Bug 10586 – DMD unable to interpret cascaded template calls at compile time

I am using latest github dmd -- 712c3e256b1198523bb8a5c49e5e08d3f8409855 Here is the minimized code for the regression. $ dmd -c bvec.d foo.d(12): Error: Cannot interpret FooSize!N at compile time foo.d(13): while evaluating SIZE.init foo.d(13): while looking for match for FooParams!(1LU) foo.d(9): Error: template instance foo.foo!1 error instantiating I think the regression got introduced while fixing 10579. // Regression Code starts here private template FooParams(size_t SIZE) { private alias ubyte StoreT; } template FooSize(size_t N=1) { enum size_t FooSize = N; } enum foo!1 BIT_0 = foo!1.init; struct foo(size_t N) { enum size_t SIZE = FooSize!N; private alias FooParams!(SIZE).StoreT store_t; }

(In reply to comment #0) > I think the regression got introduced while fixing 10579. No, that's unrelated. This isn't a CTFE bug, it's a bug in enums. Semantic has not yet been run on the enum initializer. My guess is that this is a forward reference issue. If you change it: struct foo(size_t N) { - enum size_t SIZE = FooSize!N; + enum size_t SIZE = 0 + FooSize!N; then you get a segfault, because the type is still NULL. My guess is that this was exposed by my "do const-folding in CTFE" patch. Previously these kinds of errors went undetected.

Further reduced shows I'm wrong about it being enums: ------------ template FooParams(size_t K) { alias int X; } struct foo { static const int SIZE = int.sizeof; alias FooParams!(SIZE).X Y; } ----------- bug.d(6): Error: Cannot interpret int at compile time bug.d(7): while evaluating SIZE.init bug.d(7): while looking for match for FooParams!(4) --- A very difficult related case is this one: const int Z = baz(3); const int W = baz(2); int baz(int k) { if (k == 3) return W; return 6; } static assert(Z == 6); because it means that baz cannot be JIT-compiled. Arguably this is a circular reference. It would be much simpler and would give better performance if we disallowed pseudo-circular refs.

The same regression was reported in 10669, and it was already fixed by Rainer Schuetze in git-head. *** This issue has been marked as a duplicate of issue 10669 ***