Update static exclusivity diagnostics to not suggest copying to a local
when a call to swapAt() should be used instead. We already emit a FixIt in
this case, so don't suggest an an helpful fix in the diagnostic.
rdar://problem/32296784
Remove the descriptive decl kind (since with subpaths it is not correct and
cannot represent a tuple element) and change "simultaneous" to "overlapping"
in order to lower the register slightly and avoid connoting threading.
For example, for the following:
takesTwoInouts(&x.f, &x.f)
the diagnostic will change from
"simultaneous accesses to var 'x.f', but modification requires exclusive access;
consider copying to a local variable"
to
"overlapping accesses to 'x.f', but modification requires exclusive access;
consider copying to a local variable"
Relax the static enforcement of exclusive access so that we no longer diagnose
on accesses to separate stored structs of the same property:
takesInout(&s.f1, &s.f2) // no-warning
And perform the analogous relaxation for tuple elements.
To do this, track for each begin_access the projection path from that
access and record the read and write-like modifications on a per-subpath
basis.
We still warn if the there are conflicting accesses on subpaths where one is
the prefix of another.
This commit leaves the diagnostic text in a not-so-good shape since we refer
to the DescriptiveDeclKind of the access even describing a subpath.
I'll fix that up in a later commit that changes only diagnostic text.
https://bugs.swift.org/browse/SR-5119
rdar://problem/31909639
Update the static diagnostics when enforcing exclusive access to suggest adding
a local variable. The new diagnostic text is:
"simultaneous accesses to var 'a', but modification requires exclusive
access; consider copying to a local variable"
