zsh PATH variable not properly set from another environment variable

Question

I want to set my path (and some other environment variables) based on a certain directory, so I have the following file in my home directory

export MY_DIR="/path/to/dir"
export PATH=$MY_DIR/bin:$PATH
export MY_OTHER_VAR="$MY_DIR/folder"

I source that in my ~/.zshrc with the following line: [[ -e ~/my_file.sh ]] && emulate sh -c ' source ~/my_file.sh

However, when I log in, $MY_DIR/bin is not in my path. If I echo $PATH, I get %F{51}~%f where $MY_DIR/bin should be. However, both MY_DIR and MY_OTHER_VAR were set correctly.

Have I done something wrong, or is this some weird bug in zsh (it seems to work as expected with bash)?

Edit

I have used both source and ~ elsewhere in my zshrc without issue. However, I tried moving the file to /etc/zsh/my_file.sh and sourcing it from etc/zsh/zprofile. I also tried using . rather than source, but even with those changes, I still see the same %F{51}~%f in my path variable. Actually, I've noticed that I see whatever my current directory is in the PATH variable, so for example, if I navigate to /etc/zsh/ and echo $PATH, I see %F{51}/etc/zsh%f.

Full code to reproduce:

/etc/zsh/zprofile:

[[ -e /etc/zsh/my_file.sh ]] && emulate sh -c ' . /etc/zsh/my_file.sh'

/etc/zsh/my_file.sh:

export MY_DIR="/home/matt/code"
export PATH="$MY_DIR/bin:$PATH"
export MY_PYTHON="$MY_DIR/python"

EDIT 2

So I am using a custom prompt which prints my current path in cyan. If I disable that prompt, my PATH variable gets set properly. In the script for the prompt, I use a variable that I call path (lowercase). Apparently, while bash doesn't confuse it with PATH, zsh does. Thanks to all for the help.

Answer 1

My issue was actually not in the code where I was attempting to set the path to "$MY_DIR/bin:$PATH", but in a different script that I was sourcing in my .zshrc. I'm using a custom script to set my shell prompt in which I used a variable declared as path, thinking that would not conflict with the environment variable PATH, but, as pointed out by @Adaephon in the comments, zsh bidirectionally synchronizes the path keyword with PATH.

Thus, for me, the solution was to rename the variable in my prompt function to cur_path (or similar). Attempting to define the variable as local path will result in a segfault.