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The ‘"source"’ attribute (which has not been added by R since before R version 2.14.0) is no longer treated as special.
An experimental function ‘returnValue()’ has been added to give ‘on.exit()’ code access to a function's return value for debugging purposes.
‘drop1()’ failed if the ‘scope’ argument had no variables to drop. (PR#15935)
‘edit()’ (and hence ‘fix()’ failed if an object had a non-character attribute named ‘"source"’ (an attribute that had been used in R prior to version 2.14.0).