为什么clang不对模板中的无效代码发出警告？

Question

When compiling with -Weverything, why would clang not flag the dead code in the template below, but flag it in the function? Note that in both cases, it flags the unused variable warning.

#include <iostream>

template <class Item> class ItemBase {
  public:
    bool performWork() {
        int i;
        std::cout << "foo" << std::endl;
        return true;
        std::cout << "dead code in template" << std::endl;
    }
};

bool badFunc();
bool badFunc() {
    int i;
    std::cout << "foo" << std::endl;
    return true;
    std::cout << "dead code in function" << std::endl;
}

int main() {
    ItemBase<float> tester;
    tester.performWork();

    badFunc();
}

clang output:

test.cpp:24:13: warning: unused variable 'i' [-Wunused-variable]
        int i;
            ^
test.cpp:33:9: warning: unused variable 'i' [-Wunused-variable]
    int i;
        ^
test.cpp:36:42: warning: code will never be executed [-Wunreachable-code]
    std::cout << "dead code in function" << std::endl;
                                         ^~
3 warnings generated.

Answer 1

I don't see that there's any reason for that warning not being emitted (other than a bug in clang).

I'm guessing clang is being over-cautious about warnings in templates since it isn't able to tell that code will never be executed by any instantiation of the template (even though it's obvious to a human), so it just doesn't warn. But that's just an assumption.