Port ?? binary operator emit

[weswigham]

Which is to say, the smaller half of the es2020 transform. The other half being ?..

[Copilot]

Pull Request Overview

This PR ports support for emitting the ?? (nullish coalescing) operator in the Go-based native transformer/printer. It introduces a new transformer for ??, updates the AST and factory to recognize and print long-form nullish checks, adjusts how parameters with default values/binding patterns are handled during emit, and brings baseline snapshots into alignment.

• Added createNotNullCondition helper and a nullishCoalescingTransformer to handle ?? rewrites.
• Updated NodeFactory and EmitContext to support strict equality, type checks, and hoisting defaults for parameters.
• Regenerated many .js baselines to use the long-form x !== null && x !== void 0 ? x : y pattern.

Reviewed Changes

Copilot reviewed 101 out of 101 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/transformers/estransforms/utilities.go	Added createNotNullCondition to build nullish check nodes
internal/transformers/estransforms/nullishcoalescing.go	Implemented transformer for ?? to conditional expressions
internal/printer/factory.go	Added NewStrictEqualityExpression and NewTypeCheck
internal/printer/emitcontext.go	Enhanced parameter-scoped hoisting for default assignments
internal/ast/ast.go	Updated token facts to mark ?? as SubtreeContainsNullishCoalescing

Comments suppressed due to low confidence (2)

internal/transformers/estransforms/nullishcoalescing.go:13

• There are no unit tests for the new nullishCoalescingTransformer. Adding a minimal Go-level test for ?? emission would ensure future changes don’t regress this behavior.

func (ch *nullishCoalescingTransformer) visit(node *ast.Node) *ast.Node {

internal/transformers/estransforms/utilities.go:22

• The invert parameter is never used (always called with false). Consider removing it or documenting its intended use to simplify this helper.

func createNotNullCondition(emitContext *printer.EmitContext, left *ast.Node, right *ast.Node, invert bool) *ast.Node {