Bug 17743 – Type system hole: escaping inout delegates

DMD v.2075.0: @safe: int a; immutable(int) b=2; inout(int)* delegate(inout(int)*) dg; inout(int)* prepare(inout(int)* x){ dg = y=>x; return x; } void main(){ prepare(&b); int* y=dg(&a); assert(&b is y); // passes. ouch. *y=3; assert(b is *&b); // fails! }

This is why inout data is not allowed to be stored as a global (which essentially you have done). Basically, inout data should not be allowed to escape the function except via the parameters or return, where it is properly handled.

As I understand, it's due to decision that nested functions use inout qialifier of the outer function. Then an easy way to fix this is to disallow conversion of such nested function to inout-typed delegate.

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