Operations, recursion, and Unknown

Collections and LINQ

Known costs are resolved by Roslyn symbol identity, not by method name text. This prevents an unrelated custom Contains from being treated as List<T>.Contains. Supported mappings distinguish linear list lookup, expected hash lookup, ordering, materialization, deferred pipelines, and terminal enumeration.

Deferred LINQ operators do not pay a full enumeration cost at pipeline creation. Supported terminal operations and foreach consume the pipeline; proven re-enumeration is counted again.

Interprocedural analysis

Safe source calls in the same compilation can be analyzed on demand. Dispatch must be proven safe, and traversal is bounded by call-depth and method budgets. The analyzer does not build an unbounded whole-program call graph.

Direct recursion

Selected direct recurrences can be solved when the recursive call shape and a compatible base case are proven. Supported families include decrement/summation forms, simple exponential recursion, Master Theorem cases, and a restricted Akra–Bazzi subset.

What Unknown means

Unknown means the bounded analysis could not prove a safe estimate. It does not mean O(1), success, failure, or efficient code. Common causes include dynamic or unsafe dispatch, unresolved delegate targets, unsupported loop bounds, mutual recursion, missing base-case evidence, budget exhaustion, cancellation, or unsupported syntax.

The project prefers an explicit inconclusive result to a high-confidence-looking false positive.