Added Empty() struct

6 files changed, 25 insertions, 3 deletions

diff --git a/CHANGES.md b/CHANGES.md
index 776a1b07..fd51056e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -29,6 +29,8 @@
   arguments).
 - Added `table.with(other)`, `table.without(other)`,
   `table.intersection(other)`, and `table.difference(other)`.
+- Added `Empty` for a built-in empty struct type and `EMPTY` for an instance of
+  the empty struct.
 - Added a `--format` flag to the `tomo` binary that autoformats your code
   (currently unstable, do not rely on it just yet).
 - Standardized text methods for Unicode encodings:
diff --git a/src/environment.c b/src/environment.c
index 3f07787e..ea390996 100644
--- a/src/environment.c
+++ b/src/environment.c
@@ -68,6 +68,8 @@ env_t *global_env(bool source_mapping) {
     PATH_TYPE_TYPE = declare_type(env, "enum PathType(Relative, Absolute, Home)");
     PATH_TYPE = declare_type(env, "struct Path(type:PathType, components:[Text])");
 
+    type_t *empty_type = declare_type(env, "struct Empty()");
+
     typedef struct {
         const char *name, *code, *type_str;
     } ns_entry_t;
@@ -83,9 +85,10 @@ env_t *global_env(bool source_mapping) {
         Text_t typeinfo;
         List_t namespace;
     } global_types[] = {
-        MAKE_TYPE("Void", Type(VoidType), Text("Void_t"), Text("Void$info")),
+        MAKE_TYPE("Void", Type(VoidType), Text("void"), Text("Void$info")),
         MAKE_TYPE("Abort", Type(AbortType), Text("void"), Text("Abort$info")),
-        MAKE_TYPE("Memory", Type(MemoryType), Text("Memory_t"), Text("Memory$info")),
+        MAKE_TYPE("Memory", Type(MemoryType), Text("void"), Text("Memory$info")),
+        MAKE_TYPE("Empty", empty_type, Text("Empty$$type"), Text("Empty$$info")),
         MAKE_TYPE( //
             "Bool", Type(BoolType), Text("Bool_t"), Text("Bool$info"),
             {"parse", "Bool$parse", "func(text:Text, remainder:&Text? = none -> Bool?)"}),
@@ -531,6 +534,7 @@ env_t *global_env(bool source_mapping) {
         {"exit", "tomo_exit", "func(message:Text?=none, code=Int32(1) -> Abort)"},
         {"fail", "fail_text", "func(message:Text -> Abort)"},
         {"sleep", "sleep_num", "func(seconds:Num)"},
+        {"EMPTY", "EMPTY", "Empty"},
     };
 
     for (size_t i = 0; i < sizeof(global_vars) / sizeof(global_vars[0]); i++) {
diff --git a/src/stdlib/datatypes.h b/src/stdlib/datatypes.h
index fc665401..0ac97019 100644
--- a/src/stdlib/datatypes.h
+++ b/src/stdlib/datatypes.h
@@ -69,6 +69,9 @@ typedef struct table_s {
     struct table_s *fallback;
 } Table_t;
 
+typedef struct Empty$$struct {
+} Empty$$type;
+
 typedef struct {
     void *fn, *userdata;
 } Closure_t;
diff --git a/src/stdlib/structs.c b/src/stdlib/structs.c
index 885b903c..89b5581b 100644
--- a/src/stdlib/structs.c
+++ b/src/stdlib/structs.c
@@ -6,6 +6,7 @@
 #include "bools.h"
 #include "metamethods.h"
 #include "siphash.h"
+#include "structs.h"
 #include "text.h"
 #include "util.h"
 
@@ -214,3 +215,14 @@ void Struct$deserialize(FILE *in, void *outval, List_t *pointers, const TypeInfo
         }
     }
 }
+
+public
+const TypeInfo_t Empty$$info = {.size = 0,
+                                .align = 0,
+                                .tag = StructInfo,
+                                .metamethods = Struct$metamethods,
+                                .StructInfo.name = "Empty",
+                                .StructInfo.num_fields = 0};
+
+public
+const Empty$$type EMPTY = {};
diff --git a/src/stdlib/structs.h b/src/stdlib/structs.h
index a582e9fb..83904377 100644
--- a/src/stdlib/structs.h
+++ b/src/stdlib/structs.h
@@ -15,6 +15,8 @@ PUREFUNC bool PackedData$equal(const void *x, const void *y, const TypeInfo_t *t
 PUREFUNC Text_t Struct$as_text(const void *obj, bool colorize, const TypeInfo_t *type);
 void Struct$serialize(const void *obj, FILE *out, Table_t *pointers, const TypeInfo_t *type);
 void Struct$deserialize(FILE *in, void *outval, List_t *pointers, const TypeInfo_t *type);
+extern const TypeInfo_t Empty$$info;
+extern const Empty$$type EMPTY;
 
 #define Struct$metamethods                                                                                             \
     {                                                                                                                  \
diff --git a/src/stdlib/types.h b/src/stdlib/types.h
index bd2474fa..5cd622e7 100644
--- a/src/stdlib/types.h
+++ b/src/stdlib/types.h
@@ -91,7 +91,6 @@ struct TypeInfo_s {
 
 extern const TypeInfo_t Void$info;
 extern const TypeInfo_t Abort$info;
-#define Void_t void
 
 Text_t Type$as_text(const void *typeinfo, bool colorize, const TypeInfo_t *type);