[Rd] side-effect of calling functions via `::`

[Simon Barthelmé]

Dear list

I'm not sure whether this is a bug or an unavoidable consequence of the 
way packages are loaded, but there can be surprising side effects of 
calling a function via package::function. Here's an example using the 
formula.tools package:

form <- a ~ b
as.character(form)
formula.tools::lhs(form)
as.character(form)

The first call to as.character returns:
[1] "~" "a" "b"
The second returns:
[1] "a ~ b"

The reason being that formula.tools has:
S3method(as.character,formula)
in its namespace, which quietly supersedes the default one. In my case 
it led to a bug that was rather hard to track down because it looked 
like non-deterministic behaviour.
Shouldn't there at least be a warning about such side effects, the way 
library() tells you about masking?

Best

Simon Barthelme