Return Unit.VALUE if Unit or Any is expected

StackValue.coerce will do its job in casting void to Unit correctly

 #KT-4212 Fixed

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

@@ -1607,13 +1607,10 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
     public void returnExpression(JetExpression expr) {
         StackValue lastValue = gen(expr);
 
-        if (lastValue.type != Type.VOID_TYPE) {
+        if (!endsWithReturn(expr)) {
             lastValue.put(returnType, v);
             v.areturn(returnType);
         }
-        else if (!endsWithReturn(expr)) {
-            v.areturn(returnType);
-        }
     }
 
     private static boolean endsWithReturn(JetElement bodyExpression) {

compiler/testData/codegen/box/unit/kt4212.kt

@@ -0,0 +1,20 @@
+fun foo(): Any? = bar()
+
+fun bar() {}
+
+fun baz(): Any? {
+    return bar()
+}
+
+fun quux(): Unit? = bar()
+
+fun box(): String {
+    foo()
+
+    if (foo() != Unit.VALUE) return "Fail 1"
+    if (foo() != bar()) return "Fail 2"
+    if (bar() != baz()) return "Fail 3"
+    if (baz() != quux()) return "Fail 4"
+
+    return "OK"
+}

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

@@ -4764,6 +4764,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), "org.jetbrains.jet.generators.tests.GenerateTests", new File("compiler/testData/codegen/box/unit"), Pattern.compile("^(.+)\\.kt$"), true);
         }
         
+        @TestMetadata("kt4212.kt")
+        public void testKt4212() throws Exception {
+            doTest("compiler/testData/codegen/box/unit/kt4212.kt");
+        }
+        
         @TestMetadata("kt4265.kt")
         public void testKt4265() throws Exception {
             doTest("compiler/testData/codegen/box/unit/kt4265.kt");