support putting the result of a dummy comparison to stack (KT-1899)

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

@@ -2922,7 +2922,7 @@ If finally block is present, its last expression is the value of try expression.
         }
         if(entries.size() == 0) {
             v.visitFieldInsn(Opcodes.GETSTATIC, "jet/Tuple0", "INSTANCE", "Ljet/Tuple0;");
-            return StackValue.onStack(Type.getObjectType("jet/Tuple0"));
+            return StackValue.onStack(TUPLE0_TYPE);
         }
 
         final String className = "jet/Tuple" + entries.size();

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

@@ -61,6 +61,7 @@ public class JetTypeMapper {
     public static final Type JL_CLASS_TYPE = Type.getObjectType("java/lang/Class");
 
     public static final Type ARRAY_GENERIC_TYPE = Type.getType(Object[].class);
+    public static final Type TUPLE0_TYPE = Type.getObjectType("jet/Tuple0");
 
     private JetStandardLibrary standardLibrary;
     public BindingContext bindingContext;

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

@@ -203,8 +203,9 @@ public abstract class StackValue {
                 v.pop2();
         }
         else if (type.getSort() != Type.VOID && this.type.getSort() == Type.VOID) {
-            if(type.getSort() == Type.OBJECT)
-                v.visitFieldInsn(Opcodes.GETSTATIC, "jet/Tuple0", "INSTANCE", "Ljet/Tuple0;");
+            if(type.getSort() == Type.OBJECT) {
+                putTuple0Instance(v);
+            }
             else if(type == Type.LONG_TYPE)
                 v.lconst(0);
             else if(type == Type.FLOAT_TYPE)
@@ -243,6 +244,10 @@ public abstract class StackValue {
         }
     }
 
+    protected static void putTuple0Instance(InstructionAdapter v) {
+        v.visitFieldInsn(Opcodes.GETSTATIC, "jet/Tuple0", "INSTANCE", "Ljet/Tuple0;");
+    }
+
     protected void putAsBoolean(InstructionAdapter v) {
         Label ifTrue = new Label();
         Label end = new Label();
@@ -393,6 +398,10 @@ public abstract class StackValue {
             if (type == Type.VOID_TYPE) {
                 return;
             }
+            if (type.equals(JetTypeMapper.TUPLE0_TYPE)) {
+                putTuple0Instance(v);
+                return;
+            }
             if (type != Type.BOOLEAN_TYPE) {
                 throw new UnsupportedOperationException("don't know how to put a compare as a non-boolean type " + type);
             }

compiler/testData/codegen/regressions/kt1899.kt

@@ -0,0 +1,5 @@
+fun box(): String {
+  if (1 != 0) {
+  }
+  return "OK"
+}

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

@@ -336,4 +336,9 @@ public class ControlStructuresTest extends CodegenTestCase {
         createEnvironmentWithMockJdkAndIdeaAnnotations(CompilerSpecialMode.JDK_HEADERS);
         blackBoxFile("regressions/kt2147.kt");
     }
+
+    public void testIfDummy() throws Exception {
+        createEnvironmentWithMockJdkAndIdeaAnnotations(CompilerSpecialMode.JDK_HEADERS);
+        blackBoxFile("regressions/kt1899.kt");
+    }
 }