MSVC10中奇怪的编译器错误

Question

I've got the following code:

std::for_each(tokens.begin(), tokens.end(), [&](Token& t) {
    static const std::unordered_map<std::wstring, Wide::Lexer::TokenType> mapping([]() -> std::unordered_map<std::wstring, Wide::Lexer::TokenType>
    {
        // Maps strings to TokenType enumerated values
        std::unordered_map<std::wstring, Wide::Lexer::TokenType> result;

        // RESERVED WORD
        result[L"namespace"] = Wide::Lexer::TokenType::Namespace;
        result[L"for"] = Wide::Lexer::TokenType::For;
        result[L"while"] = Wide::Lexer::TokenType::While;
        result[L"do"] = Wide::Lexer::TokenType::Do;
        result[L"type"] = Wide::Lexer::TokenType::Type;

        // PUNCTUATION
        result[L"{"] = Wide::Lexer::TokenType::OpenCurlyBracket;
        result[L"}"] = Wide::Lexer::TokenType::CloseCurlyBacket;
        return result;
    }());
    if (mapping.find(t.Codepoints) != mapping.end()) {
        t.type = mapping.find(t.Codepoints)->second;
        return;
    }
    t.type = Wide::Lexer::TokenType::Identifier; // line 121
});

This iterates through a list of tokens, and judging by the contents of the codepoints, assigns them a value from the associated enum. If it's not found, then give it a value of "Identifier". But this fails to compile.

1>Lexer.cpp(121): error C2065: '__this' : undeclared identifier
1>Lexer.cpp(121): error C2227: left of '->Identifier' must point to class/struct/union/generic type

This is the full error, no warnings, no other errors. What? How can I fix this error?

Edit: I did some significant refactoring, and I've got the exact same problem in a somewhat simpler lambda.

auto end_current_token = [&] {
    if (current != Wide::Lexer::Token()) {

        current.type = Wide::Lexer::TokenType::Identifier; // error line

        if (reserved_words.find(current.Codepoints) != reserved_words.end())
            current.type = reserved_words.find(current.Codepoints)->second;
        if (punctuation.find(current.Codepoints[0]) != punctuation.end())
            current.type = punctuation.find(current.Codepoints[0])->second;

        tokens.push_back(current);
        current = Wide::Lexer::Token();
    }
};

I've cleaned and rebuilt the project.

I fixed the problem.

auto end_current_token = [&] {
    if (current != Wide::Lexer::Token()) {

        // WORKAROUND compiler bug- dead code
        struct bug_workaround_type {
            int Identifier;
        };
        bug_workaround_type bug;
        bug_workaround_type* __this = &bug;

        current.type = Wide::Lexer::TokenType::Identifier;

        if (reserved_words.find(current.Codepoints) != reserved_words.end())
            current.type = reserved_words.find(current.Codepoints)->second;
        if (punctuation.find(current.Codepoints[0]) != punctuation.end())
            current.type = punctuation.find(current.Codepoints[0])->second;

        tokens.push_back(current);
        current = Wide::Lexer::Token();
    }
};

No, really. Now it compiles and runs just fine.

Answer 1

I've got the same problem right now. I used other types, but for your case it will be like this:

auto end_current_token = [&] {

    using Wide::Lexer::TokenType;           // <-- this line solves problem

    if (current != Wide::Lexer::Token()) {
        current.type = Wide::Lexer::TokenType::Identifier;

Now it compiles well.

Answer 2

FWIW I tried to concoct a minimal working sample in order to compile on VS2010 and compiled the following without error.

#include <string>
#include <vector>
#include <algorithm>
#include <unordered_map>

namespace Wide { namespace Lexer {
    enum TokenType
    {
        OpenCurlyBracket,
        CloseCurlyBacket,
        Namespace,
        For,
        While,
        Do,
        Type,
        Identifier,
    };
} }

struct Token
{
    std::wstring Codepoints;
    Wide::Lexer::TokenType type;
};

int main()
{
    std::vector<Token> tokens;
    std::for_each(tokens.begin(), tokens.end(), [&](Token& t) {
        static const std::unordered_map<std::wstring, Wide::Lexer::TokenType> mapping([]() -> std::unordered_map<std::wstring, Wide::Lexer::TokenType>
        {
            // Maps strings to TokenType enumerated values
            std::unordered_map<std::wstring, Wide::Lexer::TokenType> result;

            // RESERVED WORD
            result[L"namespace"] = Wide::Lexer::TokenType::Namespace;
            result[L"for"] = Wide::Lexer::TokenType::For;
            result[L"while"] = Wide::Lexer::TokenType::While;
            result[L"do"] = Wide::Lexer::TokenType::Do;
            result[L"type"] = Wide::Lexer::TokenType::Type;

            // PUNCTUATION
            result[L"{"] = Wide::Lexer::TokenType::OpenCurlyBracket;
            result[L"}"] = Wide::Lexer::TokenType::CloseCurlyBacket;
            return result;
        }());
        if (mapping.find(t.Codepoints) != mapping.end()) {
            t.type = mapping.find(t.Codepoints)->second;
            return;
        }
        t.type = Wide::Lexer::TokenType::Identifier; // line 121
    });
}

Could you bisect the minimum edit that show the problem, starting from this code?