Bug 22225 – SumType: Some assignments should be able to execute in safe code

In general, assigning to a SumType that may contain a pointer or reference must be @system, because it could overwrite a pointer or reference that @safe code has access to, leading to undefined behavior: --- int n; int example() @safe { SumType!(int*, int) x = &n; return x.match!( (int n) => n, (ref int* p) { x = 123456789; // overwrites p (currently @system) return *p; // kaboom } ); } --- However, in the special case where only one member of the SumType contains pointers or references, such an assignment could be @safe, because (a) overwriting a non-pointer with a pointer is @safe, and (b) overwriting a pointer with another pointer of the same type is @safe. Example: --- void main() @safe { alias SM = SumType!(string, int); auto sm = SM(123); sm = SM("this should be @safe"); } --- See also: https://github.com/pbackus/sumtype/issues/67

@pbackus created dlang/phobos pull request #8201 "Fix Issue 22225 - SumType: Some assignments should be able to execute…" fixing this issue: - Fix Issue 22225 - SumType: Some assignments should be able to execute in safe code https://github.com/dlang/phobos/pull/8201

dlang/phobos pull request #8201 "Fix Issue 22225 - SumType: Some assignments should be able to execute…" was merged into master: - 895edd4260bd953fa1420cda06746287b7abb5eb by Paul Backus: Fix Issue 22225 - SumType: Some assignments should be able to execute in safe code https://github.com/dlang/phobos/pull/8201