HashQL Diagnostic Writing

Provides HASH-specific patterns for writing high-quality diagnostics using the hashql-diagnostics crate, ensuring messages are helpful, actionable, and follow consistent style conventions.

Core Principles

Diagnostics should be helpful, not just correct:

✅ DO:

• Start messages with lowercase
• Use backticks for code elements: expected `bool`, found `String`
• Make messages actionable and specific
• Use "invalid" not "illegal"
• Keep help messages as imperatives: "add type annotations"

❌ DON'T: