diff --git a/CMakeLists.txt b/CMakeLists.txt
index 56d5ca6..a3cbf9e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -23,7 +23,7 @@ find_package(LLVM)
 
 include_directories(${CMAKE_SOURCE_DIR})
 
-BISON_TARGET(Parser generators/wraith.y ${CMAKE_CURRENT_BINARY_DIR}/y.tab.c COMPILE_FLAGS "-d -v -t -Wcounterexamples")
+BISON_TARGET(Parser generators/wraith.y ${CMAKE_CURRENT_BINARY_DIR}/y.tab.c COMPILE_FLAGS "-d -v -t")
 FLEX_TARGET(Scanner generators/wraith.lex ${CMAKE_CURRENT_BINARY_DIR}/lex.yy.c)
 
 ADD_FLEX_BISON_DEPENDENCY(Scanner Parser)
@@ -41,9 +41,11 @@ add_executable(
 	# Source
 	src/ast.h
 	src/codegen.h
+	src/identcheck.h
 	src/parser.h
     src/ast.c
 	src/codegen.c
+	src/identcheck.c
 	src/parser.c
 	src/main.c
 	# Generated code
diff --git a/commenttest.w b/commenttest.w
new file mode 100644
index 0000000..70cd73e
--- /dev/null
+++ b/commenttest.w
@@ -0,0 +1,6 @@
+struct Program { 
+    // This triggers a parse error
+    static Main(): int {
+        return 0;
+    }
+}
\ No newline at end of file
diff --git a/iftest.w b/iftest.w
new file mode 100644
index 0000000..efa5bfa
--- /dev/null
+++ b/iftest.w
@@ -0,0 +1,44 @@
+struct MyStruct {
+    static MyFunc(): int {
+        myStructInt: int = 595959959;
+        return myStructInt;
+    }
+}
+
+struct Program {
+    static Foo(): int {
+        return 0;
+    }
+
+    static Main(): int {
+        myInt: int = 54;
+        if (myInt < 0) {
+            signTag: int = 0 - 1;
+        } else if (myInt == 0) {
+            signTag: int = 0;
+        } else {
+            signTag: int = 1;
+        }
+
+        myBool: bool;
+        if (myBool) {
+            if (myBool) {
+                if (myBool) {
+                    if (myBool) {
+                        if (myBool) {
+                            lol: int = 69;
+                        }
+                    }
+                }
+            }
+        }
+
+        someInt: int = 9585858;
+
+        return 0;
+    }
+
+    static Bar(): int {
+        return 0;
+    }
+}
diff --git a/reftest.w b/reftest.w
new file mode 100644
index 0000000..ece6a0c
--- /dev/null
+++ b/reftest.w
@@ -0,0 +1,11 @@
+struct MyStruct {
+    foo: int;
+}
+
+struct Program {
+    static Main(): int {
+        myStruct: Reference<MyStruct>;
+        myStruct = alloc MyStruct;
+        return 0;
+    }
+}
\ No newline at end of file
diff --git a/src/ast.c b/src/ast.c
index 4f33a63..273739a 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -2,21 +2,8 @@
 
 #include <stdlib.h>
 #include <stdio.h>
-#include <string.h>
 
-char* strdup (const char* s)
-{
-    size_t slen = strlen(s);
-    char* result = malloc(slen + 1);
-
-    if(result == NULL)
-    {
-        return NULL;
-    }
-
-    memcpy(result, s, slen+1);
-    return result;
-}
+#include "util.h"
 
 const char* SyntaxKindString(SyntaxKind syntaxKind)
 {
@@ -29,6 +16,8 @@ const char* SyntaxKindString(SyntaxKind syntaxKind)
         case Comment: return "Comment";
         case CustomTypeNode: return "CustomTypeNode";
         case Declaration: return "Declaration";
+        case Expression: return "Expression";
+        case ForLoop: return "ForLoop";
         case DeclarationSequence: return "DeclarationSequence";
         case FunctionArgumentSequence: return "FunctionArgumentSequence";
         case FunctionCallExpression: return "FunctionCallExpression";
@@ -108,6 +97,7 @@ Node* MakeIdentifierNode(
     node->syntaxKind = Identifier;
     node->value.string = strdup(id);
     node->childCount = 0;
+    node->typeTag = NULL;
     return node;
 }
 
