[Issue 24211] New: Const nested function can mutate context

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24211

          Issue ID: 24211
           Summary: Const nested function can mutate context
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: snarwin+bugzilla at gmail.com

As of DMD 2.105.2, the following program compiles:

---
void main()
{
    int n;
    void fun() const { n = 123; }
}
---

Despite being a const function, `fun` is allowed to mutate its context.

If fun is made immutable instead of const, the program does not compile.

Possibly a duplicate of issue 16248 or issue 18566.

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