export function getModuleInstanceState(node: Node): ModuleInstanceState {
    // A module is uninstantiated if it contains only
    // 1. interface declarations, type alias declarations
    if (node.kind === SyntaxKind.InterfaceDeclaration || node.kind === SyntaxKind.TypeAliasDeclaration) {
        return ModuleInstanceState.NonInstantiated;
    }
    // 2. const enum declarations
    else if (isConstEnumDeclaration(node)) {
        return ModuleInstanceState.ConstEnumOnly;
    }
    // 3. non-exported import declarations
    else if ((node.kind === SyntaxKind.ImportDeclaration || node.kind === SyntaxKind.ImportEqualsDeclaration) && !(node.flags & NodeFlags.Export)) {
        return ModuleInstanceState.NonInstantiated;
    }
    // 4. other uninstantiated module declarations.
    else if (node.kind === SyntaxKind.ModuleBlock) {
        let state = ModuleInstanceState.NonInstantiated;
        forEachChild(node, n => {
            switch (getModuleInstanceState(n)) {
                case ModuleInstanceState.NonInstantiated:
                    // child is non-instantiated - continue searching
                    return false;
                case ModuleInstanceState.ConstEnumOnly:
                    // child is const enum only - record state and continue searching
                    state = ModuleInstanceState.ConstEnumOnly;
                    return false;
                case ModuleInstanceState.Instantiated:
                    // child is instantiated - record state and stop
                    state = ModuleInstanceState.Instantiated;
                    return true;
            }
        });
        return state;
    }
    else if (node.kind === SyntaxKind.ModuleDeclaration) {
        return getModuleInstanceState((<ModuleDeclaration>node).body);
    }
    else {
        return ModuleInstanceState.Instantiated;
    }
}