Address review comments.

Author: mcol

R/fread.R

@@ -55,7 +55,7 @@ yaml=FALSE, tmpdir=tempdir(), tz="UTC")
     else stopifnot( nchar(sep)==1L )  # otherwise an actual character to use as sep
   }
   stopifnot( is.character(dec), length(dec)==1L)
-  if (!is.na(dec) && dec == "auto") dec = "" else stopifnot(nchar(dec) == 1L)
+  if (identical(dec, "auto")) dec = "" else stopifnot(nchar(dec) == 1L)
   # handle encoding, #563
   if (length(encoding) != 1L || !encoding %chin% c("unknown", "UTF-8", "Latin-1")) {
     stopf("Argument 'encoding' must be 'unknown', 'UTF-8' or 'Latin-1'.")

inst/tests/tests.Rraw

@@ -21607,4 +21607,4 @@ test(2370.4, yearmon("2016-08-03 01:02:03.45", format="character"), "2016M08")
 test(2370.5, yearmon(NA, format="character"), NA_character_)
 
 ## validation of dec argument
-test(7737.1, fread(input = "whatever.csv", dec = NA_character_), error="nchar(dec) == 1L is not TRUE")
+test(7737.1, fread(input = "whatever.csv", dec = NA_character_), error=base_messages$stopifnot("nchar(dec) == 1L"))