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dead_code_analyzer

Table of contents

Introduction

The dead_code_analyzer's main goal is to help developers maintain their OCaml codebase by identifying globally unused elements of code. Such elements can then be dropped, either from the interface or from the implementation, depending on the context. It is a static analyzer and an addition to the compiler's already existing warnings.

An element of code is considered unused if there is no explicit use of it. This means that it should be removable from the codebase without changing the semantics of the program nor breaking compilation1. This "unused" property is not considered transitively2. It implies that each reported element can be taken care of independently. It also implies that removing an element reported may lead to the detection of new unused elements.

The unused elements tracked are:

  • Exported values
  • Methods
  • Constructors and record fields

In addition to those unused elements, the dead_code_analyzer also tracks the use of optional arguments. More specifically, it focuses on those:

  • Always used
  • Never used (or only to be discarded with None)

Finally, as a bonus, it also identifies some stylistic issues. Although this is not related to the use of elements of code.

Topics

This documentation is split accross different topics:

  • Usage describes the usage of the dead_code_analyzer and its options.
  • Exported Values describes the semantics and usage of the "unused exported values" report section, and provides examples.

Footnotes

Footnotes

  1. Actually, the compilation may break in some cases. E.g. removing a constructor from a variant type would trigger compilation errors on patterns matching that constructor. ↩

  2. Elements of code used by an unused element of code are still considered used. Consequently, an element only used by unused elements is still considered used. It would only be reported as unused after all its users have been removed from the codebase.
    E.g. A function f called by another function g is always considered used, no matter the status of g. ↩