Modifying Clang for a Safer, More Explicit C++

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Modifying Clang for a Safer, More Explicit C++

Modified C++ Inspired by the paper "Some Were Meant for C" by Stephen Kell, I decided to show that it's possible to iterate C++ to be safer, more explicit, and less error-prone. Here's a possible starting point: I didn't invent a new language or compiler, but took the world's best compiler, clang, and modified it to begin iterating towards a new furture of C++. Naming things is hard, so I call this 'Modified C++'. Some of the following could be implemented as tooling in a linter or checker, but the idea is to update the compiler directly. I also wanted to learn more about clang. This compiler needs a flag to enable/disable this functionality so that existing library code can be used with a 'diagnostic ignored' pragma. You can build clang using the normal non-bootstrap process and you'll be left with a clang that compiles C++ but with the following modifications: - All basic types (excluding pointers and references) are const by default and may be marked 'mutable' to allow them to be changed after declaration - Lambda capture lists must be explicit (no [&] or [=], by themselves) - Braces are required for conditional statements, case and default statements within switches, and loops - Implicit conversions to bool are prohibited (e.g., pointers must be compared against nullptr/NULL) - No goto support - Explicit 'rule of six' for classes must be programmer-implemented (default, copy, and move c'tors, copy and move assignment, d'tor) - No C style casts Here's an example program that's valid in Modified C++: mutable int main(int, char**) { mutable int x = 0; return x; } Here's another that will fail to compile: mutable int main(int, char**) { int x = 1; x = 0; // x is constant return x; } I'd like your feedback. Future changes I'm thinking about are: - feature flag for modified c++ to enable/disable with 'diagnostic ignored' pragma, to support existing headers and libraries - support enum classes only - constructor declarations are explicit by default - namespaces within classes - normalize lambda and free function syntax - your ideas here