compiler flag for "preview all"

[Bruce Carneal]

On Tuesday, 30 June 2020 at 01:05:22 UTC, Bruce Carneal wrote:
> On Monday, 29 June 2020 at 23:31:16 UTC, Bruce Carneal wrote:
>> One of the ideas floated at beerconf was that of a single 
>> compiler flag activating all "preview" options.
> [snip]
>>
>> PS: Also at beerconf Stefan Koch opined that turning on all 
>> preview options might not be possible due to incompatibilities 
>> of some sort which, if true, would be an excellent reason for 
>> adding the capability.
>
> Stefan was right.  ldc 1.22.0 seg faults when compiling with 
> all preview flags set, manually, and trivially exercising dip 
> 1008 by itself.
>
> Could be that there are several additional fatal combinations.
>
> I suggest that the compiler writers extend their test suites to 
> exercise at least the "all previews enabled" + small-N-utilized 
> permutations.

Turns out you can trigger the seg fault by just enabling dip 1008 
and dip 1021.

Not sure how many other such preview-combo seg faults are there 
to be isolated and fixed but seems like a systematic sweep of the 
combinations should be part of the compiler test suite.  Playing 
"combinatoric seg fault roulette" doesn't sound like fun for 
anybody.

My guess is that these preview-combo errors can be isolated to 
the front end.