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: [email protected]
Reporter: [email protected]
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.
--
