Re: What is the state of scope function parameter?

[via Digitalmars-d-learn]

On Wednesday, 29 March 2017 at 05:15:33 UTC, Ali Çehreli wrote:
(More correctly, "scope storage class".)
  https://dlang.org/spec/function.html#Parameter

still says

  scope: references in the parameter cannot be escaped
         (e.g. assigned to a global variable). Ignored for
         parameters with no references

However, it doesn't behave that way. For example, my example 
here currently is a lie because there is no compilation error 
with 2.073.2:


http://ddili.org/ders/d.en/function_parameters.html#ix_function_parameters.scope

What's the truth? How would you change the text there?

Thank you,
Ali

The truth is that almost non of the scope checks are on, unless 
you compile with -dip1000:
$ source ~/dlang/dmd-2.073.2/activate
$ dmd ddili_scope_test1.d
$ echo $?
0
$ dmd -dip1000 ddili_scope_test1.d
ddili_scope_test1.d(5): Error: scope variable parameter may not 
be returned

Now that's one error, out of two expected, so what's going on 
here? As DIP1000 mentions 
(https://github.com/dlang/DIPs/blob/master/DIPs/DIP1000.md#safe):

Errors for scope violations are only reported in @safe code.

So if when I changed the code to:

int[] globalSlice;

int[] foo(scope int[] parameter) @safe {
    globalSlice = parameter;    // ← compilation ERROR
    return parameter;           // ← compilation ERROR
}

void main() {
    int[] slice = [ 10, 20 ];
    int[] result = foo(slice);
}

I got:
$ dmd -dip1000 ddili_scope_test1.d
ddili_scope_test1.d(4): Error: scope variable parameter assigned 
to non-scope globalSlice
ddili_scope_test1.d(5): Error: scope variable parameter may not 
be returned

Just as expected.