/// Tries to remap the location from a previous snapshot to the latest one.
static llvm::Optional<std::pair<unsigned, unsigned>>
tryRemappingLocToLatestSnapshot(SwiftLangSupport &Lang,
std::pair<unsigned, unsigned> Range,
StringRef Filename,
ArrayRef<ImmutableTextSnapshotRef> PreviousASTSnaps) {
ImmutableTextSnapshotRef LatestSnap;
if (auto EditorDoc = Lang.getEditorDocuments().findByPath(Filename))
LatestSnap = EditorDoc->getLatestSnapshot();
if (!LatestSnap)
return Range;
for (auto &PrevSnap : PreviousASTSnaps) {
if (PrevSnap->isFromSameBuffer(LatestSnap)) {
if (PrevSnap->getStamp() == LatestSnap->getStamp())
return Range;
auto OptBegin = mapOffsetToNewerSnapshot(Range.first,
PrevSnap, LatestSnap);
if (!OptBegin.hasValue())
return None;
auto OptEnd = mapOffsetToNewerSnapshot(Range.first+Range.second,
PrevSnap, LatestSnap);
if (!OptEnd.hasValue())
return None;
return std::make_pair(*OptBegin, *OptEnd-*OptBegin);
}
}
return Range;
}
bool canUseASTWithSnapshots(
ArrayRef<ImmutableTextSnapshotRef> Snapshots) override {
if (!TryExistingAST) {
LOG_INFO_FUNC(High, "will resolve using up-to-date AST");
return false;
}
// If there is an existing AST and the offset can be mapped back to the
// document snapshot that was used to create it, then use that AST.
// The downside is that we may return stale information, but we get the
// benefit of increased responsiveness, since the request will not be
// blocked waiting on the AST to be fully typechecked.
ImmutableTextSnapshotRef InputSnap;
if (auto EditorDoc = Lang.getEditorDocuments().findByPath(InputFile))
InputSnap = EditorDoc->getLatestSnapshot();
if (!InputSnap)
return false;
auto mappedBackOffset = [&]()->llvm::Optional<unsigned> {
for (auto &Snap : Snapshots) {
if (Snap->isFromSameBuffer(InputSnap)) {
if (Snap->getStamp() == InputSnap->getStamp())
return Offset;
auto OptOffset = mapOffsetToOlderSnapshot(Offset, InputSnap, Snap);
if (!OptOffset.hasValue())
return None;
// Check that the new and old offset still point to the same token.
StringRef NewTok = getSourceToken(Offset, InputSnap);
if (NewTok.empty())
return None;
if (NewTok == getSourceToken(OptOffset.getValue(), Snap))
return OptOffset;
return None;
}
}
return None;
};
auto OldOffsetOpt = mappedBackOffset();
if (OldOffsetOpt.hasValue()) {
Offset = *OldOffsetOpt;
PreviousASTSnaps.append(Snapshots.begin(), Snapshots.end());
LOG_INFO_FUNC(High, "will try existing AST");
return true;
}
LOG_INFO_FUNC(High, "will resolve using up-to-date AST");
return false;
}
explicit Implementation(SwiftLangSupport &LangSupport)
: EditorDocs(LangSupport.getEditorDocuments()),
Stats(LangSupport.getStatistics()),
RuntimeResourcePath(LangSupport.getRuntimeResourcePath()) {}
