Crash when the result of a MethodCallStatement is unused and resolves to a compile-time constant

[kfcripps]

The following P4 program:

header h_t {
    bit<8> f;
}

control C() {
    action bar() {
        h_t h;
        h.minSizeInBits();
    }

    table t {
        actions = { bar; }
        default_action = bar;
    }

    apply {
        t.apply();
    }
}

control proto();
package top(proto p);

top(C()) main;

crashes with:

Compiler Bug: t.p4(8): visitor returned non-MethodCallExpression type: 8
        h.minSizeInBits();
        ^^^^^^^^^^^^^^^^^

[kfcripps]

Seems like the TypeInference pass may transform an IR::MethodCallStatement's methodCall to an IR::Constant, but a methodCall must be an IR::MethodCallExpression.

        // Constant-fold constant expressions
        if (auto mem = expression->method->to<IR::Member>()) {
            auto type = typeMap->getType(mem->expr, true);
            if (((mem->member == IR::Type::minSizeInBits ||
                  mem->member == IR::Type::minSizeInBytes ||
                  mem->member == IR::Type::maxSizeInBits ||
                  mem->member == IR::Type::maxSizeInBytes)) &&
                !type->is<IR::Type_Extern>() && expression->typeArguments->size() == 0 &&
                expression->arguments->size() == 0) {
                auto max = mem->member.name.startsWith("max");
                int w = typeMap->widthBits(type, expression, max);
                LOG3("Folding " << mem << " to " << w);
                if (w < 0) return expression;
                if (mem->member.name.endsWith("Bytes")) w = ROUNDUP(w, 8);
                auto result = new IR::Constant(expression->srcInfo, w);
                auto tt = new IR::Type_Type(result->type);
                setType(result->type, tt);
                setType(result, result->type);
                setCompileTimeConstant(result);
                return result;
            }