Remove unnecessary friend keywords

[ZXShady]

Note that I didn't remove it for internal\catch_optional.hpp for friend bool operator==(Optional<T>,Optional<T>) and operator!= since the friend function will allow for implicit conversions which allows comparing against a T like Catch::Optional<int>() == int(1) nor did I make inline functions not inline like operator<< for ITransientExpression.

This change removes several friend declarations that are no longer necessary. Overuse of friend can lead to tighter coupling between classes, reduced encapsulation and thinking it relies on implementation details.
in general avoid granting excessive access unless explicitly required.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.98%. Comparing base (5b3b228) to head (6e6820b).
Report is 1 commits behind head on devel.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #2974      +/-   ##
==========================================
- Coverage   91.01%   90.98%   -0.03%     
==========================================
  Files         198      198              
  Lines        8599     8599              
==========================================
- Hits         7826     7823       -3     
- Misses        773      776       +3     

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[neheb]

../src/catch2/internal/catch_reusable_string_stream.hpp:46:20: error: call to function 'operator<<' that is neither visible in the template definition nor found by argument-dependent lookup
   46 |             *m_oss << value;
      |                    ^
../src/catch2/catch_tostring.hpp:124:21: note: in instantiation of function template specialization 'Catch::ReusableStringStream::operator<<<foo::helper_1403>' requested here
  124 |                 rss.operator<<(value);
      |                     ^
../src/catch2/catch_tostring.hpp:146:88: note: in instantiation of function template specialization 'Catch::StringMaker<foo::helper_1403>::convert<foo::helper_1403>' requested here
  146 |             return ::Catch::StringMaker<std::remove_cv_t<std::remove_reference_t<T>>>::convert(e);
      |                                                                                        ^
../src/catch2/internal/catch_decomposer.hpp:195:42: note: in instantiation of function template specialization 'Catch::Detail::stringify<foo::helper_1403>' requested here
  195 |                     ( os, Catch::Detail::stringify( m_lhs ), m_op, Catch::Detail::stringify( m_rhs ) );
      |                                          ^
../src/catch2/internal/catch_decomposer.hpp:199:19: note: in instantiation of member function 'Catch::BinaryExpr<foo::helper_1403 &, foo::helper_1403 &>::streamReconstructedExpression' requested here
  199 |         constexpr BinaryExpr( bool comparisonResult, LhsT lhs, StringRef op, RhsT rhs )
      |                   ^
../tests/SelfTest/UsageTests/Compilation.tests.cpp:32:22: note: 'operator<<' should be declared prior to the call site or in namespace 'foo'
   32 | static std::ostream& operator<<(std::ostream& out, foo::helper_1403 const&) {
      |                      ^
1 error generated.

[horenmar]

friend declaration in C++ has two reasons

1. To access the internals of a class
2. To declare a hidden friend

While it is annoying that to get 2) you also have to have 1), 2) is desirable enough to keep the functions as hidden friends even if they do not need access to the class internals.

[ZXShady]

friend declaration in C++ has two reasons

1. To access the internals of a class
2. To declare a hidden friend

While it is annoying that to get 2) you also have to have 1), 2) is desirable enough to keep the functions as hidden friends even if they do not need access to the class internals.

Yea,

I guess it can be removed for friended functions declared out of line since hidden friends only work if it is defined inline.

I will update my pr.

[horenmar]

Hidden friends can be defined out of line as well

[ZXShady]

Hidden friends can be defined out of line as well

Oh! I didn't know that, you can close my pr.