old := *r.Expr
		*r.Expr = expr

		// Record source-level edit for cgo output.
		if !r.Done {
			// Prepend a space in case the earlier code ends
			// with '/', which would give us a "//" comment.
			repl := " " + gofmtPos(expr, old.Pos())
			end := fset.Position(old.End())
			// Subtract 1 from the column if we are going to
			// append a close parenthesis. That will set the