Bug 21538 – Overriding with more attributes on delegate parameter is allowed

interface I { void f(const void delegate() dg) const @safe; } class C : I { // this overrride should not be legal override void f(const void delegate() @safe dg) const @safe { } } void main() @safe { const void delegate() @system dg = { }; C c = new C; // c.f(dg); // error, expected (cast(I) c).f(dg); // no error }

DMD rejected the override from version 2.066 to 2.074.1; the regression affects DMD since 2.075.1. Just to prove that the cast and the actual delegate isn't the issue, the following compiles, too: auto dg = delegate() @system { int* p; int x; p = &x; }; // unsafe actions I i = new C; i.f(dg); // okay, unexpeced It works with function pointers, too: auto fp = () @system { int* p; int x; p = &x; }; i.g(fp);

From spec [1]: "A function in a derived class with the same name and covariant with a function in a base class overrides that function". Also, [2] (point 8) defines covariance: "A covariant function has a type that is implicitly convertible to the type of the overridden function.". Finally, [3] (point 6) shows that @safe functions are covariant with @system functions. PR that explicitly introduced this: https://github.com/dlang/dmd/pull/6731 . I think that this case was simply overlooked. Functions that implement interface functions should match exactly. [1] https://dlang.org/spec/function.html#function-inheritance [2] https://dlang.org/spec/function.html#virtual-functions [3] https://dlang.org/spec/function.html#safe-functions

@RazvanN7 created dlang/dmd pull request #12160 "Fix Issue 21538 - Overriding with more attributes on delegate parameter is allowed" fixing this issue: - Fix Issue 21538 - Overriding with more attributes on delegate parameter is allowed https://github.com/dlang/dmd/pull/12160

*** Issue 21602 has been marked as a duplicate of this issue. ***

*** Issue 20409 has been marked as a duplicate of this issue. ***

@MoonlightSentinel created dlang/dmd pull request #13267 "Fix 21538,20904: Correct implicitConvTo order for delegate parameters in `Type.covariant`" fixing this issue: - Fix 21538,20904: Correct implicitConvTo order for delegate parameters... ... in `Type.covariant` The ordering was inversed when compared to function pointers. That caused the check to accept e.g. less restrictive attributes for callbacks. Also changed the equality checks for `TypeFuntion` and `TypeDelegate` to `equals` because `==` didn't call the former and hence caused problems for duplicate instances. https://github.com/dlang/dmd/pull/13267

dlang/dmd pull request #13267 "Fix 21538,20904: Correct implicitConvTo order for delegate parameters in `Type.covariant`" was merged into master: - f81a1ccaeb0aa3d5575332ceeca4280b5c585d7d by MoonlightSentinel: Fix 21538,20904: Correct implicitConvTo order for delegate parameters... ... in `Type.covariant` The ordering was inversed when compared to function pointers. That caused the check to accept e.g. less restrictive attributes for callbacks. Also changed the equality checks for `TypeFuntion` and `TypeDelegate` to `equals` because `==` didn't call the former and hence caused problems for duplicate instances. https://github.com/dlang/dmd/pull/13267