+ leftmargin=\parindent}
+
+% The optional argument here gets stuffed into the \thiscase macro, to
+% be called by pcases when it creates this list item. The \hfill is a
+% hack intended to force the proof to start on a new line, rather than
+% right after the colon. A \newline where the \hfill is does not work,
+% so we consume the rest of the line instead.