# Specification Notes

There are a few differences between the [Power Query / M Language Specification](https://docs.microsoft.com/en-us/powerquery-m/power-query-m-language-specification), the Power Query implementation, and this implementation.

## Where the Power Query parser differs from the specification

-   An additional match of `primary-expression` is added on the following tokens: `@`, `identifier`, or `left-parenthesis`.
-   The `identifier` construct was changed so that after a period instead of matching `identifier-start-character` it now matches `identifier-part-character`.
-   The `generalized-identifier` construct was changed so that `identifier-start-character` was replaced with `identifier-part-character`. It also accepts quoted identifiers.
-   The try-otherwise is normally transformed internally into a try-catch. Instead we need to preserve the original structure so two additional constructs exist, one for try-catch and the other for try-otherwise.