  SN2017hcc was remarkable for being a nearby and strongly polarized
superluminous TypeIIn supernova (SN). We obtained high-resolution echelle
spectra that we combine with other spectra to investigate its line profile
evolution. All epochs reveal narrow P~Cygni components from pre-shock
circumstellar material (CSM), indicating an axisymmetric outflow from the
progenitor of 40-50 km/s. Intermediate-width and broad components exhibit the
classic evolution seen in luminous SNe~IIn: symmetric Lorentzian profiles from
pre-shock CSM lines broadened by electron scattering at early times,
transitioning at late times to multi-component, irregular profiles coming from
the SN ejecta and post-shock shell. As in many SNe~IIn, profiles show a
progressively increasing blueshift, with a clear flux deficit in red wings of
the intermediate and broad velocity components after day 200. This blueshift
develops after the continuum luminosity fades, and in the intermediate-width
component, persists at late times even after the SN ejecta fade. In SN2017hcc,
the blueshift cannot be explained as occultation by the SN photosphere,
pre-shock acceleration of CSM, or a lopsided explosion or CSM. Instead, the
blueshift arises from dust formation in the post-shock shell and in the SN
ejecta. The effect has a wavelength dependence characteristic of dust,
exhibiting an extinction law consistent with large grains. Thus, SN2017hcc
experienced post-shock dust formation and had a mildly bipolar CSM shell,
similar to SN2010jl. Like other superluminous SNeIIn, the progenitor lost
around 10Msun due to extreme eruptive mass loss in the decade before exploding.
