Bug 6934 – [CTFE] can't use $ in a slice of an array passed by ref
Status
RESOLVED
Resolution
FIXED
Severity
normal
Priority
P2
Component
dmd
Product
D
Version
D2
Platform
x86
OS
Windows
Creation time
2011-11-11T19:41:00Z
Last change time
2015-06-09T05:11:43Z
Keywords
rejects-valid
Assigned to
nobody
Creator
bearophile_hugs
Comments
Comment #0 by bearophile_hugs — 2011-11-11T19:41:18Z
It seems transversal() can't run at compile-time:
import std.range: transversal;
int foo() {
auto M = [[1,2], [3,4]];
foreach (x; transversal(M, 0)) {}
return 0;
}
enum _ = foo();
void main() {}
DMD 2.057head gives:
...\dmd2\src\phobos\std\array.d(328): Error: Cannot determine length of Transversal([[1,2],[3,4]],0u)._input at compile time
...\dmd2\src\phobos\std\range.d(4648): called from here: popFront(this._input)
test.d(4): called from here: __r1.popFront()
test.d(7): called from here: foo()
Comment #1 by clugdbug — 2011-11-19T00:03:47Z
Reduced test case:
------
struct Struct6934 {
int[] x = [1,2];
}
void bar6934(ref int[] p) {
p = p[1..$];
}
int bug6934() {
Struct6934 q;
bar6934(q.x);
return 1;
}
static assert(bug6934());
Comment #2 by clugdbug — 2011-11-19T12:24:51Z
In fact passing arrays by reference is broken in non-trivial cases.
Changing the test case to include an index or slice assignment reveals wrong-code problems:
void bar6934(ref int[] p) {
p[0] = 12;
assert(p[0] == 12); // fails!!!
p[0..1] = 17;
assert(p[0] == 17); // fails!!!
p = p[1..$];
}
This applies to any complicated passing of an array by ref (any dotvar or index expression, or combination thereof).
It applies to array index assignment, and slice assignment.