Rust Types and APIs

Use this when the real question is how much of the design should be expressed in types, traits, and public signatures.

Working stance

• Make invalid states hard to represent before adding runtime checks.
• Keep public APIs narrower than internal helper code.
• Prefer concrete types until abstraction pressure is real.
• Use trait objects for extension seams and heterogeneity, not by reflex.
• Prefer typed domains and borrowed read-only inputs over stringly or collection-specific signatures.
• Accept broad inputs; return precise outputs.

Decision surface