The type one path segment names: a field of T, or — where the segment
carries indexes — the element that indexing that field reaches.
NonNullable is applied before stepping into the element, for the reason
TypeAtDotPath applies it between segments: a nullable List is
declared Element[] | undefined, which as a union does not match the array
pattern, and an element of a List that is set is defined. Without it the
index resolved to never and the key fell back to the stored form.
The type one path segment names: a field of
T, or — where the segment carries indexes — the element that indexing that field reaches.NonNullableis applied before stepping into the element, for the reason TypeAtDotPath applies it between segments: a nullable List is declaredElement[] | undefined, which as a union does not match the array pattern, and an element of a List that is set is defined. Without it the index resolved toneverand the key fell back to the stored form.