Build.cs not working even after being restores to it's previous version

Question

I'm trying to compile a project I'm working on and this error mesages pops out:

Invalidating makefile for SpaceShooterEditor (SpaceShooter.Build.cs modified)
While compiling E:\ue projects\SpaceShooter\Intermediate\Build\BuildRules\SpaceShooterModuleRules.dll:
e:\ue projects\SpaceShooter\Source\SpaceShooter\SpaceShooter.Build.cs(3,29) : error CS0246: The type or namespace name 'ModuleRules' could not be found (are you missing a using directive or an assembly reference?)
e:\ue projects\SpaceShooter\Source\SpaceShooter\SpaceShooter.Build.cs(5,25) : error CS0246: The type or namespace name 'ReadOnlyTargetRules' could not be found (are you missing a using directive or an assembly reference?)
ERROR: Unable to compile source files.

Any idea why this might happen? Last night i was trying to code a widget, modified the build.cs, then replaced the modified version (which chrashed the game) with a build.cs that worked previously, and still nothing? Is there any hope to make it work or should i start over? Moreover, how can this be avoided?

I already did the restarts and refreshes. I went to even delete the binaries and some cashed files and it didn't work.

Below you'll find the content of the Build.cs:

public class SpaceShooter : ModuleRules
{
    public SpaceShooter(ReadOnlyTargetRules Target) : base(Target)
    {
        PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;

        PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore" });

        PrivateDependencyModuleNames.AddRange(new string[] { });

        // Uncomment if you are using Slate UI
        // PrivateDependencyModuleNames.AddRange(new string[] { "Slate", "SlateCore" });

        // Uncomment if you are using online features
        // PrivateDependencyModuleNames.Add("OnlineSubsystem");

        // To include OnlineSubsystemSteam, add it to the plugins section in your uproject file with the Enabled attribute set to true
    }
}

When i try to input specify the using UnrealBuildTool;, Visual Studio, for some reason, deletes it when i hit compile or save.

Answer 1

After some digging, i found out that wrapping the content in a namespace UnrealBuidTool.Rules{} solves this. In the end, the build file looks like this:

namespace UnrealBuildTool.Rules
{
    public class SpaceShooter : ModuleRules
    {
        public SpaceShooter(ReadOnlyTargetRules Target) : base(Target)
        {
            PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;

            PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore" });

            PrivateDependencyModuleNames.AddRange(new string[] { });

            // Uncomment if you are using Slate UI
            // PrivateDependencyModuleNames.AddRange(new string[] { "Slate", "SlateCore" });

            // Uncomment if you are using online features
            // PrivateDependencyModuleNames.Add("OnlineSubsystem");

            // To include OnlineSubsystemSteam, add it to the plugins section in your uproject file with the Enabled attribute set to true
        }
    }
}