Use accessors on Node instead of casts and field accesses

[ahejlsberg]

With this PR we use accessors on Node instead casts and field accesses whenever possible. For example, an expression like

exportClause.AsNamedExports().Elements.Nodes

simply becomes

exportClause.Elements()

This PR touches a lot of code but doesn't alter any behavior. However, a number of previously distinct code branches are merged and duplicate helpers are eliminated.

[Copilot]

Pull Request Overview

This PR refactors the codebase to use accessor methods on Node instead of direct type casts and field accesses. For example, exportClause.AsNamedExports().Elements.Nodes becomes exportClause.Elements(). The changes are extensive but mechanical, improving code readability and maintainability without altering behavior.

Key Changes:

• Added new accessor methods in internal/ast/ast.go (StatementList(), Statement(), ElementList(), PostfixToken(), QuestionToken())
• Replaced direct field accesses with accessor methods across the entire codebase
• Consolidated duplicate code patterns (e.g., combining multiple case statements that use the same accessor)

Reviewed Changes

Copilot reviewed 58 out of 58 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/ast/ast.go	Added new accessor methods for common node operations
internal/ast/utilities.go	Refactored to use accessors, removed obsolete helper functions
internal/binder/binder.go	Updated to use accessors throughout binding logic
internal/binder/nameresolver.go	Simplified name resolution using accessors
internal/checker/checker.go	Extensive refactoring to use accessors in type checking
internal/checker/utilities.go	Removed duplicate helper functions, using accessors instead
internal/parser/parser.go	Updated parsing logic to use accessors
internal/transformers/*	All transformer files updated to use accessors
internal/printer/*	Printer logic refactored to use accessors
internal/ls/*	Language service files updated to use accessors
internal/tsoptions/*	Config parsing updated to use accessors