Outline view flattens symbols inside `operator""` (user-defined literal) function

Discussed in https://github.com/microsoft/vscode-cpptools/discussions/14019

^{Originally posted by coshz October 26, 2025}
I've noticed that VS Code outline view treats symbols inside user-defined literal function, instead of operator"" itself, as top-level symbols. Example code:

void operator""_T(const char* str, size_t n)
{
    auto foo = [](auto s) { return s; };
    std::string var_1 = std::string(str,n);
    foo(var_1);
    std::string var_2 = foo(var_1);
}

The outline view behavior (sort by position):

• observed: var_1, foo, var_2;
• expected: operator""_T(const char*, size_t).

Is this a known limitation of the symbol parser for user-defined literals?

Start with the minimal C++ user-defined literal example in the issue and inspect the outline symbol parsing path used by the VS Code extension. Done means the outline shows operator""_T as the function and nests var_1, foo, and var_2 instead of treating them as top-level symbols.