Return an empty list when item is not present in the attributes table

[momvart]

Fixes #128145

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[petrochenkov]

The assert is there for a reason, it's expected that attributes (and many other properties) are never queried for ids for which they are not encoded.

If your code need to query attributes for all DefIds (in a third party tool, I assume, this situation shouldn't occur in the compiler), then it should filter ids with something like fn should_encode_attrs first.

[momvart]

then it should filter ids with something like fn should_encode_attrs first.

Thanks. Didn't know about it. Is any public equivalent of it available?

The assert is there for a reason, it's expected that attributes (and many other properties) are never queried for ids for which they are not encoded.

I agree and for an internal function this is probably the best.

However, for a public API in TyCtxt that supports both local and external ids, such expectation is not obvious. Can't we change/introduce the API to something like opt_get_attrs to return None if an item is not expected to have attributes?

[petrochenkov]

Most decoder interfaces will currently panic on missing data, I'd prefer to not add "optional" interfaces for all of those just for third-party tools.

The issue can be worked around by using a condition like tcx.def_kind(def_id) != DefKind::AnonConst or copypasting the whole fn should_encode_attrs (but that is unlikely to be useful if you only process def ids with bodies).