Bug 2701 – Can't declare struct, assign lvalue via opAssign in same statement

struct Bar { uint num; Bar opAssign(uint otherNum) { num = otherNum; return this; } } void main() { uint foo = 1; Bar bar = foo; // Error: e2ir: cannot cast from uint to Bar. Bar bar2; bar2 = foo; // Works. } Not sure if this is actually a valid bug, since the spec states that "The assignment operator cannot be overloaded for rvalues that can be implicitly cast to the lvalue type." However, if the previous sentence does implicitly disallow this from working, it should be stated more clearly, instead of in a single sentence of language legalese.

You can't use opAssign for initialisation; you have to use opCall. Specifically, Bar bar = foo; is rewritten as: Bar bar = Bar(foo); which is further rewritten as: Bar bar = Bar.opCall(foo); I'm not sure if this is documented explicitly anywhere; I just remember this from when it was implemented.

I'm closing this, since this appears to be what C'tors are for. The following example demonstrates. Perhaps this should be better documented, though. struct Bar { uint num; this(uint otherNum) { opAssign(otherNum); } Bar opAssign(uint otherNum) { num = otherNum; return this; } } void main() { int foo = 1; Bar bar = foo; // Error: e2ir: cannot cast from uint to Bar. Bar bar2; bar2 = foo; // Works. }