mie: add data structures to represent type-instances

unlike values, type-instances represent specialisations of parametised types.
they behave like concrete implementations of C++ template types.

for example: arith.int represents an integer type of unspecified bit-width.
a type-instance of this type would be arith.int<32> (or i32 for short) which
has a defined width of 32 bits.

mie/include/mie/type/function.h

@@ -0,0 +1,20 @@
+#ifndef MIE_TYPE_FUNCTION_H_
+#define MIE_TYPE_FUNCTION_H_
+
+#include <mie/type/type.h>
+#include <mie/vector.h>
+
+struct mie_function_type {
+	struct mie_type func_base;
+
+	MIE_VECTOR_DECLARE(struct mie_type *, func_in);
+	MIE_VECTOR_DECLARE(struct mie_type *, func_out);
+};
+
+MIE_API struct mie_function_type *mie_function_type_create(void);
+MIE_API void mie_function_type_add_in_part(
+	struct mie_function_type *ty, struct mie_type *part);
+MIE_API void mie_function_type_add_out_part(
+	struct mie_function_type *ty, struct mie_type *part);
+
+#endif

mie/include/mie/type/storage.h

@@ -0,0 +1,17 @@
+#ifndef MIE_TYPE_STORAGE_H_
+#define MIE_TYPE_STORAGE_H_
+
+#include <mie/type/type.h>
+#include <mie/vector.h>
+
+struct mie_storage_type {
+	struct mie_type st_base;
+
+	MIE_VECTOR_DECLARE(struct mie_type *, st_parts);
+};
+
+MIE_API struct mie_storage_type *mie_storage_type_create(void);
+MIE_API void mie_storage_type_add_part(
+	struct mie_storage_type *ty, struct mie_type *part);
+
+#endif

mie/include/mie/type/type.h

@@ -0,0 +1,31 @@
+#ifndef MIE_TYPE_TYPE_H_
+#define MIE_TYPE_TYPE_H_
+
+#include <mie/id.h>
+#include <mie/misc.h>
+#include <stddef.h>
+
+struct mie_dialect;
+struct mie_dialect_type;
+
+struct mie_type;
+
+/* a mie_type is an instance of mie_dialect_type.
+ * if the mie_dialect_type is a parametised type, the resulting mie_type
+ * will have those parameters baked in.
+ * this is a base struct. dialects that defined their own types do so by
+ * inheriting from this struct. */
+struct mie_type {
+	/* this is NOT the same as ty_def->ty_id */
+	mie_id ty_id;
+
+	/* this pointer is optional. if it is NULL, the name of the type can
+	 * be found in ty_def */
+	char *ty_name;
+
+	struct mie_dialect_type *ty_def;
+};
+
+MIE_API struct mie_type *mie_type_create(struct mie_dialect_type *type);
+
+#endif