fix error reporting in CodegenTestCase

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

@@ -8,6 +8,7 @@ import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Pair;
 import com.intellij.psi.PsiElement;
 import com.intellij.util.containers.Stack;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.codegen.intrinsics.IntrinsicMethods;
 import org.jetbrains.jet.lang.cfg.pseudocode.JetControlFlowDataTraceFactory;
 import org.jetbrains.jet.lang.descriptors.ClassDescriptor;
@@ -23,6 +24,7 @@ import java.util.Collections;
 import java.util.List;
 
 public class GenerationState {
+    @NotNull
     private final ClassFileFactory factory;
     private final Project project;
 
@@ -38,6 +40,7 @@ public class GenerationState {
         this.intrinsics = new IntrinsicMethods(project, standardLibrary);
     }
 
+    @NotNull
     public ClassFileFactory getFactory() {
         return factory;
     }

compiler/backend/src/org/jetbrains/jet/compiler/CompileSession.java

@@ -4,6 +4,7 @@ import com.google.common.base.Predicates;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.PsiManager;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.JetCoreEnvironment;
 import org.jetbrains.jet.codegen.ClassBuilderFactory;
 import org.jetbrains.jet.codegen.ClassFileFactory;
@@ -107,6 +108,7 @@ public class CompileSession {
         return !errorCollector.hasErrors;
     }
 
+    @NotNull
     public ClassFileFactory generate() {
         GenerationState generationState = new GenerationState(myEnvironment.getProject(), ClassBuilderFactory.BINARIES);
         generationState.compileCorrectFiles(myBindingContext, mySourceFiles);