Always set synthetic position when deep cloning

[gabritto]

Fixes an out of bounds crash found when compiling an internal project.

We weren't setting (-1, -1) as a position for non-leaf nodes when deep cloning them. As a result, we'd later use those positions to access a file's text that wasn't the file for the cloned node, so the positions were out of the file text's bounds.

The diff for some compiler tests increased because we now seem to omit a comma during emit, but I think this is a problem that can be addressed later.

[weswigham]

Do we need to copy the hasTrailingComma node list member?

[gabritto]

Do we need to copy the hasTrailingComma node list member?

Uh, right, that's what's causing the diffs. That's a method now in Corsa, and it skips synthetic nodes and checks positions to determine the result. We could set up positions when cloning to preserve this (maybe set end to -2 on the last node of the list if it had a trailing comma?), I think. I'll try doing that and see if it works.

[Copilot]

Pull Request Overview

This PR fixes an out-of-bounds crash that occurred when compiling an internal project by ensuring that synthetic positions (-1, -1) are properly set when deep cloning AST nodes. The crash was happening because cloned nodes weren't getting synthetic positions, leading to attempts to access file text at invalid positions.

Key changes:

• Modified deep clone visitor to set synthetic positions for all cloned nodes and lists
• Updated HasTrailingComma() logic to properly handle synthetic positions
• Added a test case to prevent regression of this cross-file node scenario

Reviewed Changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
testdata/tests/cases/compiler/declarationEmitNoCrashOnCrossFileNode.ts	New test case demonstrating the crash scenario with cross-file imports and destructuring parameters
internal/ast/deepclone.go	Enhanced deep clone visitor to set synthetic positions (-1, -1) for all cloned nodes and lists when syntheticLocation flag is true
internal/ast/ast.go	Simplified HasTrailingComma() logic by removing synthetic position checks that were causing issues
testdata/baselines/reference/submodule/compiler/*.diff	Test baseline updates showing changes in destructuring parameter comma handling
testdata/baselines/reference/compiler/declarationEmitNoCrashOnCrossFileNode.*	New test baselines for the crash prevention test