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Make union_ptr_t's constructor statically type safe

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Ensure it cannot be constructed from the wrong node type.
This commit is contained in:
ridiculousfish 2020-07-12 15:38:05 -07:00
parent 8d37be2916
commit a8eb2a6813
1 changed files with 23 additions and 20 deletions
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43
src/ast.h
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@ -103,6 +103,19 @@ const wchar_t *ast_type_to_string(type_t type);
* };
*/
namespace template_goo {
/// \return true if type Type is in the Candidates list.
template <typename Type>
constexpr bool type_in_list() {
return false;
}
template <typename Type, typename Candidate, typename... Rest>
constexpr bool type_in_list() {
return std::is_same<Type, Candidate>::value || type_in_list<Type, Rest...>();
}
} // namespace template_goo
// A union pointer field is a pointer to one of a fixed set of node types.
// It is never null after construction.
template <typename... Nodes>
@ -127,9 +140,8 @@ struct union_ptr_t {
template <typename Node>
/* implicit */ union_ptr_t(std::unique_ptr<Node> n) : contents(std::move(n)) {
// TODO: this could be made statically type safe.
assert(contents != nullptr && allows_node(*contents) &&
"union_ptr constructed from invalid node type");
static_assert(template_goo::type_in_list<Node, Nodes...>(),
"Cannot construct from this node type");
}
};
@ -153,7 +165,7 @@ struct optional_t {
bool has_value() const { return contents != nullptr; }
};
namespace horrible_template_goop {
namespace template_goo {
// void if B is true, SFINAE'd away otherwise.
template <bool B>
@ -198,14 +210,14 @@ void accept_field_visitor(FieldVisitor &v, bool reverse, Field &field, Rest &...
if (reverse) visit_1_field(v, field);
}
} // namespace horrible_template_goop
} // namespace template_goo
#define FIELDS(...) \
template <typename FieldVisitor> \
void accept(FieldVisitor &visitor, bool reversed = false) { \
visitor.will_visit_fields_of(*this); \
horrible_template_goop::accept_field_visitor(visitor, reversed, __VA_ARGS__); \
visitor.did_visit_fields_of(*this); \
#define FIELDS(...) \
template <typename FieldVisitor> \
void accept(FieldVisitor &visitor, bool reversed = false) { \
visitor.will_visit_fields_of(*this); \
template_goo::accept_field_visitor(visitor, reversed, __VA_ARGS__); \
visitor.did_visit_fields_of(*this); \
}
/// node_t is the base node of all AST nodes.
@ -778,15 +790,6 @@ bool keyword_t<KWs...>::allows_keyword(parse_keyword_t kw) {
return false;
}
// static
template <typename... Nodes>
bool union_ptr_t<Nodes...>::allows_node(const node_t &node) {
for (type_t t : {Nodes::AstType...}) {
if (t == node.type) return true;
}
return false;
}
/**
* A node visitor is like a field visitor, but adapted to only visit actual nodes, as const
* references. It calls the visit() function of its visitor with a const reference to each node