Did a bit of refactoring and fixed the syntax so the union structs all have proper names.

expr.h

@@ -4,41 +4,44 @@
 #include "scanner.h"
 
 typedef enum {
-    Expression,
-    Literal,
-    Grouping,
-    Unary,
-    Binary,
-    Operator
+    EXPRESSION,
+    LITERAL,
+    GROUPING,
+    UNARY,
+    BINARY,
+    OPERATOR
 } ExpressionType;
 
-typedef struct {
-    ExpressionType type;
-    union ex {
-        struct binary;
-        struct grouping;
-        struct literal;
-        struct unary;
-    } expression;
-} Expr;
+typedef struct Expr expression;
 
-typedef struct {
-    Expr left;
+struct binary {
+    Expr* left;
     TokenType op;
-    Expr right;
-} binary;
+    Expr* right;
+};
 
 struct grouping {
-    Expr expression;
+    Expr* expression;
 };
 
 struct literal {
-    char* object;
+    TokenType type; //Probably something to this effect.
+    void* object;
 };
 
 struct unary {
     TokenType op;
-    Expr right;
+    Expr* right;
+};
+
+struct Expr {
+    ExpressionType type;
+    union ex {
+        struct binary Binary;
+        struct grouping Grouping;
+        struct literal Literal;
+        struct unary Unary;
+    } expression;
 };
 
 #endif