sonarjs/no-unused-collection crash on Svelte use: directive

Minimal reproduction for a crash in eslint-plugin-sonarjs rule sonarjs/no-unused-collection (S4030) when linting a Svelte file that contains a use: action directive.

Bug

The rule crashes with TypeError: Cannot read properties of null (reading 'type') when a Svelte file with <script lang="ts"> (parsed via @typescript-eslint/parser) contains:

1. A use: directive referencing a function declaration (not an arrow function)
2. A variable passed as the directive expression: <div use:fn={variable}></div>

The variable's type doesn't matter — a plain let x = 0 is enough. The crash is unrelated to collections despite being in the no-unused-collection rule.

Reproduce

npm install
npm test

Expected: no crash (the rule should either report or silently pass). Actual:

TypeError: Cannot read properties of null (reading 'type')
Occurred while linting App.svelte:1
Rule: "sonarjs/no-unused-collection"
    at isElementWrite (eslint-plugin-sonarjs/cjs/helpers/ast.js:191:30)
    at isRead (eslint-plugin-sonarjs/cjs/S4030/rule.js:146:46)
    at isUnusedCollection (eslint-plugin-sonarjs/cjs/S4030/rule.js:112:18)
    ...

Possible root cause

From reading the source, the issue appears to be in isElementWrite (helpers/ast.js), which accesses statement.expression.type without guarding against expression being null. The S4030 rule's isRead function calls findFirstMatchingAncestor looking for a node with type === 'ExpressionStatement' with no boundary types. With the Svelte+TS parser, this traversal appears to reach a synthetic AST node that satisfies the type check but has a null .expression property.

S3516 (no-invariant-returns) uses the same isElementWrite helper but doesn't fail in the same way, possibly because it includes FUNCTION_NODES in its ancestor search predicate, which would prevent the traversal from reaching the problematic node. If so, the missing null guard in isElementWrite could affect other callers if their traversal predicates change in the future.

Testing a specific version

To check if a fix has landed in a newer release:

# test latest
npm run test:version

# test a specific version
VERSION=4.1.0 npm run test:version

Versions (pinned)