Design Parsing Boundaries for Interdependent Message Types

A protocol-buffer-related parsing task includes dependencies on newly defined message types. Explain which input and output details you would clarify, and how you would separate parsing from type resolution so definitions can refer to one another. ### Constraints & Assumptions The source names parsing a protobuf with dependencies on new definitions, but supplies no grammar, encoded payload, or expected output. This is a bounded engineering discussion of those disclosed dependencies, not a claimed implementation of the full Protocol Buffers specification. ### Clarifying Questions Is the input a schema definition, encoded message bytes, or a set of generated descriptors? What must the parser return? Can types be referenced before their definition, imported, nested, or recursive? Which syntax and validation rules are in scope? ### What a Strong Answer Covers Explicit format boundaries, a structured intermediate representation, symbol/type resolution, useful errors, and appropriate handling of dependencies and recursion. ### Follow-up Questions Why can a one-pass “type must already exist” lookup reject a valid forward reference? When is a cycle a legitimate recursive type rather than an error? What additional information is needed to parse encoded values safely?