https://d.puremagic.com/issues/show_bug.cgi?id=11934
Summary: Allow `ref` in `foreach` over range iff `front`
returns by `ref`
Product: D
Version: D2
Platform: All
OS/Version: All
Status: NEW
Keywords: accepts-invalid
Severity: normal
Priority: P2
Component: DMD
AssignedTo: [email protected]
ReportedBy: [email protected]
--- Comment #0 from Denis Shelomovskij <[email protected]> 2014-01-16
11:45:17 MSK ---
Test code:
---
struct S1
{
@property bool empty();
@property int front();
void popFront();
}
struct S2
{
@property bool empty();
@property ref int front();
void popFront();
}
void main()
{
static assert( __traits(compiles, { foreach( n; S1()) { } }));
static assert(!__traits(compiles, { foreach(ref n; S1()) { } })); // fails
static assert( __traits(compiles, { foreach(ref n; S2()) { } }));
}
---
When `front` doesn't return by `ref` it means returned value is a temporary and
its modification is nonsense. In such case `ref` in `foreach` should be
rejected.
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