Review ported code from formatter

[DanielRosenwasser]

Original code:

const parent = findPrecedingToken(tokenInfo.end, sourceFile, enclosingNode)?.parent || previousParent!;

https://github.com/microsoft/TypeScript/blob/9d364978d3e8e4de01bb2bec8083b58c1f710232/src/services/formatting/formatting.ts#L567

New code:

parent := astnav.FindPrecedingToken(w.sourceFile, tokenInfo.Loc.End())
if parent == nil {
	parent = w.previousParent
}

typescript-go/internal/format/span.go

Lines 304 to 307 in 0527802

	parent := astnav.FindPrecedingToken(w.sourceFile, tokenInfo.Loc.End())
	if parent == nil {
	parent = w.previousParent
	}

Looks like we at least need something like

- parent := astnav.FindPrecedingToken(w.sourceFile, tokenInfo.Loc.End())
+ var parent *ast.Node
+ prevToken := astnav.FindPrecedingToken(w.sourceFile, tokenInfo.Loc.End())
+ if prevToken != nil {
+ 	parent = prevToken.Parent
+ }
  if parent == nil {
  	parent = w.previousParent
  }

[weswigham]

Fixed by #2370 - https://github.com/microsoft/typescript-go/pull/2370/files#diff-57e4e12e0839091e4dde6c1f5e10e1438c3d3cd4f4eabdd7ea07530f0aac185dR306