Bug 4958 – Floating point enums should check for total loss of precision

This is a minor issue, but it has worried me ever since floating-point enums were introduced. This code compiles on 2.049: enum FloatEnum : float { A = float.max/2, B, C } // but this assert fails! static assert(FloatEnum.A != FloatEnum.B); It's an obscure trap, but it's easy to fix. ----------------- PATCH: enum.c, EnumDeclaration::semantic(), line 234. // Now set e to (elast + 1) e = new AddExp(em->loc, elast, new IntegerExp(em->loc, 1, Type::tint32)); e = e->semantic(sce); e = e->castTo(sce, elast->type); e = e->optimize(WANTvalue | WANTinterpret); + // Check that e != elast (not always true for floats) + Expression *etest = new EqualExp(TOKequal, em->loc, e, elast); + etest = etest->semantic(sce); + etest = etest->optimize(WANTvalue | WANTinterpret); + if (etest->toInteger()) + error("enum member %s has inexact value, due to loss of precision", em->toChars()); } elast = e; em->value = e;

Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/f9c2d24e198c03194af4cc837f7bbb4488972b8e Merge pull request #671 from yebblies/issue4958 Issue 4958 - Floating point enums should check for total loss of precision

2.059 Win32 PS E:\DigitalMars\dmd2\samples> rdmd -w --main bug.d bug.d(3): Error: enum bug.FloatEnum enum member B has inexact value, due to loss of precision bug.d(3): Error: enum bug.FloatEnum enum member C has inexact value, due to loss of precision PS E:\DigitalMars\dmd2\samples>