dplyr 0.7.3

• Fixed protection error that occurred when creating a character column using grouped mutate() (#2971).

• Fixed a rare problem with accessing variable values in summarise() when all groups have size one (#3050).

• Fixed rare out-of-bounds memory write in slice() when negative indices beyond the number of rows were involved (#3073).

• select(), rename() and summarise() no longer change the grouped vars of the original data (#3038).

• nth(default = var), first(default = var) and last(default = var) fall back to standard evaluation in a grouped operation instead of triggering an error (#3045).

• case_when() now works if all LHS are atomic (#2909), or when LHS or RHS values are zero-length vectors (#3048).

• case_when() accepts NA on the LHS (#2927).

• Semi- and anti-joins now preserve the order of left-hand-side data frame (#3089).

• Improved error message for invalid list arguments to bind_rows() (#3068).

• Grouping by character vectors is now faster (#2204).

• Fixed a crash that occurred when an unexpected input was supplied to
  the call argument of order_by() (#3065).