DIP 1003 Formal Review

[Timon Gehr via Digitalmars-d]

On 25.05.2017 20:57, MysticZach wrote:
> On Thursday, 25 May 2017 at 11:49:47 UTC, MysticZach wrote:
>> ...there is no known possibility of semantic confusion between the two 
>> potential uses of `body`,
> 
> I spoke too soon. I found a place where such semantic ambiguity is 
> possible. It can only occur in interface declarations, and will not 
> exist in any currently compilable D code, as it requires `body` to be an 
> identifier to be legal in the first place.
> 
> Currently, the only place in D where you can declare a function that has 
> a contract, but no body, is in an interface. D syntax, it turns out, 
> does not require a semicolon at the end of such declarations. 
> Referencing https://dlang.org/spec/interface.html#interface-contracts we 
> have:
> 
> interface I
> {
>      int foo(int i)
>      in { assert(i); } // <-- no semicolon required
> 
>      void bar();
> }
> 
> Therefore, with `body` as an identifier, you might have this ambiguity:
> 
> struct body {}
> 
> interface I {
>    int foo(int i)
>    in { assert(i); }
> 
>    body bar();
> }
> 
> The ambiguity is fixable by modifying the parser to look ahead after 
> `body` for `{`. Since virtual interface functions are not even allowed 
> to have bodies, if it finds `{`, then `body` should be interpreted as a 
> keyword, and an error issued. In all other cases `body` should be 
> interpreted as an identifier.
> 
> This is not a hard problem, but it is indeed a semantic ambiguity, so it 
> bears mentioning.

There is no ambiguity, because only one valid interpretation exists.