Begin work adding bit_field

src/check_type.cpp

@@ -925,6 +925,144 @@ gb_internal void check_enum_type(CheckerContext *ctx, Type *enum_type, Type *nam
 	enum_type->Enum.max_value_index = max_value_index;
 }
 
+gb_internal bool is_valid_bit_field_backing_type(Type *type) {
+	if (type == nullptr) {
+		return nullptr;
+	}
+	type = base_type(type);
+	if (is_type_untyped(type)) {
+		return false;
+	}
+	if (is_type_integer(type)) {
+		return true;
+	}
+	if (type->kind == Type_Array) {
+		return is_type_integer(type->Array.elem);
+	}
+	return false;
+}
+
+gb_internal void check_bit_field_type(CheckerContext *ctx, Type *bit_field_type, Type *named_type, Ast *node) {
+	ast_node(bf, BitFieldType, node);
+	GB_ASSERT(is_type_bit_field(bit_field_type));
+
+	Type *backing_type = check_type(ctx, bf->backing_type);
+	if (backing_type == nullptr || !is_valid_bit_field_backing_type(backing_type)) {
+		error(node, "Backing type for a bit_field must be an integer or an array of an integer");
+		return;
+	}
+
+	bit_field_type->BitField.backing_type = backing_type;
+	bit_field_type->BitField.scope = ctx->scope;
+
+	auto fields    = array_make<Entity *>(permanent_allocator(), 0, bf->fields.count);
+	auto bit_sizes = array_make<u8>      (permanent_allocator(), 0, bf->fields.count);
+
+	u64 maximum_bit_size = 8 * type_size_of(backing_type);
+	u64 total_bit_size = 0;
+
+	for_array(i, bf->fields) {
+		i32 field_src_index = cast(i32)i;
+		Ast *field = bf->fields[i];
+		if (field->kind != Ast_BitFieldField) {
+			error(field, "Invalid AST for a bit_field");
+			continue;
+		}
+		ast_node(f, BitFieldField, field);
+		if (f->name == nullptr || f->name->kind != Ast_Ident) {
+			error(field, "A bit_field's field name must be an identifier");
+			continue;
+		}
+		CommentGroup *docs    = f->docs;
+		CommentGroup *comment = f->comment;
+
+		String name = f->name->Ident.token.string;
+
+		if (f->type == nullptr) {
+			error(field, "A bit_field's field must have a type");
+			continue;
+		}
+
+		Type *type = check_type(ctx, f->type);
+		if (type_size_of(type) > 8) {
+			error(f->type, "The type of a bit_field's field must be <= 8 bytes, got %lld", cast(long long)type_size_of(type));
+		}
+
+		if (is_type_untyped(type)) {
+			gbString s = type_to_string(type);
+			error(f->type, "The type of a bit_field's field must be a typed integer, enum, or boolean, got %s", s);
+			gb_string_free(s);
+		} else if (!(is_type_integer(type) || is_type_enum(type) || is_type_boolean(type))) {
+			gbString s = type_to_string(type);
+			error(f->type, "The type of a bit_field's field must be an integer, enum, or boolean, got %s", s);
+			gb_string_free(s);
+		}
+
+		if (f->bit_size == nullptr) {
+			error(field, "A bit_field's field must have a specified bit size");
+			continue;
+		}
+
+
+		Operand o = {};
+		check_expr(ctx, &o, f->bit_size);
+		if (o.mode != Addressing_Constant) {
+			error(f->bit_size, "A bit_field's specified bit size must be a constant");
+			o.mode = Addressing_Invalid;
+		}
+		if (o.value.kind == ExactValue_Float) {
+			o.value = exact_value_to_integer(o.value);
+		}
+
+		ExactValue bit_size = o.value;
+
+		if (bit_size.kind != ExactValue_Integer) {
+			gbString s = expr_to_string(f->bit_size);
+			error(f->bit_size, "Expected an integer constant value for the specified bit size, got %s", s);
+			gb_string_free(s);
+		}
+
+		if (scope_lookup_current(ctx->scope, name) != nullptr) {
+			error(f->name, "'%.*s' is already declared in this bit_field", LIT(name));
+		} else {
+			i64 bit_size_i64 = exact_value_to_i64(bit_size);
+			u8 bit_size_u8 = 0;
+			if (bit_size_i64 <= 0) {
+				error(f->bit_size, "A bit_field's specified bit size cannot be <= 0, got %lld", cast(long long)bit_size_i64);
+				bit_size_i64 = 1;
+			}
+			if (bit_size_i64 > 64) {
+				error(f->bit_size, "A bit_field's specified bit size cannot exceed 64 bits, got %lld", cast(long long)bit_size_i64);
+				bit_size_i64 = 64;
+			}
+			bit_size_u8 = cast(u8)bit_size_i64;
+
+			Entity *e = alloc_entity_field(ctx->scope, f->name->Ident.token, type, false, field_src_index);
+			e->Variable.docs    = docs;
+			e->Variable.comment = comment;
+
+			add_entity(ctx, ctx->scope, nullptr, e);
+			array_add(&fields, e);
+			array_add(&bit_sizes, bit_size_u8);
+			add_entity_use(ctx, field, e);
+		}
+	}
+
+	GB_ASSERT(fields.count <= bf->fields.count);
+
+	if (total_bit_size > maximum_bit_size) {
+		gbString s = type_to_string(backing_type);
+		error(node, "The numbers required %llu exceeds the backing type's (%s) bit size %llu",
+		      cast(unsigned long long)total_bit_size,
+		      s,
+		      cast(unsigned long long)maximum_bit_size);
+		gb_string_free(s);
+	}
+
+	bit_field_type->BitField.fields    = slice_from_array(fields);
+	bit_field_type->BitField.bit_sizes = slice_from_array(bit_sizes);
+}
+
 gb_internal bool is_type_valid_bit_set_range(Type *t) {
 	if (is_type_integer(t)) {
 		return true;
@@ -3051,6 +3189,20 @@ gb_internal bool check_type_internal(CheckerContext *ctx, Ast *e, Type **type, T
 		return true;
 	case_end;
 
+	case_ast_node(bf, BitFieldType, e);
+		bool ips = ctx->in_polymorphic_specialization;
+		defer (ctx->in_polymorphic_specialization = ips);
+		ctx->in_polymorphic_specialization = false;
+
+		*type = alloc_type_bit_field();
+		set_base_type(named_type, *type);
+		check_open_scope(ctx, e);
+		check_bit_field_type(ctx, *type, named_type, e);
+		check_close_scope(ctx);
+		(*type)->BitField.node = e;
+		return true;
+	case_end;
+
 
 	case_ast_node(pt, ProcType, e);
 		bool ips = ctx->in_polymorphic_specialization;