public void changeResultType(TypeBearer type, LocalItem local) {
    setResult(RegisterSpec.makeLocalOptional(getResult().getReg(), type, local));
  }
Changes the result type. Used during phi type resolution

@param type {@code non-null;} new TypeBearer
@param local {@code null-ok;} new local info, if available
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/PhiInsn.java