To give a reference to OneOfOne’s answer, see the Conversions section of the spec. It states that A non-constant value x can be converted to type T in any of these cases: x is assignable to T. x‘s type and T have identical underlying types. x‘s type and T are unnamed pointer types and their … Read more
You can use == to compare with a zero value composite literal because all fields in Session are comparable: if (Session{}) == session { fmt.Println(“is zero value”) } playground example Because of a parsing ambiguity, parentheses are required around the composite literal in the if condition. The use of == above applies to structs where … Read more
The mutability attribute is marked on a storage (constant or variable), not a type. You can think struct has two modes: mutable and immutable. If you assign a struct value to an immutable storage (we call it let or constant in Swift) the value becomes immutable mode, and you cannot change any state in the … Read more
It is not possible to create cyclic structures with borrowed pointers. There is not any good way of achieving cyclic data structures at present; the only real solutions are: Use reference counting with Rc<T> with a cyclic structure with Rc::new and Rc:downgrade. Read the rc module documentation and be careful to not create cyclic structures … Read more
Lifetime ‘a in fn foo(&’a self, …) … is defined for impl<‘a>, that is it is the same for all foo calls. Lifetime ‘a in fn get_mut<‘a>(&’a mut self) … is defined for the function. Different calls of get_mut can have different values for ‘a. Your code impl<‘a> Foo<‘a> { fn foo(&’a self, path: &str) … Read more
is there a way to do it without extracting their “inner” values every time with pattern matching, and without implementing the Add, Sub, … traits and overloading operators? No, the only way is to implement the traits manually. Rust doesn’t have an equivalent to the Haskell’s GHC extension GeneralizedNewtypeDeriving which allows deriving on wrapper types … Read more
The assignability rules are forgiving for anonymous types which leads to another possibility where you can retain the original definition of A while allowing short composite literals of that type to be written. If you really insist on an anonymous type for the B field, I would probably write something like: package main import “fmt” … Read more