Bug 24213 – [DIP1000] Scope pointer can escape via non-scope parameter of pure delegate

As of DMD 2.105.2, the following invalid program compiles and runs without errors: --- alias Dg = void delegate(int* p) @safe pure nothrow; void main() @safe { int* escaped; int n; Dg dg = delegate void (int* p) { escaped = p; }; dg(&n); } --- This program is invalid because, in @safe code, it assigns the address of the variable `n` to the variable `escaped`, which has a longer lifetime than `n`. The expression `dg(&n)` should cause a compile-time error, because it assigns the scope pointer value `&n` to the non-scope parameter `p`. The compiler allows this because, due to the rules laid out in "Inferred scope parameters in pure functions" [1], it believes that the parameter of `dg` cannot escape. However, these rules do not account for the possibility that a pure delegate may escape a non-scope parameter via its nested context. [1]: https://dlang.org/spec/function.html#pure-scope-inference

@pbackus created dlang/dmd pull request #15756 "Fix 24208, 24212, 24213 - `scope` escape via `pure` + nested context" fixing this issue: - Fix issues 24212 and 24213 * Issue 24212 - Scope pointer can escape via non-scope parameter of pure virtual function * Issue 24213 - Scope pointer can escape via non-scope parameter of pure delegate https://github.com/dlang/dmd/pull/15756

dlang/dmd pull request #15756 "Fix 24208, 24212, 24213 - `scope` escape via `pure` + nested context" was merged into master: - a0705285d78430954f0762a078423c13faf874d7 by Paul Backus: Fix issues 24212 and 24213 * Issue 24212 - Scope pointer can escape via non-scope parameter of pure virtual function * Issue 24213 - Scope pointer can escape via non-scope parameter of pure delegate https://github.com/dlang/dmd/pull/15756