[clang] typeid() can only be used with <typeinfo>

[mikomikotaishi]

When compiling a translation unit that calls the typeid() operator, the compiler will compile the file only if <typeinfo> is #included. It will not compile when using import std; (or any module that re-exports std::type_info), for example, without any #include <typeinfo>.

I imagine this is not intended, as cppreference states that a program is ill-informed if it calls typeid() without std::type_info being visible, if a translation imports a module that re-exports std::type_info, it should in theory still work, yet it does not.

[llvmbot]

@llvm/issue-subscribers-clang-modules

Author: Miko (mikomikotaishi)

When compiling a translation unit that calls the `typeid()` operator, the compiler will compile the file only if `<typeinfo>` is `#include`d. It will not compile when using `import std;`, for example, without any `#include <typeinfo>`.

I imagine this is not intended, as cppreference states that a program is ill-informed if it calls typeid() without std::type_info being visible, if a translation imports a module that re-exports std::type_info, it should in theory still work, yet it does not.

[shafik]

CC @ChuanqiXu9 @mpark