Allow in to be Parsed as an Operator

[iamrecursion]

Summary

In Enso's type signature syntax, in behaves more like an operator than a function. However, the parser treats it as a standard variable identifier, which means that it doesn't get interpreted as an operator. This causes problems with how the compiler needs to handle it, as well as problems in how it's parsed relative to other operators (around variable precedence).

Value

The context ascription will be handled properly by the parser.

Specification

• Add the in context ascription operator as an operator in the parser.
• Update the parser to support this new syntax.

Acceptance Criteria & Test Cases

• No parser tests are broken.
• We can correctly parse in as an operator.

[iamrecursion]

Closed. It is hackily supported in the current parser, and will be supported properly in the new parser.