[Issue 24208] [DIP1000] Scope pointer can escape via non-scope parameter of pure nested function

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24208

Paul Backus <snarwin+bugzilla at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[DIP1000] Nested function   |[DIP1000] Scope pointer can
                   |can pass scope pointer to   |escape via non-scope
                   |non-scope parameter         |parameter of pure nested
                   |                            |function

--- Comment #4 from Paul Backus <snarwin+bugzilla at gmail.com> ---
The bug is caused by an undocumented special-case language rule that allows
scope pointers to be assigned to non-scope parameters of pure functions in some
cases. This special case is implemented in the DMD frontend by the function
TypeFunction.parameterStorageClass.

In comment #1's example, `escape` is inferred to be weakly pure. As a result,
TypeFunction.parameterStorageClass allows the parameter `p` to accept a scope
pointer as an argument, and the error that would normally be issued by
checkParamArgumentEscape is suppressed.

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