Function assert

Defines a TokenParser or SymbolParser that will execute parser and pass it's result to assertion.

• If parser returns with an error, the error is propagated without executing the assertion
• If assertion evaluates to some Identifiable object, that object will be returned as the error of the assertion.
• If assertion evaluates to null, then the assertion is considered successful and the result of parser is propagated.

It can be used to attach assertion operations in a parser result and determine if a token satisfies specific criteria at that lexical scope.

Returns

A new TokenParser or SymbolParser that will execute parser and attach assertion operations defined by assertion.