There is another option. Right now we have a number of "expressions"
that can only really be used as statements:
a = b
a += b
loop { }
while cond { }
return
...
These all have unit (or bottom) return type. We could require
semicolons after these. At least you would not then be able to write:
if cond { return }
but rather
if cond { return; }
and not
fn foo() -> int { return 22 }
but rather
fn foo() -> int { return 22; }
Niko
On 8/2/12 9:47 AM, Patrick Walton wrote:
On 08/02/2012 09:15 AM, Gareth Smith wrote:
> Thus this is in practice a backwards-compatible change intended to
eliminate a good deal of toe-stubbing.
IMHO the source of the toe-stubbing may be that rust has so many
different ways to return a value:
I'm not sure. The complaints I've seen (see the mailing list thread,
or the bug [1], or various other private/public comments) are
specifically about the trailing semicolon being significant.
It also doesn't seem possible to fix this in the way you suggest.
There are two ways:
1. Require "return", turning Rust back into a statement-oriented
language instead of an expression-oriented one. I think it's too late
to make such a drastic change. Besides, this is likely to make
functional programmers unhappy.
2. Remove "return". This eliminates a huge amount of expressiveness.
Many functional languages don't have "return", but they get around it
with monads or exceptions, neither of which we have good support for.
Also, Perl is an example of a curly-brace language in which both
syntaxes work. JS is related -- it has the notion of a "completion
value" for blocks, although you don't implicitly return the completion
value.
(As an aside, "return" not working inside lambda blocks is an issue,
but that's basically because making it work would either introduce an
unacceptable performance penalty, equivalent to C++ try/catch, or be
inconsistent with the way it works in "for" blocks.)
Patrick
[1]: https://github.com/mozilla/rust/issues/1712
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