[FrankHB]

This is simply not acceptable because it would silently break too much code. Parameter passing in C++ used to mean copy, not move.

Perhaps a more important rule is that id-expressions should mean lvalues, not xvalues. Note that even expressions of rvalue references are not xvalues in such contexts. So, making something to-be-moved visually different from others is quite intentional.

Alternatively, to prevent use-after-move cases by additional syntaxes with typechecking rules (like Rust) can be a good idea, but it also does not work here. And C++ still lacks destructive move. (Note this has been considered at the very beginning of the design. Sadly it does not easily interact well with other features. See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n137...)