Declaration in expression - Re: Python-like Use of the Comma Expression

[Nick Treleaven]

On Thursday, 10 August 2023 at 21:38:25 UTC, Basile B. wrote:
> whe have var decl syntax for `if`, since recently for `while` 
> too... It's pretty clear that "in situ" variable decls are 
> required...unless D continues on making special cases.

For `if (auto x = expr)`, the scope of `x` includes the 
*ThenStatement*.
For `if ((auto x = expr) || b)`, `x` can have similar scope.
For `if (b && (auto x = expr))`, `x` can have similar scope.
I think the above two cases could be supported in D.

For `if (b || (auto x = expr))`, `x` may be uninitialized if it 
is accessible in the *ThenStatement*. Does Styx forbid that and 
similar cases?

Also for `if (b || ((auto x = expr) && x.b))`, `x` is safely used 
but it may be uninitialized if its scope extends to the 
*ThenStatement*.