read_csv coerces character column to double, but no NA?

[icj]

In readr 0.1.1, read_csv does the following:

# with readr 0.1.1
file <- "X1\n1\n2\n2X"
read_csv(file)

# Source: local data frame [3 x 1]
# 
#      X1
#   (chr)
#1     1
#2     2
#3    2X

But in readr 0.2.2, read_csv does something unexpected:

# with readr 0.2.2
file <- "X1\n1\n2\n2X"
read_csv(file)

# Source: local data frame [3 x 1]
# 
#      X1
#   (dbl)
#1     1
#2     2
#3     2

Seems like the 2X should have been NA if it thought it was a numeric column. Subbing it to 2 could be dangerous.

[hadley]

Hmmm, the numeric guesser is being too aggressive. I'll have another look at it.

[hadley]

Duplicate of #308