KT-2457 Verify error when comparing not null value with null in when

backend-side changes

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

@@ -2848,7 +2848,7 @@ The "returned" value of try expression with no finally is either the last expres
         }
         else if (pattern instanceof JetExpressionPattern) {
             if (expressionToMatch != null) {
-                final Type subjectType = expressionToMatch.type;
+                Type subjectType = expressionToMatch.type;
                 expressionToMatch.dupReceiver(v);
                 expressionToMatch.put(subjectType, v);
                 JetExpression condExpression = ((JetExpressionPattern) pattern).getExpression();
@@ -2857,6 +2857,10 @@ The "returned" value of try expression with no finally is either the last expres
                 Type condType;
                 if (isNumberPrimitive(subjectType) || subjectType.getSort() == Type.BOOLEAN) {
                     condType = asmType(condJetType);
+                    if (!(isNumberPrimitive(condType) || condType.getSort() == Type.BOOLEAN)) {
+                        subjectType = JetTypeMapper.boxType(subjectType);
+                        expressionToMatch.coerce(subjectType, v);
+                    }
                 }
                 else {
                     condType = TYPE_OBJECT;

compiler/testData/codegen/patternMatching/matchNotNullAgainstNullable.kt

@@ -0,0 +1,7 @@
+fun foo(i: Int, j: Int?): String =
+    when (i) {
+        j -> "OK"
+        else -> "Fail"
+    }
+
+fun box(): String = foo(0, 0)

compiler/testData/codegen/regressions/kt2457.kt

@@ -0,0 +1,8 @@
+fun foo(i: Int) : Int =
+    when (i) {
+        1 -> 1
+        null -> 1
+        else -> 1
+    }
+
+fun box() : String = if (foo(1) == 1) "OK" else "fail"

compiler/tests/org/jetbrains/jet/codegen/PatternMatchingTest.java

@@ -162,4 +162,12 @@ public class PatternMatchingTest extends CodegenTestCase {
     public void testKt2466() throws Exception {
         blackBoxFile("patternMatching/kt2466.kt");
     }
+
+    public void testMatchNotNullAgainstNullable() throws Exception {
+        blackBoxFile("patternMatching/matchNotNullAgainstNullable.kt");
+    }
+
+    public void testKt2457() throws Exception {
+        blackBoxFile("regressions/kt2457.kt");
+    }
 }