Sampling pure tone sine waves
In contrast to common misunderstanding, aliasing does not affect the process of sampling, rather it affects the process of reconstruction. i.e., the samples themselves do not contain error, but their interpretation at the reconstruction (or anything related with it) will be in error.
So, if you sample a sine wave $$x(t) = A \sin( 2 \pi f_0 t + \theta) $$ at a sampling frequency of $F_s = f_0$, (which is undersampled according to Nyquist-Shannon sampling theorem for bandlimited signals), then your samples will be $$ x[n] = A \sin(\theta) $$ a constant signal! When reconstructed back into continuous waveform at the interpolator output, you will get a DC signal, $x(t) = A \sin(\theta)$, as opposed to the original sine wave.
The error is due to the false assumption at the interpolation stage that those samples $x[n]$ came from an original continuous-time signal which was band-limited to $f_0/2$, Nyquist frequency of sampling frequency $f_0$, which is not the case in reality.