On 5/2/16 3:13 AM, Iain Buclaw wrote:
Here's a small puzzle, in which there are both a simple and cryptic
combined. To make it easier, I've added a some multiple choice answers
at the bottom.
Winner of the simple puzzle gets a free beer from me at dconf.
Winner of the cryptic puzzle gets a free meal.
Q: What is the explanation for this error when building std.bigint?
---
$ aarch64-linux-gnu-gdc -o std/bigint.o -Wall -Werror -g -frelease -O2
-nostdinc -pipe -Wno-deprecated -c std/bigint.d
std/uni.d:2627:50: error: template std.algorithm.searching.countUntil
cannot deduce function from argument types !("a[0] >
0x80")(CodepointInterval[]), candidates are:
std/algorithm/searching.d:684:11: note:
std.algorithm.searching.countUntil(alias pred = "a == b", R, Rs...)(R
haystack, Rs needles) if (isForwardRange!R && Rs.length > 0 &&
isForwardRange!(Rs[0]) == isInputRange!(Rs[0]) &&
is(typeof(startsWith!pred(haystack, needles[0]))) && (Rs.length == 1 ||
is(typeof(countUntil!pred(haystack, needles[1..__dollar])))))
std/algorithm/searching.d:772:11: note:
std.algorithm.searching.countUntil(alias pred = "a == b", R, N)(R
haystack, N needle) if (isInputRange!R &&
is(typeof(binaryFun!pred(haystack.front, needle)) : bool))
std/algorithm/searching.d:841:11: note:
std.algorithm.searching.countUntil(alias pred, R)(R haystack) if
(isInputRange!R && is(typeof(unaryFun!pred(haystack.front)) : bool))
std/uni.d:1853:29: error: template instance
std.uni.InversionList!(GcPolicy) error instantiating
---
A:
---
[1]: Template deduction/matching failed to find a suitable candidate for
countUntil.
This answer is trivially true. It even says so in the error message :)
What I assume you mean is that one *should* match but there is a bug in
the matching mechanism? I'd say no -- this would be too easy an answer
[2]: The ptrdiff_t and size_t types have a different size.
Wow, it would be a copy-paste error of some sort? An interesting
possibility. But I'm going to say no, I don't see how this comes into
play for the template constraints.
[3]: An untested version path had a semantic error.
This is a possibility, but not very likely (in terms of errors that are
prone to occur).
[4]: An untested template instantiation had a missing member.
This has my vote. I've had this bite me many times...
[5]: The template function core.varargs.va_arg does not exist.
haha!
[6]: A static assert was triggered in std.math.
No, but again possible. If this is the problem, it comes down to the
issues with is(typeof(some code)) that have been discussed lately.
[7]: The std.format module does not support 128-bit reals.
I'd say no, because I don't see how it relates to the error messages.
[8]: The compiler didn't add a predefined version for little/big endian.
ugh. How are we to guess at your environment? ;) I'd say no.
[9]: The order that modules are imported on AArch64 unearthed a bug in
the semantic pass.
Possible. Still going with 4.
-Steve
