parse() does not complain for not finished strings?

Hello,
parse() is supposed to detect incomplete instructions, isn't it?
For instance:

# Correct code
msg <- 'log(10)'
mc <- textConnection(msg)
parse(mc)

expression(log(10))

close(mc)

# Now, an incomplete code
msg <- 'log('
mc <- textConnection(msg)
parse(mc)

Error in parse(mc) : unexpected end of input at
2: log(

close(mc)

# Now, another incomplete code (character string not finished)
msg <- 'text <- "some incomplete string'
mc <- textConnection(msg)
parse(mc)

expression(text <- "some incomplete string\n")

close(mc)

I don't understand why parse() does not complain in this third case, and
why it "finishes" my string and adds a '\n' at its end. Does anybody
could explain me,... or is this a bug?
Many thanks.

Philippe Grosjean