Does scope not work on parameters?

[Russ via Digitalmars-d-learn]

Hi, I've been playing around with having classes allocated on the 
stack. I am using the scope keyword for local variables. I 
assumed that the scope modifier for function parameters was 
designed to prevent these from escaping, but the code below 
doesn't show any errors. Is there some newer feature I should be 
using? Thanks.


import std.stdio;

class Foo
{
}

class Bar
{
Foo foo;
}

void doSomething(scope Foo z, Bar b)
{
b.foo = z;
}

void main()
{
Bar b = new Bar;
scope foo = new Foo;
doSomething(foo, b);
}

Re: Does scope not work on parameters?

[Russ via Digitalmars-d-learn]

On Sunday, 23 February 2020 at 03:26:17 UTC, Steven Schveighoffer 
wrote:

On 2/22/20 10:01 PM, Russ wrote:

Is there some newer feature I should be using?


scope escapes are only disallowed in @safe code.

Adding @safe: to the top of this file makes it not compile with 
a complaint:


Error: scope variable z assigned to non-scope b.foo

Which I think is what you expected.

As to why it happens without @safe, you may be managing your 
global variable carefully and ensuring it's unset by the time 
foo goes away. The compiler can't know.


Another reason to enable safe-by-default...

-Steve


Perfect, thank you! I agree that this sort of thing should be on 
by default. Better to opt-out than opt-in for memory safety.