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Sort DeclAttributeAndRanges Deterministically #26099

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Jul 12, 2019
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Sort DeclAttributeAndRanges Deterministically #26099

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11 changes: 7 additions & 4 deletions lib/IDE/SyntaxModel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1080,10 +1080,13 @@ bool ModelASTWalker::handleAttrRanges(ArrayRef<DeclAttributeAndRange> DeclRanges

SmallVector<DeclAttributeAndRange, 4> SortedRanges(DeclRanges.begin(),
DeclRanges.end());
std::sort(SortedRanges.begin(), SortedRanges.end(),
[&](DeclAttributeAndRange LHS, DeclAttributeAndRange RHS) {
return SM.isBeforeInBuffer(LHS.second.Start, RHS.second.End);
});
std::sort(
SortedRanges.begin(), SortedRanges.end(),
[&](DeclAttributeAndRange LHS, DeclAttributeAndRange RHS) {
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Could you add a comment that the comparison is like this because ranges may overlap along with a FIXME to investigate why there are overlapped ranges in the first place ?

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@gmittert gmittert Jul 12, 2019 •
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I believe it's not that there are overlapping ranges, but rather when comparing something against itself. So... a very specific instance of overlapping ranges.

Given that the ranges shouldn't overlap otherwise, would it be fair to just compare the start of each range rather than both the start and end?

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I see, so a simpler return SM.isBeforeInBuffer(LHS.second.Start, RHS.second.Start); would work as well?

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Yeah, that's what I changed it to. I didn't realize before that the ranges shouldn't overlap otherwise, but that makes sense give that they're source ranges of attributes.

// Since attributes don't overlap it's safe to compare just by the
// range's Start
return SM.isBeforeInBuffer(LHS.second.Start, RHS.second.Start);
});
// Handle duplicate synthesized attributes due to * in @available
auto NewEnd = std::unique(SortedRanges.begin(), SortedRanges.end(),
[&](DeclAttributeAndRange LHS, DeclAttributeAndRange RHS) {
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