Suggestion
🔍 Search Terms
union distribute short-circuit performance
✅ Viability Checklist
My suggestion meets these guidelines:
⭐ Suggestion
Andrew Casey (@amcasey) and I were discussing #47481 and he had an interesting observation. Consider this program:
type HugeUnion1 = "a" | "b" | "c" | "d" | ... [10,000 more];
type HugeUnion2 = "q" | "r" | "s" | "t" | ... [10,000 more];
type Square<T, U> = T extends U ? true : false;
type M = Square<T, U>;
Naively, when evaluating M, we need to check if every member of HugeUnion1 is present in HugeUnion2. However, let's say we saw this (in the sorted form):
type HugeUnion1 = "a" | "q" | ... [10,000 more];
type HugeUnion2 = "a" | ... [10,000 more which do not include 'q'];
After evaluating "a", we have a true. After evaluating "q", we have a false. We can skip the rest of the list since no subsequent result will change the answer (because T does not appear in the conditional result)
Moreover, if instead of false we had never, we could immediately stop after seeing true, since true | never is just true
Suggestion
🔍 Search Terms
union distribute short-circuit performance
✅ Viability Checklist
My suggestion meets these guidelines:
⭐ Suggestion
Andrew Casey (@amcasey) and I were discussing #47481 and he had an interesting observation. Consider this program:
Naively, when evaluating
M, we need to check if every member ofHugeUnion1is present inHugeUnion2. However, let's say we saw this (in the sorted form):After evaluating
"a", we have atrue. After evaluating"q", we have afalse. We can skip the rest of the list since no subsequent result will change the answer (becauseTdoes not appear in the conditional result)Moreover, if instead of
falsewe hadnever, we could immediately stop after seeingtrue, sincetrue | neveris justtrue