@@ -517,7 +507,12 @@ static void PrintNode(Node *node, int tabCount)
             break;
 
         case Identifier:
-            printf("%s", node->value.string);
+            if (node->typeTag == NULL) {
+                printf("%s", node->value.string);
+            } else {
+                char *type = TypeTagToString(node->typeTag);
+                printf("%s<%s>", node->value.string, type);
+            }
             break;
 
         case Number:
@@ -537,3 +532,77 @@ void PrintTree(Node *node, uint32_t tabCount)
         PrintTree(node->children[i], tabCount + 1);
     }
 }
+
+TypeTag* MakeTypeTag(Node *node) {
+    if (node == NULL) {
+        fprintf(stderr, "wraith: Attempted to call MakeTypeTag on null value.\n");
+        return NULL;
+    }
+
+    TypeTag *tag = (TypeTag*)malloc(sizeof(TypeTag));
+    switch (node->syntaxKind) {
+        case Type:
+            tag = MakeTypeTag(node->children[0]);
+            break;
+
+        case PrimitiveTypeNode:
+            tag->type = Primitive;
+            tag->value.primitiveType = node->primitiveType;
+            break;
+
+        case ReferenceTypeNode:
+            tag->type = Reference;
+            tag->value.referenceType = MakeTypeTag(node->children[0]);
+            break;
+
+        case CustomTypeNode:
+            tag->type = Custom;
+            tag->value.customType = strdup(node->value.string);
+            break;
+
+        case Declaration:
+            tag = MakeTypeTag(node->children[0]);
+            break;
+
+        case StructDeclaration:
+            tag->type = Custom;
+            tag->value.customType = strdup(node->children[0]->value.string);
+            printf("Struct tag: %s\n", TypeTagToString(tag));
+            break;
+
+        case FunctionDeclaration:
+            tag = MakeTypeTag(node->children[0]->children[1]);
+            break;
+
+        default:
+            fprintf(stderr, 
+                    "wraith: Attempted to call MakeTypeTag on"
+                    " node with unsupported SyntaxKind: %s\n",
+                    SyntaxKindString(node->syntaxKind));
+            return NULL;
+    }
+    return tag;
+}
+
+char* TypeTagToString(TypeTag *tag) {
+    if (tag == NULL) {
+        fprintf(stderr, "wraith: Attempted to call TypeTagToString with null value\n");
+        return NULL;
+    }
+
+    switch (tag->type) {
+        case Unknown:
+            return "Unknown";
+        case Primitive:
+            return PrimitiveTypeToString(tag->value.primitiveType);
+        case Reference: {
+            char *inner = TypeTagToString(tag->value.referenceType);
+            size_t innerStrLen = strlen(inner);
+            char *result = malloc(sizeof(char) * (innerStrLen + 5));
+            sprintf(result, "Ref<%s>", inner);
+            return result;
+        }
+        case Custom:
+            return tag->value.customType;
+    }
+}
\ No newline at end of file
diff --git a/src/ast.h b/src/ast.h
index 8e49ace..9c1312f 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -2,6 +2,7 @@
 #define WRAITH_AST_H
 
 #include <stdint.h>
+#include "identcheck.h"
 
 typedef enum
 {
@@ -71,6 +72,26 @@ typedef union
     BinaryOperator binaryOperator;
 } Operator;
 
+typedef struct TypeTag
+{
+    enum Type
+    {
+        Unknown,
+        Primitive,
+        Reference,
+        Custom
+    } type;
+    union
+    {
+        /* Valid when type = Primitive. */
+        PrimitiveType primitiveType;
+        /* Valid when type = Reference. */
+        struct TypeTag *referenceType;
+        /* Valid when type = Custom. */
+        char *customType;
+    } value;
+} TypeTag;
+
 typedef struct Node
 {
     SyntaxKind syntaxKind;
@@ -87,9 +108,10 @@ typedef struct Node
         uint64_t number;
     } value;
     PrimitiveType primitiveType;
+    TypeTag *typeTag;
+    IdNode *idLink;
 } Node;
 
