Narrow by constant element access callees

[Andarist]

fixes #62247

[Copilot]

Pull Request Overview

This PR implements support for narrowing by type predicates when using element access expressions with constant arguments, addressing issue #62247. The fix allows TypeScript to properly narrow types when calling type predicate methods through computed property access with symbol keys.

Key Changes:

• Enhanced type narrowing logic to support element access expressions with constant arguments in addition to property access expressions
• Added comprehensive test coverage for the new functionality

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/compiler/checker.ts	Updated type narrowing condition to include element access expressions with constant arguments
src/compiler/binder.ts	Extended narrowable reference detection to support element access expressions
tests/cases/compiler/narrowByTypePredicateFromElementAccessExpression1.ts	Added test case demonstrating type narrowing with symbol-based element access
tests/baselines/reference/narrowByTypePredicateFromElementAccessExpression1.types	Generated baseline showing expected type information
tests/baselines/reference/narrowByTypePredicateFromElementAccessExpression1.symbols	Generated baseline showing expected symbol resolution

Comments suppressed due to low confidence (1)

[typescript-bot]

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

• For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
• Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
• Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate