dialyzer

Dialyzer is a static analysis tool designed for the Erlang programming language and the broader BEAM ecosystem. It analyzes code without executing it to detect potential type errors, contract violations, and other inconsistencies. Dialyzer aims to improve reliability by identifying issues early in the development process and guiding developers toward more robust specifications.

The tool works by performing abstract interpretation over the code base. It relies on optional type specifications provided in Erlang source, such as -spec and -type annotations, to refine its analysis and produce what are called success typings. Dialyzer can also infer types to some extent when specs are incomplete. It examines function calls, pattern matching, guards, and data flows to identify mismatches, unreachable code, and other risky constructs. The analysis is typically modular, reusing results via a persistent look-up table (PLT) to speed up checks across many modules.

Usage and output commonly involve running Dialyzer on a set of files or modules, often with a prebuilt PLT. Results include warnings about possible type errors, calls to undefined or non-exported functions, mismatches between function specifications and actual call sites, and dead or unreachable code. While powerful, the tool may emit false positives in some situations and should be used in conjunction with explicit specifications and testing.

Dialyzer has become a standard part of Erlang projects and is also used in the Elixir ecosystem through integrations that connect Elixir specifications with the Erlang analysis engine. It emphasizes static reasoning about code quality and type correctness without introducing runtime overhead.