CMake linking error with multilevel src directory - cmake

Question

I'm having issues linking my project together using cmake.
The project consists of a library, "mylib", and an executable, "mybin", which is linked with it. The structure is the following:
.
├── CMakeLists.txt
├── include
│ ├── mylib.h
│ ├── entities
│ │ ├── entities.h
│ │ ├── entityA.h
│ │ └── entityB.h
│ └── shapes
│ ├── shapes.h
│ ├── shapeA.h
│ └── entityB.h
└── src
├── main.cpp
├── entities
│ ├── entityA.cpp
│ └── entityB.cpp
└── shapes
├── shapeA.cpp
└── entityB.cpp
Where mylib uses all .cpp and .h files (except from main.cpp) to create a static library, and mybin uses main.cpp and links with mylib.h. mylib.h pulls the other header files from the include directory.
Right now, my CMakeLists.txt looks like this:
cmake_minimum_required(VERSION 3.13)
project(myproject VERSION 1.1.0 LANGUAGES C CXX)
add_library(mylib
src/entities/entityA.cpp
src/entities/entityB.cpp
src/shapes/shapeA.cpp
src/shapes/shapeB.cpp
include/mylib.h
include/entities/entities.h
include/entities/entitiesA.h
include/entities/entitiesB.h
include/shapes/shapes.h
include/shapes/shapeA.h
include/shapes/shapeB.h
)
target_include_directories(mylib PUBLIC include)
target_link_libraries(mylib PUBLIC)
target_compile_features(mylib PRIVATE cxx_std_11)
add_executable(mybin src/main.cpp)
target_link_libraries(mybin PRIVATE mylib)
target_compile_features(mybin PRIVATE cxx_std_11)
When I try to build my code, with
mkdir build
cd build
cmake ..
make
The library builds fine, but I get linking errors while the executable is building:
/usr/bin/ld: shapeA.cpp:(.text+0x344): undefined reference to `MyLib::Entities::EntityA::normalize_inplace()'
Not sure how to fix this, I tried to follow numeral tutorials and looking at other issues here and examples, but couldn't get to fix it. The actual code is in my github, in the "cmake" branch.
Thank you very much.
EDIT
The linking error I copied above is used in the src/shapes/shapeA.cpp file:
#include "shapes/shapeA.h"
#include <algorithm>
using MyLib::Entities::EntityA;
Mylib::Shapes::ShapeA::ShapeA() {}
Mylib::Shapes::ShapeA::~ShapeA(){}
bool Mylib::Shapes::ShapeA::intersect(const EntityA &entity) const {
const EntityA invdir = (EntityA(1.0, 1.0, 1.0) + entity).normalize_inplace();
return true;
}
It is defined in src/entities/entityA.cpp :
#include "entities/EntityA.h"
using MyLib::Entities::EntityA;
EntityA::EntityA(double a, double b, double c) :
a_(a), b_(b), c_(c) {}
EntityA::~EntityA(){}
EntityA EntityA::normalize_inplace(){
const double tot = std::sqrt(a_*a_ + b_*b_ + c_*c_);
a_ /= tot;
b_ /= tot;
c_ /= tot;
return EntityA(1.0, 1.0, 1.0);
}
EntityA EntityA::operator+(EntityA other) {
return EntiryA(a_ + other.a_, b_ + other.b_, c_ + other.c_);
}
There are many more linking errors like that one, I think nothing gets linked correctly at all.
Also, I used a makefile previously and all linking was being made correctly.