Fixed control flow Analysis of aliased discriminants with parenthesized initializers

[Andarist]

fixes #61784

[Copilot]

Pull Request Overview

This PR fixes an issue where discriminant properties aliased through parenthesized or destructured initializers weren't correctly recognized in control-flow analysis.

• Added comprehensive tests covering both direct and parenthesized/destructured alias patterns.
• Refactored the alias resolution logic in the type checker to use a helper that skips parentheses.
• Introduced getCandidateVariableDeclarationInitializer to centralize initializer extraction.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
tests/cases/conformance/controlFlow/controlFlowAliasing2.ts	New tests for aliased discriminants with various initializer forms
tests/baselines/reference/controlFlowAliasing2.symbols	Baseline update for the new conformance tests
src/compiler/checker.ts	Extracted initializer logic into a helper and updated alias-matching branches

Comments suppressed due to low confidence (1)

src/compiler/checker.ts:29266

• [nitpick] Consider renaming this helper to something shorter like getInitializerSkippingParens or extractInitializer for improved readability.

function getCandidateVariableDeclarationInitializer(node: Node) {

[Harpush]

Any chance for this passing?

[jakebailey]

@typescript-bot test it

[typescript-bot]

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
test top400	✅ Started	✅ Results
user test this	✅ Started
run dt	✅ Started	✅ Results
perf test this faster	✅ Started

[typescript-bot]

Hey @jakebailey, the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

[typescript-bot]

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/61788/merge:

Everything looks good!