dimnames(X)[[2]] <- foo fails (PR#1122)

Since this works in recent S-PLUS and is not in the FAQ as a difference, I
presume it is an unintentional one.  If it is intentional, this is for the
wishlist that this be removed.

S-PLUS (6.0)

X <- matrix(1:4, 2, 2)
dimnames(X)[[2]] <- letters[1:2]
X

     a b
[1,] 1 3
[2,] 2 4

R 1.3.1

X <- matrix(1:4, 2, 2)
dimnames(X)[[2]] <- letters[1:2]

Error: more elements supplied than there are to replace

colnames(X) <- 1:2
dimnames(X)[[2]] <- letters[1:2]
X

     a b
[1,] 1 3
[2,] 2 4

which is none too obvious an error message, and somewhat inconsistent.

x<-NULL
x[[2]]<- letters[1:2]

x<-NULL
x[[2]]<- letters[1:2]
x

x<-NULL
x[[2]]<-"1"
x

 x <- matrix(1:2,2)
 dimnames(X)[[2]] <- "a"