fixes bugs in TypeInfo

idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -1740,7 +1740,22 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                 v.dup();
             }
             Type type = typeMapper.boxType(typeMapper.mapType(jetType, OwnerKind.INTERFACE));
-            v.instanceOf(type);
+            if(jetType.isNullable()) {
+                Label nope = new Label();
+                Label end = new Label();
+
+                v.dup();
+                v.ifnull(nope);
+                v.instanceOf(type);
+                v.goTo(end);
+                v.mark(nope);
+                v.pop();
+                v.aconst(1);
+                v.mark(end);
+            }
+            else {
+                v.instanceOf(type);
+            }
         }
     }
 

idea/src/org/jetbrains/jet/lang/types/JetTypeInferrer.java

@@ -11,6 +11,7 @@ import com.intellij.psi.tree.TokenSet;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.JetNodeTypes;
+import org.jetbrains.jet.lang.ErrorHandler;
 import org.jetbrains.jet.lang.JetSemanticServices;
 import org.jetbrains.jet.lang.cfg.JetFlowInformationProvider;
 import org.jetbrains.jet.lang.descriptors.*;
@@ -1708,7 +1709,7 @@ public class JetTypeInferrer {
                         return;
                     }
                     if (TypeUtils.intersect(semanticServices.getTypeChecker(), Sets.newHashSet(type, subjectType)) == null) {
-                        context.trace.getErrorHandler().genericError(reportErrorOn.getNode(), "Incompatible types: " + type + " and " + subjectType); // TODO : message
+                        context.trace.getErrorHandler().genericError(reportErrorOn.getNode(), "Incompatible types: " + type + " and " + subjectType + " " + ErrorHandler.atLocation(reportErrorOn));
                     }
                 }
 

idea/testData/codegen/regressions/kt259.jet

@@ -1,20 +1,66 @@
 class A() {}
-class B<T>() {}
+class B<T>() {
+    fun isT (a : Any?) : Boolean {
+        return a is T
+    }
+}
 
-fun box() : String {
+fun t1() : Boolean {
     val a = A()
-    System.out?.println(a is A)   //true
-    System.out?.println(a is A?)  //true
+    if(a !is A)   return false
+    if(a !is A?)   return false
+    if(null !is A?)   return false
+    return true
+}
 
+fun t2 () : Boolean {
     val b = B<String>()
-    System.out?.println(b is B<String>)   //true
-    System.out?.println(b is B<String>?)  //false !!!
+    if(b !is B<String>)   return false
+    if(b !is B<String>?)  return false
+    if(null !is B<String>?)  return false
 
     val v = b as B<String>   //ok
     val u = b as B<String>?  //TypeCastException
 
     val w : B<String>? = b as B<String>   //ok
     val x = w as B<String>?  //TypeCastException
+    return true
+}
 
+fun t3 () : Boolean {
+    val b = B<String>()
+    if(!b.isT("aaa")) return false
+
+    if(b.isT(10))     return false
+    if(b.isT(null))   return false
+
+    val d = B<String?>()
+    if(!d.isT("aaa")) return false
+    if(d.isT(10))     return false
+    if(!d.isT(null))  return false
+
+    val c = B<Int>()
+    if(c.isT("aaa")) return false
+    if(!c.isT(10))   return false
+    if(c.isT(null)) return false
+
+    val e = B<Int?>()
+    if(e.isT("aaa")) return false
+    if(!e.isT(10))   return false
+    if(!e.isT(null)) return false
+
+    return true
+}
+
+fun box() : String {
+    if(!t1()) {
+        return "t1 failed"
+    }
+    if(!t2()) {
+        return "t2 failed"
+    }
+    if(!t3()) {
+        return "t3 failed"
+    }
     return "OK"
 }