C#: Add ObjectInitMethod as enclosing callable for the instance initializers.

[aschackmull]

I believe this was an oversight in #20922.

[Copilot]

Pull request overview

This PR addresses an oversight from #20922 by ensuring instance member initializer assignments are associated with the extractor-synthesized ObjectInitMethod as their enclosing callable (improving enclosing-callable / CFG scoping behavior around instance initializers).

Changes:

• Move/centralize the “object initializer initializes assignment” relation onto ObjectInitMethod via a new initializes(AssignExpr) predicate.
• Update CFG scoping logic to use ObjectInitMethod.initializes directly.
• Update enclosing-callable computation to treat initializer assignment expressions as enclosed by the corresponding ObjectInitMethod.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
csharp/ql/lib/semmle/code/csharp/controlflow/internal/ControlFlowGraphImpl.qll	Switches initializer ordering/scoping logic to use ObjectInitMethod.initializes instead of a local helper predicate.
csharp/ql/lib/semmle/code/csharp/ExprOrStmtParent.qll	Extends enclosing-callable relation to include initializer assignment expressions for ObjectInitMethod.
csharp/ql/lib/semmle/code/csharp/Callable.qll	Introduces InitializedInstanceMember and adds ObjectInitMethod.initializes(AssignExpr) to expose the relationship as a reusable API.

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[hvitved]

LGTM, but some tests are failing and we also need a DCA run.

[aschackmull]

LGTM, but some tests are failing and we also need a DCA run.

The test changes look correct to me, so I've pushed a commit accepting them. I'll start dca now.

[aschackmull]

Dca shows a few additional alerts - they look plausibly reasonable to me. And there's no impact on performance.