Symbol deduplication in CPP code has some missing cases

[herwinw]

I was just looking at the generated code for CONST ||= 1; 2 (the ; 2 is to turn the used mode off, I guess the last line is always used. This is without #2047, but the same things happens with that PR):

    symbols[0] = SymbolObject::intern("CONST", 5);
    symbols[1] = SymbolObject::intern("CONST", 5);

            Value is_defined_result1;
            try {
                auto const2 =  self->const_find_with_autoload(env, self, symbols[0]/*:CONST*/, Object::ConstLookupSearchMode::NotStrict);
                const2;
                is_defined_result1 = new StringObject("constant");
            } catch (ExceptionObject *) {
                is_defined_result1 = NilObject::the();
            }
            Value if_result3;
            if (is_defined_result1.public_send(env, "!"_s)->is_truthy()) {
                if_result3 = is_defined_result1.public_send(env, "!"_s);
            } else {
                auto const4 =  self->const_find_with_autoload(env, self, symbols[0]/*:CONST*/, Object::ConstLookupSearchMode::NotStrict);
                if_result3 = const4.public_send(env, "!"_s);
            }
            Value if_result5;
            if (if_result3->is_truthy()) {
                if_result5 =  self->const_set(symbols[1]/*:CONST*/, Value::integer(1));
            } else {
                ;
            }

The two calls to const_find_with_autoload both use the first symbol, whe call to const_set uses the second one. Both symbols are the same, and the code is created by the same node.name calls. So we should be able to merge these two values.

[herwinw]

With the power of $stderr.puts sprinkled in your code (who needs a debugger):

{:CONST=>0, "CONST"=>1}

ConstFindInstruction calls to_sym on the input, ConstSetInstruction calls to_s

So I guess we should fix this using https://api.rubyonrails.org/classes/ActiveSupport/HashWithIndifferentAccess.html (grabs popcorn)