Segfault caused by broken data.frame

[TobiasMadsen]

I was a bit unsure whether to post this issue or if it's a case of "gunshot injury of foot stemming from aiming at foot and pulling the trigger". Anyway the following code produces a segfault

library(dplyr)
df <- data.frame(x1 = rep(1:3, times = 3), x2 = 1:9)
df$x3 <- df %>% mutate(x3 = x2) # Should have been df <- df %>% mutate(x3 = x2)
# df$x3 is now a data.frame
df <- df %>% group_by(x1) %>% summarise(x4 = mean(x3))