Const/mut pointers

[Akuli]

When working with pointers, you can avoid many bugs by marking them as const or mutable. For example, string literals should never be modified, so their type in C is const char *, which means that "hello"[2] = 'x' will fail to compile. (Actually it is a mutable char * pointer for historical reasons, but ideally it would be const char *.)

Jou could do something similar, but I want the syntax to be as obvious as possible. For example, I think it would be good to require a mut or const keyword instead of making one of them the default (Rust's default is const pointer, C's default is mutable).

Some syntax ideas:

# The "obvious" thing for someone coming from other languages
string: byte const* = "Hello"
int_array: int mut* = calloc(10, sizeof int_array[0])
string_array: byte const* mut* = calloc(20, sizeof string_array[0])

# The "obvious" thing for someone new to pointers
string: const* to byte = "Hello"
int_array: mut* to int = calloc(10, sizeof int_array[0])
string_array: mut* to const* to byte = calloc(20, sizeof string_array[0])

[Akuli]

Another idea: Add compiler warnings for common constness mistakes, like trying to mutate a string literal, and keep the syntax as is. I like the simplicity of pointer syntax without constness, and I think it is a good choice for Jou.