Rust: expand attribute macros on AssocItem

[redsun82]

It turned out that #19334 was not covering the case of items in Impl or Trait blocks, because internally those are AssocItem instances rather than Item ones. This covers that case.

[Copilot]

Pull Request Overview

This PR generalizes attribute-macro expansions to both top-level Items and associated items (AssocItem) by introducing a new ExpandableItem type and wiring it through the schema, extractor, and QL libraries.

• Introduce ExpandableItem in the AST schema and annotate both Item and AssocItem as bases
• Update the DB scheme to define @expandable_item and replace the old item_attribute_macro_expansions relation
• Enhance the Rust extractor (base.rs) to pre- and post-emit attribute expansions for AssocItem as well as Item

Reviewed Changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
rust/schema/prelude.py	Adds new ExpandableItem ASTNode
rust/schema/annotations.py	Annotates AssocItem & Item to inherit from ExpandableItem
rust/ql/lib/rust.dbscheme	Defines @expandable_item, removes old relation, re-adds @assoc_item later
rust/ql/lib/codeql/rust/elements/ExpandableItem*.qll	Generates public and internal QLL wrappers for ExpandableItem
rust/ql/lib/codeql/rust/elements/Item.qll & AssocItem.qll	Switch imports to use ExpandableItem
rust/extractor/src/translate/base.rs	Extends translator macros and methods to handle AssocItem expansions
rust/ql/integration-tests/macro-expansion	Updates expected outputs and test fixtures for assoc-item expansions
rust/ql/lib/upgrades/.../upgrade.properties	Adds upgrade to rename the expansion relation
rust/ql/lib/downgrades/.../downgrade.ql	Provides downgrade path

Comments suppressed due to low confidence (1)

rust/extractor/src/translate/base.rs:708

• The return type was changed to Option<Label<generated::MacroCall>>, but callers in the pre‐emit and post‐emit macros expect labels for Item or AssocItem. This mismatch may lead to compilation errors—consider restoring the original Label<generated::Item> return type or updating the macros to handle MacroCall labels explicitly.

pub(crate) fn prepare_item_expansion(