Bug 2448 – template return by reference causes seg fault

import std.stdio; ref T iif(T)(bool condition, ref T lhs, ref T rhs) { if ( condition ) return lhs; return rhs; } ref int int_iif(bool condition, ref int lhs, ref int rhs) { if ( condition ) return lhs; return rhs; } void main() { int a = 10, b = 11; int_iif(a<b, a, b) = 42; writeln("a = ", a, " and b = ", b); // a = 42 and b = 11 iif(a<b, a, b) = 52; // seg fault writeln("a = ", a, " and b = ", b); }

Adding another example and bumping this to major because it stops std.algorithm development dead in its tracks. template ElementType(R) { alias typeof({ R r; return r[0]; }()) ElementType; } bool empty(T)(in T[] a) { return !a.length; } void next(T)(ref T[] a) { assert(a.length); a = a[1 .. $]; } void retreat(T)(ref T[] a) { assert(a.length); a = a[0 .. $ - 1]; } T head(T)(T[] a) { assert(a.length); return a[0]; } ref T toe(T)(T[] a) { assert(a.length); return a[a.length - 1]; } struct Retro(R) { private: R _input; public: bool empty() { return _input.empty; } void next() { _input.retreat; } ElementType!(R) head() { return _input.toe; } } void main() { void test(int[] input) { foreach (e; Retro!(int[])(input)) { } } test([ 1 ]); }

Fixed dmd 2.025