https://issues.dlang.org/show_bug.cgi?id=18807
Issue ID: 18807 Summary: RefRange behaves very differently for Input Ranges and Forward Ranges Product: D Version: D2 Hardware: All URL: http://dlang.org/ OS: All Status: NEW Severity: major Priority: P3 Component: phobos Assignee: nob...@puremagic.com Reporter: e...@weka.io Example program: import std.range: refRange, iota; struct R1 { auto r = iota(3); alias r this; } void works() { R1 r1; foreach(x; refRange(&r1)) {} assert(r1.empty); } struct R2 { auto r = iota(3); alias r this; @property auto save() { return this; } } void explodes() { R2 r2; import std.range; foreach(x; refRange(&r2)) {} assert(r2.empty); // <-- BOOM } works() is fine. explodes() fails on the assertion. The only difference is that R2 defines save(). What happens is that the foreach calls opSlice (if it exists), which calls save. opSlice exists iff save exists. Upgrading an existing input range to a forward range invisibly breaks any code that used foreach on a refRange of that range. --