(SymbolGraphGen) orphaned stdlib symbol 'Unicode._NFD.Iterator.next'

[tayloraswift]

SymbolGraphGen on swift 5.8 currently omits the Unicode._NFD and Unicode._NFD.Iterator symbols when dumping the stdlib symbol graph, but for some reason it emits a symbol for Unicode._NFD.Iterator.next (ss7UnicodeO4_NFDV8IteratorV4nextAB6ScalarVSgyF), and a memberOf edge connecting it to the nonexistent Unicode._NFD.Iterator symbol (ss7UnicodeO4_NFDV8IteratorV). this causes downstream tooling to error.

this can be reproduced by dumping the stdlib symbol graph with:

swift symbolgraph-extract \
    -target x86_64-unknown-linux-gnu \
    -minimum-access-level internal \
    -output-dir <output dir> \
    -skip-inherited-docs \
    -emit-extension-block-symbols \
    -pretty-print \
    -module-name Swift

note that Unicode._NFD would normally appear (despite being underscored) because of -minimum-access-level internal, it is most likely hidden because it is SPI.