Diagnostic codes: must-not-exist: A file is in the `files` of a `mustNotExist` rule, such as a file in no part or in a reserved folder. # must-not-exist > A file is in the `files` of a `mustNotExist` rule, such as a file in no part or in a reserved folder. Rule violations. This text is what `archangel docs must-not-exist` prints. A file is in the `files` of a `mustNotExist` rule, such as a file in no part or in a reserved folder. ## Example ```ts // rule({ files: { all: ['src/**', { not: { element: '*' } }] }, mustNotExist: true }) // src/stray.ts, which no element's pattern matches ``` With `folders` instead of `files`, the rule gives one violation for each folder it covers, not one for each file in it: ```ts rule({ folders: 'src/processes', mustNotExist: true }) ``` ## What to do Move the file to where the architecture puts it, or delete it. The `files` or `folders` of a `mustNotExist` rule may match nothing, because that is how the rule passes.