https://issues.dlang.org/show_bug.cgi?id=20009
Issue ID: 20009
Summary: isForwardRange doesn't work with alias range this or
inheritance
Product: D
Version: D2
Hardware: x86
OS: Mac OS X
Status: NEW
Severity: enhancement
Priority: P1
Component: phobos
Assignee: [email protected]
Reporter: [email protected]
struct FR {
bool empty = true;
void popFront() {}
auto front() { return 0; }
FR save() { return this; }
}
struct S {
FR range;
alias range this;
}
pragma(msg, isInputRange!S); // true
pragma(msg, isForwardRange!S); // false
It's because isForwardRange is defined as:
isInputRange!R && is(ReturnType!((R r) => r.save) == R);
But it should be:
isInputRange!R && is(R : ReturnType!((R r) => r.save));
The same thing will happen if you try an inherit from an interface that is a
forward range, and if the save function returns the base class it will fail.
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