CONVENTION.md

Code conventions

Use of auto

The auto keyword shall only be used, if the deduced type is obvious or specifying the type is unreasonably complicated. Specifically that means it may only be used in range-based for loop, or in a variable declaration when the initializer is an allocation using new, an initialisation or is cast. Additionally, if the deduced type would be a pointer, this should be specified by using auto *. The only exception to this rule is when destructuring a type;

Example

// Literals
auto a = 4; // BAD
auto b = "string"; // BAD
auto c = 4.2; // BAD

// User types
auto d = Class(); // Good
auto e = new Class(); // BAD
auto *f = new Class(); // Good
auto g = expression; // BAD
auto *h = expression; // BAD
auto [i, j] = destructurable; // Good

// Casts
auto k = (Class) expression; // Good
auto l = expression.to_class(); // BAD

// range-based for loops
for (auto elem : value_range) {} // Good
for (auto elem : ptr_range) {} // Bad
for (auto *elem : ptr_range) {} // Good
for (auto [key, val] : destructurable_range) {} // Good