    return "OK"
+}

compiler/tests/org/jetbrains/jet/codegen/generated/BlackBoxCodegenTestGenerated.java

@@ -3807,6 +3807,21 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest("compiler/testData/codegen/box/primitiveTypes/kt3576.kt");
         }
         
+        @TestMetadata("kt4098.kt")
+        public void testKt4098() throws Exception {
+            doTest("compiler/testData/codegen/box/primitiveTypes/kt4098.kt");
+        }
+        
+        @TestMetadata("kt4210.kt")
+        public void testKt4210() throws Exception {
+            doTest("compiler/testData/codegen/box/primitiveTypes/kt4210.kt");
+        }
+        
+        @TestMetadata("kt4251.kt")
+        public void testKt4251() throws Exception {
+            doTest("compiler/testData/codegen/box/primitiveTypes/kt4251.kt");
+        }
+        
         @TestMetadata("kt446.kt")
         public void testKt446() throws Exception {
             doTest("compiler/testData/codegen/box/primitiveTypes/kt446.kt");
@@ -3892,6 +3907,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest("compiler/testData/codegen/box/primitiveTypes/nullAsNullableIntIsNull.kt");
         }
         
+        @TestMetadata("nullableCharBoolean.kt")
+        public void testNullableCharBoolean() throws Exception {
+            doTest("compiler/testData/codegen/box/primitiveTypes/nullableCharBoolean.kt");
+        }
+        
         @TestMetadata("unboxComparable.kt")
         public void testUnboxComparable() throws Exception {
             doTest("compiler/testData/codegen/box/primitiveTypes/unboxComparable.kt");