modernize-use-nodiscard

Adds [[nodiscard]] attributes (introduced in C++17) to member functions in order to highlight at compile time which return values should not be ignored.

Member functions need to satisfy the following conditions to be considered by this check:

• no [[nodiscard]], [[noreturn]], __attribute__((warn_unused_result)), [[clang::warn_unused_result]] nor [[gcc::warn_unused_result]] attribute,
• non-void return type,
• non-template return types,
• const member function,
• non-variadic functions,
• no non-const reference parameters,
• no pointer parameters,
• no template parameters,
• no template function parameters,
• not be a member of a class with mutable member variables,
• no Lambdas,
• no conversion functions.

Such functions have no means of altering any state or passing values other than via the return type. Unless the member functions are altering state via some external call (e.g. I/O).

Example

bool empty() const;
bool empty(int i) const;

transforms to:

[[nodiscard] bool empty() const;
[[nodiscard] bool empty(int i) const;

Options

Example

bool empty() const;
bool empty(int i) const;

transforms to:

NO_DISCARD bool empty() const;
NO_DISCARD bool empty(int i) const;

if the :option:`ReplacementString` option is set to NO_DISCARD.