in lib/role.ts [271:278]
public addToPrincipalPolicy(statement: PolicyStatement): AddToPrincipalPolicyResult {
if (!this.defaultPolicy) {
this.defaultPolicy = new Policy(this, 'DefaultPolicy');
this.attachInlinePolicy(this.defaultPolicy);
}
this.defaultPolicy.addStatements(statement);
return { statementAdded: true, policyDependable: this.defaultPolicy };
}