diff --git a/v0/ast.h b/v0/ast.h
index 348713f..cd6d270 100644
--- a/v0/ast.h
+++ b/v0/ast.h
@@ -5,29 +5,79 @@
 #define AST_H
 
 #include "bool.h"
+#include "token.h"
+
 #include <stddef.h>
 
 typedef struct {
-    /* @brief The name of the module being imported. */
-    char* module_name;
+    /** @brief The name of the module being imported. */
+    Token module_name;
 
-    /* @brief Whether the import is public or not. */
+    /** @brief Whether the import is public or not. */
     bool is_public;
 } ImportDeclaration;
 
+typedef enum {
+    TYPE_EXPRESSION_BUILTIN,
+    TYPE_EXPRESSION_ARRAY
+} TypeExpressionTag;
+
+/**
+ * An expression that evaluates to a type.
+ */
+typedef struct TypeExpression TypeExpression;
+struct TypeExpression{
+    /** @brief defines which entry in the union is valid */
+    TypeExpressionTag tag;
+    union {
+        /** @brief Evaluates to an array of the given type. */
+        struct {
+            /** @brief A pointer to the type of the elements stored in the array. */
+            TypeExpression* array;
+        } array;
+        /** @brief Evaluates to a builtin integer type.*/
+        struct {
+            /**
+             * @brief The number of bits in the integer.
+             * Typical values are 8, 16, 32, and 64.
+             */
+            int bitSize;
+            /** @brief `true` if the type is signed, `false` if it's unsigned. */
+            bool isSigned;
+        } builtin;
+    };
+};
+
+/**
+ * A declaration that aliases one type to another.
+ */
+typedef struct {
+    /** @brief The name of the alias. */
+    Token name;
+
+    /** @brief The value of the alias. */
+    TypeExpression value;
+} AliasDeclaration;
+
 /**
  * The top-level model.
  * Every file matches an entire Module.
  */
 typedef struct {
-    /* @brief The name of the module. */
-    char* name;
+    /** @brief The name of the module. */
+    Token name;
 
-    /* @brief The list of imports in the module. */
+    /** @brief The list of imports in the module. */
     ImportDeclaration* imports;
 
-    /* @brief The number of imports in the module. */
+    /** @brief The number of imports in the module. */
     size_t import_count;
+
+    /** @brief The list of aliases in the module. */
+    AliasDeclaration* aliases;
+
+    /** @brief The number of aliases in the module. */
+    size_t alias_count;
 } Module;
 
 #endif
diff --git a/v0/parser.c b/v0/parser.c
index 87c7a7d..5459bc5 100644
--- a/v0/parser.c
+++ b/v0/parser.c
@@ -28,18 +28,11 @@ Module* parser_parse(TokenStream* ts) {
         fprintf(stderr, "Out of memory\n");
         exit(1);
     }
-    module->name = NULL;
+    module->name = t;
     module->imports = NULL;
     module->import_count = 0;
-
-	module->name = (char*)malloc(t.text.length + 1);
-	if (module->name == NULL) {
-		fprintf(stderr, "Out of memory\n");
-		exit(1);
-	}
-
-	memcpy(module->name, t.text.data, t.text.length);
-	module->name[t.text.length] = '\0';
+    module->aliases = NULL;
+    module->alias_count = 0;
 
 	t = tokenstream_next(ts);
 	if (t.token != TOKEN_SEMICOLON) {
@@ -77,14 +70,8 @@ Module* parser_parse(TokenStream* ts) {
 			return NULL;
 		}
 
-		module->imports[module->import_count].module_name = (char*)malloc(t.text.length + 1);
-		if (!module->imports[module->import_count].module_name) {
-			fprintf(stderr, "Out of memory\n");
-			exit(1);
-		}
-		memcpy(module->imports[module->import_count].module_name, t.text.data, t.text.length);
-		module->imports[module->import_count].module_name[t.text.length] = '\0';
-		module->imports[module->import_count].is_public = is_public;
+		module->imports[module->import_count].module_name = t;
+		module->imports[module->import_count].is_public = (bool)is_public;
 		module->import_count++;
 
