[LLVMbugs] [Bug 22038] New: Members of current instantiation should be non-dependent, but are mostly treated as dependent
bugzilla-daemon at llvm.org
bugzilla-daemon at llvm.org
Sat Dec 27 05:01:05 PST 2014
http://llvm.org/bugs/show_bug.cgi?id=22038
Bug ID: 22038
Summary: Members of current instantiation should be
non-dependent, but are mostly treated as dependent
Product: clang
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: unassignedclangbugs at nondot.org
Reporter: harald at gigawatt.nl
CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
Classification: Unclassified
Consider this test program, which uses ADL to detect whether expressions are
treated as dependent or as non-dependent. Non-dependent expressions are looked
up at template definition time, so find the void f(const char *s, ...)
function. Dependent expressions are looked up at template instantiation time
with ADL, and find the void f(const char *s, S1) function.
#include <cstdio>
void f(const char *s, ...) { std::printf("%s: non-dependent\n", s); }
struct S1 { };
template <typename T>
struct S2 {
static S1 a;
static S1 b() { return {}; }
template <typename U>
static U c() { return {}; }
static void z() {
f("S1()", S1());
f("T()", T());
f("a", a);
f("b()", b());
f("c<T>()", c<T>());
f("c<S1>()", c<S1>());
f("decltype(b())()", decltype(b())());
}
};
void f(const char *s, S1) { std::printf("%s: dependent\n", s); }
int main() {
S2<S1>::z();
}
The output with r223387
(http://llvm.org/builds/downloads/LLVM-3.6.0-r223387-win32.exe from 5 December)
is:
S1(): non-dependent
T(): dependent
a: non-dependent
b(): non-dependent
c<T>(): dependent
c<S1>(): dependent
decltype(b())(): dependent
Compilation flags used for testing: -std=c++11 -pedantic -Wall. No warnings or
errors are given.
The ones involving T are sanity checks: they're obviously dependent. All the
other ones should be non-dependent. The difference between b() and
decltype(b())() is particularly troubling to me: b() is treated as
non-dependent when used directly, and decltype(expr) is supposed to be
dependent if and only if expr is type-dependent, and T() is supposed to be
type-dependent if and only if T is dependent, yet decltype(b())() is treated as
dependent.
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