[llvm-bugs] [Bug 43494] New: Improve diagnostics for trying to invoke a destructor on a qualified namespace

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43494

            Bug ID: 43494
           Summary: Improve diagnostics for trying to invoke a destructor
                    on a qualified namespace
           Product: clang
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: arcata at gmail.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

If you try to invoke the destructor on a `std::string`, and you don't already
know the answer for what you're supposed to write, then the diagnostics are not
helpful at best, and misleading at worst:

% cat ~/foo.cpp          
#include <string>
void destroyString(std::string &&s) {
  s.~string();
}

% xcrun clang++ ~/foo.cpp
/Users/jgroff/foo.cpp:3:6: error: identifier 'string' in object destruction
expression does not name
      a type
  s.~string();
     ^


% cat ~/foo1.cpp
#include <string>
void destroyString(std::string &&s) {
  s.~std::string();
}

% clang++ ~/foo1.cpp
/Users/jgroff/foo1.cpp:3:5: error: '~' in destructor name should be after
nested name specifier
  s.~std::string();
    ^
          ~
/Users/jgroff/foo.cpp:3:5: error: qualified member access refers to a member in
namespace 'std'
  s.~std::string();
    ^~~~~~

% cat ~/foo2.cpp          
#include <string>
void destroyString(std::string &&s) {
  s.std::~string();
}

% clang++ ~/foo2.cpp
/Users/jgroff/foo2.cpp:3:10: error: qualified member access refers to a member
in namespace 'std'
  s.std::~string();
    ~~~~~^


% cat ~/foo3.cpp          
#include <string>
void destroyString(std::string &&s) {
  s.std::string::~string();
}

% clang++ ~/foo3.cpp
/Users/jgroff/foo3.cpp:3:19: error: expected the class name after '~' to name a
destructor
  s.std::string::~string();
                  ^


Any of these diagnostics seem like they could offer a fixit directly to the
correct syntax for what the user is trying to write, `s.~basic_string()`.

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