 		t = tokenstream_next(ts);
@@ -101,13 +88,10 @@ Module* parser_parse(TokenStream* ts) {
 void parser_free(Module* module) {
 	if (module == NULL) return;
     if (module->imports != NULL) {
-        /* C89: declare index variable before the loop */
-        size_t i;
-        for (i = 0; i < module->import_count; i++) {
-            free(module->imports[i].module_name);
-        }
         free(module->imports);
     }
-	free(module->name);
+    if (module->aliases != NULL) {
+        free(module->aliases);
+    }
 	free(module);
 }
diff --git a/v0/test_parser.c b/v0/test_parser.c
index 6484fde..c9767e9 100644
--- a/v0/test_parser.c
+++ b/v0/test_parser.c
@@ -1,13 +1,19 @@
 #include "test.h"
 #include "parser.h"
 #include <string.h>
+#include <stdlib.h>
 
 static void test_parser_module_name(void) {
 	TokenStream* ts = tokenstream_open("test.c", "module my_module;");
 	Module* m = parser_parse(ts);
+    char* buf;
 
 	assert_not_null(m, "expected module to be parsed");
-	assert_str("my_module", m->name, "expected name 'my_module'");
+    buf = malloc(m->name.text.length + 1);
+    memcpy(buf, m->name.text.data, m->name.text.length);
+    buf[m->name.text.length] = '\0';
+	assert_str("my_module", buf, "expected name 'my_module'");
+    free(buf);
 
 	parser_free(m);
 	tokenstream_close(ts);
@@ -56,13 +62,22 @@ static void test_parser_bad_import_name(void) {
 static void test_parser_imports(void) {
 	TokenStream* ts = tokenstream_open("test.c", "module my_module; import other_module;");
 	Module* m = parser_parse(ts);
+    char* buf;
 
 	assert_not_null(m, "expected module to be parsed");
-	assert_str("my_module", m->name, "expected name 'my_module'");
+    buf = malloc(m->name.text.length + 1);
+    memcpy(buf, m->name.text.data, m->name.text.length);
+    buf[m->name.text.length] = '\0';
+	assert_str("my_module", buf, "expected name 'my_module'");
+    free(buf);
 	
 	assert_not_null(m->imports, "expected imports to be parsed");
-	assert_int(1, m->import_count, "expected one import");
-	assert_str("other_module", m->imports[0].module_name, "expected import name 'other_module'");
+	assert_int(1, (int)m->import_count, "expected one import");
+    buf = malloc(m->imports[0].module_name.text.length + 1);
+    memcpy(buf, m->imports[0].module_name.text.data, m->imports[0].module_name.text.length);
+    buf[m->imports[0].module_name.text.length] = '\0';
+	assert_str("other_module", buf, "expected import name 'other_module'");
+    free(buf);
 	assert_false(m->imports[0].is_public, "expected import to not be public");
 
 	parser_free(m);
@@ -72,13 +87,22 @@ static void test_parser_imports(void) {
 static void test_parser_public_imports(void) {
 	TokenStream* ts = tokenstream_open("test.c", "module my_module; import public other_module;");
 	Module* m = parser_parse(ts);
+    char* buf;
 
 	assert_not_null(m, "expected module to be parsed");
-	assert_str("my_module", m->name, "expected name 'my_module'");
+    buf = malloc(m->name.text.length + 1);
+    memcpy(buf, m->name.text.data, m->name.text.length);
+    buf[m->name.text.length] = '\0';
+	assert_str("my_module", buf, "expected name 'my_module'");
+    free(buf);
 	
 	assert_not_null(m->imports, "expected imports to be parsed");
-	assert_int(1, m->import_count, "expected one import");
-	assert_str("other_module", m->imports[0].module_name, "expected import name 'other_module'");
+	assert_int(1, (int)m->import_count, "expected one import");
+    buf = malloc(m->imports[0].module_name.text.length + 1);
+    memcpy(buf, m->imports[0].module_name.text.data, m->imports[0].module_name.text.length);
+    buf[m->imports[0].module_name.text.length] = '\0';
+	assert_str("other_module", buf, "expected import name 'other_module'");
+    free(buf);
 	assert_true(m->imports[0].is_public, "expected import to be public");
 
 	parser_free(m);