D mentioned on Rust discussions site

[Patrick Schluter]

On Saturday, 23 May 2020 at 02:26:38 UTC, Walter Bright wrote:
> On 5/22/2020 12:08 AM, Araq wrote:
>> [x] Users had to patch every function in order to get type 
>> safety. Check.
>
> They didn't have to change anything. The following code 
> compiles today on gcc:
>
>     foo(i, j) { return i + j; }

It does not compile in C99.

Old style declarations and implicit int are forbidden in C99.