A couple utility methods

PsiCodegenPredictor.getFileForCodegenNamedClass() returns JetFile which
contains a declaration which will produce a class with a given name.
PsiCodegenPredictor.getFileForNamespacePartName() returns JetFile which
produces a namespace part with the given name.

BindingContextUtils.getContainingFile() returns JetFile which contains a
declaration which is matched to a given descriptor.

DescriptorUtils.findTopLevelParent() finds a top-level (i.e. its containing
declaration is NamespaceDescriptor) parent for a descriptor.

Also DescriptorUtils.isTopLevelFunction() is changed a little to accept not
only a function, but any descriptor

compiler/frontend/src/org/jetbrains/jet/lang/resolve/BindingContextUtils.java

@@ -112,6 +112,19 @@ public class BindingContextUtils {
         return null;
     }
 
+    @Nullable
+    public static JetFile getContainingFile(@NotNull BindingContext context, @NotNull DeclarationDescriptor declarationDescriptor) {
+        // declarationDescriptor may describe a synthesized element which doesn't have PSI
+        // To workaround that, we find a top-level parent (which is inside a NamespaceDescriptor), which is guaranteed to have PSI
+        DeclarationDescriptor descriptor = DescriptorUtils.findTopLevelParent(declarationDescriptor);
+        if (descriptor == null) return null;
+
+        PsiElement declaration = descriptorToDeclaration(context, descriptor);
+        if (declaration == null) return null;
+
+        return (JetFile) declaration.getContainingFile();
+    }
+
     // TODO these helper methods are added as a workaround to some compiler bugs in Kotlin...
 
     // NOTE this is used by KDoc

compiler/frontend/src/org/jetbrains/jet/lang/resolve/DescriptorUtils.java

@@ -129,8 +129,17 @@ public class DescriptorUtils {
         return getFQName(containingDeclaration).child(descriptor.getName());
     }
 
-    public static boolean isTopLevelFunction(@NotNull SimpleFunctionDescriptor functionDescriptor) {
-        return functionDescriptor.getContainingDeclaration() instanceof NamespaceDescriptor;
+    public static boolean isTopLevelDeclaration(@NotNull DeclarationDescriptor descriptor) {
+        return descriptor.getContainingDeclaration() instanceof NamespaceDescriptor;
+    }
+
+    @Nullable
+    public static DeclarationDescriptor findTopLevelParent(@NotNull DeclarationDescriptor declarationDescriptor) {
+        DeclarationDescriptor descriptor = declarationDescriptor;
+        while (!(descriptor == null || isTopLevelDeclaration(descriptor))) {
+            descriptor = descriptor.getContainingDeclaration();
+        }
+        return descriptor;
     }
 
     @Nullable