remove attempt to optimize using 'if' statement as the last one in a loop which created far more problems that it fixed

#KT-1978 Fixed

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

@@ -264,10 +264,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
         Label elseLabel = new Label();
         condition.condJump(elseLabel, true, v);   // == 0, i.e. false
 
-        Label end = continueLabel == null ? new Label() : continueLabel;
-        
-        if (continueLabel != null)
-            asmType = Type.VOID_TYPE;
+        Label end = new Label();
 
         gen(thenExpression, asmType);
 
@@ -276,10 +273,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
 
         gen(elseExpression, asmType);
 
-        if (end != continueLabel)
-            v.mark(end);
-        else
-            v.goTo(end);
+        v.mark(end);
 
         return StackValue.onStack(asmType);
     }

compiler/testData/codegen/regressions/kt1978.kt

@@ -0,0 +1,10 @@
+fun aa(vararg a : String): String = a[0]
+
+fun box(): String {
+    var result: String = ""
+    var i = 1
+    while (3 > i++) {
+        result = aa(if (true) "OK" else "fail")
+    }
+    return result
+}

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

@@ -126,4 +126,9 @@ public class VarArgTest extends CodegenTestCase {
         assertEquals("mama", Array.get(invoke, 0));
         assertEquals("papa", Array.get(invoke, 1));
     }
+
+    public void testKt1978() {
+        createEnvironmentWithMockJdkAndIdeaAnnotations(CompilerSpecialMode.JDK_HEADERS);
+        blackBoxFile("regressions/kt1978.kt");
+    }
 }