in src/transformer_util.ts [172:180]
export function isTypeNodeKind(kind: ts.SyntaxKind) {
return (kind >= ts.SyntaxKind.FirstTypeNode && kind <= ts.SyntaxKind.LastTypeNode) ||
kind === ts.SyntaxKind.AnyKeyword || kind === ts.SyntaxKind.NumberKeyword ||
kind === ts.SyntaxKind.ObjectKeyword || kind === ts.SyntaxKind.BooleanKeyword ||
kind === ts.SyntaxKind.StringKeyword || kind === ts.SyntaxKind.SymbolKeyword ||
kind === ts.SyntaxKind.ThisKeyword || kind === ts.SyntaxKind.VoidKeyword ||
kind === ts.SyntaxKind.UndefinedKeyword || kind === ts.SyntaxKind.NullKeyword ||
kind === ts.SyntaxKind.NeverKeyword || kind === ts.SyntaxKind.ExpressionWithTypeArguments;
}