https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89070
Bug ID: 89070
Summary: Attribute [[nodiscard]] should be ignored in
unevaluated contexts
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: d.frey at gmx dot de
Target Milestone: ---
Title says it all. In an unevaluated context, the result is never used anyways.
Other compilers do ignore [[nodiscard]] in those contexts already. Example
code:
struct A
{
[[nodiscard]] static int match() { return 42; }
};
template<typename T>
auto g() -> decltype( T::match(), bool() )
{
return T::match();
}
int main()
{
g<A>();
}
Leads to:
<source>: In substitution of 'template<class T> decltype ((T::match(), bool()))
g() [with T = A]':
<source>:14:10: required from here
<source>:7:31: warning: ignoring return value of 'static int A::match()',
declared with attribute nodiscard [-Wunused-result]
7 | auto g() -> decltype( T::match(), bool() )
| ~~~~~~~~^~
<source>:3:30: note: declared here
3 | [[nodiscard]] static int match() { return 42; }
| ^~~~~
Compiler returned: 0
See https://godbolt.org/z/OQEnaD
