add sanity check for is(,class2)

git-svn-id: https://svn.r-project.org/R/trunk@81549 00db46b3-68df-0310-9c12-caf00c1e9a41
wch · Jan 22, 2022 · e0fa9f3 · e0fa9f3
1 parent b048065
commit e0fa9f3
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Showing 2 changed files with 5 additions and 3 deletions.
diff --git a/doc/NEWS.Rd b/doc/NEWS.Rd
@@ -173,8 +173,9 @@
       three numeric vectors is a surprisingly common error.
 
       \item \code{mean()}, \code{rank()}, \code{which},
-      \code{barplot()}, \code{contour()} and \code{polygon()} have more
-      robust sanity checks on some of their arguments.
+      \code{barplot()}, \code{contour()}, \code{polygon()}
+      and \code{methods::is()}
+      have more robust sanity checks on some of their arguments.
     }
   }
 

diff --git a/src/library/methods/R/is.R b/src/library/methods/R/is.R
@@ -1,7 +1,7 @@
 #  File src/library/methods/R/is.R
 #  Part of the R package, https://www.R-project.org
 #
-#  Copyright (C) 1995-2021 The R Core Team
+#  Copyright (C) 1995-2022 The R Core Team
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -28,6 +28,7 @@ is <- function(object, class2)
         class1 <- class1[[1L]]
     if(missing(class2))
         return(extends(class1))
+    stopifnot(length(class2) == 1L)
     class1Def <- getClassDef(class1)
     class2Def <- NULL
     if(!is.character(class2)) {