Description of the feature request:

Empty depsets are optimized out of providers, but not structs. This can lead to increased memory usage for some code patterns.

Which category does this issue belong to?

Starlark Integration, Starlark Interpreter

What underlying problem are you trying to solve with this feature?

In rules_xcodeproj we marshal a lot of data collected in aspects down the dependency tree. When doing Starlark memory profiling we noticed that creating new empty depset instances would drastically increase our memory usage. So instead we create frozen instances of empty values and use them when possible: https://github.com/MobileNativeFoundation/rules_xcodeproj/blob/31a9e114dac0e20625fb7d9119fe5a117ecb3608/xcodeproj/internal/memory_efficiency.bzl, which helped us reduce our memory usage.

Which operating system are you running Bazel on?

macOS 13.4.1 (c)

What is the output of bazel info release?

release 6.3.2

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

https://bazelbuild.slack.com/archives/CA31HN1T3/p1693484609534579 where @fmeum requested I open this issue.