Reading diagnostics

When Pop rejects source, it reports a diagnostic with a code, message, and source location. Additional labels point to related declarations or expressions, and notes explain constraints that cannot fit in the headline.

Diagnostic code ranges group related work:

Range	Area
POP000x	syntax and source structure
POP100x	names, imports, and visibility
POP200x	types and operations
POP400x	compile-time evaluation and attributes
POP6400–POP6401	documentation XML warnings

Begin with the first diagnostic in source order. A missing end, for example, can make later declarations appear malformed. Fixing the earliest structural problem often removes several follow-on messages.

Errors and warnings

An error prevents the requested compilation stage from succeeding. A warning reports a suspicious or unsafe-to-process construct without necessarily rejecting the program. Documentation XML uses warnings so malformed or unsafe markup can be corrected while its surrounding Pop declaration remains understandable.

Small experiments

When a message is unclear, reduce the program to the smallest file that still produces it. Keep the namespace, the relevant declaration, and one call. Running pop check reduced.pop gives a faster and less noisy feedback loop than repeatedly building a large executable.

Include the Pop version, diagnostic code, reduced source, and exact command when reporting a compiler issue. Diagnostics and accepted syntax can differ between book versions.