MPS Error when building plugin for IDEA: Language.java:5: error: package jetbrains.mps.smodel.language does not exist

When building an IDEA plugin via the built-in ant template, I get this error and a few more.

I don't know where the Language.java came from, as I did not manually create any Java files, but I know where it is on the project. I have attached a screenshot of the error below and the problematic Language.java file as well.

The root directory of the project is C:\Users\micha\source\robotassembly\language

// Language.java
package robotassembly;

/*Generated by MPS */

import jetbrains.mps.smodel.language.LanguageRuntime;
import jetbrains.mps.smodel.adapter.ids.SLanguageId;
import java.util.Collection;
import org.jetbrains.mps.openapi.language.SLanguage;
import jetbrains.mps.smodel.adapter.structure.MetaAdapterFactory;
import jetbrains.mps.smodel.runtime.ILanguageAspect;
import jetbrains.mps.openapi.editor.descriptor.EditorAspectDescriptor;
import robotassembly.editor.EditorAspectDescriptorImpl;
import jetbrains.mps.smodel.runtime.StructureAspectDescriptor;
import jetbrains.mps.smodel.runtime.ConceptPresentationAspect;
import robotassembly.structure.ConceptPresentationAspectImpl;
import jetbrains.mps.text.rt.TextGenAspectDescriptor;
import org.jetbrains.annotations.NotNull;
import jetbrains.mps.smodel.language.LanguageExtensions;

public class Language extends LanguageRuntime {
  private final SLanguageId myId;

  public Language() {
    myId = SLanguageId.deserialize("b08cef69-3da2-4fad-8be5-0bcfa1a58e33");
  }

  @Override
  public String getNamespace() {
    return "robotassembly";
  }

  @Override
  public int getVersion() {
    return 0;
  }

  public SLanguageId getId() {
    return myId;
  }

  @Override
  protected void fillExtendedLanguages(Collection<SLanguage> extendedLanguages) {
    extendedLanguages.add(MetaAdapterFactory.getLanguage(SLanguageId.deserialize("f3061a53-9226-4cc5-a443-f952ceaf5816"), "jetbrains.mps.baseLanguage"));
  }

  @Override
  protected <T extends ILanguageAspect> T createAspect(Class<T> aspectClass) {
    if (aspectClass == EditorAspectDescriptor.class) {
      return aspectClass.cast(new EditorAspectDescriptorImpl());
    }
    if (aspectClass == StructureAspectDescriptor.class) {
      return aspectClass.cast(new robotassembly.structure.StructureAspectDescriptor());
    }
    if (aspectClass == ConceptPresentationAspect.class) {
      return aspectClass.cast(new ConceptPresentationAspectImpl());
    }
    if (aspectClass == TextGenAspectDescriptor.class) {
      return aspectClass.cast(new robotassembly.textGen.TextGenAspectDescriptor());
    }
    return null;
  }

  @Override
  protected void contribute(@NotNull LanguageExtensions extensions) {
  }
}