-char* strdup (const char* s);
 const char* SyntaxKindString(SyntaxKind syntaxKind);
 
 uint8_t IsPrimitiveType(Node *typeNode);
@@ -211,5 +233,9 @@ Node* MakeForLoopNode(
 );
 
 void PrintTree(Node *node, uint32_t tabCount);
+const char* SyntaxKindString(SyntaxKind syntaxKind);
+
+TypeTag* MakeTypeTag(Node *node);
+char* TypeTagToString(TypeTag *tag);
 
 #endif /* WRAITH_AST_H */
diff --git a/src/identcheck.c b/src/identcheck.c
new file mode 100644
index 0000000..6fe0ec4
--- /dev/null
+++ b/src/identcheck.c
@@ -0,0 +1,328 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "ast.h"
+#include "identcheck.h"
+
+IdNode* MakeIdNode(NodeType type, char *name, IdNode *parent) {
+    IdNode *node = (IdNode*)malloc(sizeof(IdNode));
+    node->type = type;
+    node->name = strdup(name);
+    node->parent = parent;
+    node->childCount = 0;
+    node->childCapacity = 0;
+    node->children = NULL;
+    node->typeTag = NULL;
+    return node;
+}
+
+void AddChildToNode(IdNode *node, IdNode *child) {
+    if (child == NULL) return;
+
+    if (node->children == NULL) {
+        node->childCapacity = 2;
+        node->children = (IdNode**) malloc(sizeof(IdNode*) * node->childCapacity);
+    } else if (node->childCount == node->childCapacity) {
+        node->childCapacity *= 2;
+        node->children = (IdNode**) realloc(node->children, sizeof(IdNode*) * node->childCapacity);
+    }
+
+    node->children[node->childCount] = child;
+    node->childCount += 1;
+}
+
+IdNode* MakeIdTree(Node *astNode, IdNode *parent) {
+    uint32_t i;
+    IdNode *mainNode;
+    switch (astNode->syntaxKind) {
+        case Assignment: {
+            if (astNode->children[0]->syntaxKind == Declaration) {
+                return MakeIdTree(astNode->children[0], parent);
+            } else {
+                for (i = 0; i < astNode->childCount; i++) {
+                    AddChildToNode(parent, MakeIdTree(astNode->children[i], parent));
+                }
+                return NULL;
+            }
+        }
+
+        case IfStatement: {
+            mainNode = MakeIdNode(OrderedScope, "if", parent);
+            Node *clause = astNode->children[0];
+            Node *stmtSeq = astNode->children[1];
+            for (i = 0; i < clause->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(clause->children[i], mainNode));
+            }
+            for (i = 0; i < stmtSeq->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(stmtSeq->children[i], mainNode));
+            }
+            break;
+        }
+
+        case IfElseStatement: {
+            Node *ifNode = astNode->children[0];
+            Node *elseStmts = astNode->children[1];
+            mainNode = MakeIdNode(OrderedScope, "if-else", parent);
+            IdNode *ifBranch = MakeIdTree(ifNode, mainNode);
+            IdNode *elseBranch = MakeIdNode(OrderedScope, "else", mainNode);
+
+            AddChildToNode(mainNode, ifBranch);
+            for (i = 0; i < elseStmts->childCount; i++) {
+                AddChildToNode(elseBranch, MakeIdTree(elseStmts->children[i], elseBranch));
+            }
+            AddChildToNode(mainNode, elseBranch);
+            break;
+        }
+
+        case ForLoop: {
+            Node *loopDecl = astNode->children[0];
+            Node *loopBody = astNode->children[3];
+            mainNode = MakeIdNode(OrderedScope, "for-loop", parent);
+            AddChildToNode(mainNode, MakeIdTree(loopDecl, mainNode));
+            for (i = 0; i < loopBody->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(loopBody->children[i], mainNode));
+            }
+            break;
+        }
+
+        case Declaration: {
+            mainNode = MakeIdNode(Variable, astNode->children[1]->value.string, parent);
+            mainNode->typeTag = MakeTypeTag(astNode);
+            astNode->children[1]->typeTag = mainNode->typeTag;
+            break;
+        }
+
+        case StructDeclaration: {
+            Node *idNode = astNode->children[0];
+            Node *declsNode = astNode->children[1];
+            mainNode = MakeIdNode(Struct, idNode->value.string, parent);
+            mainNode->typeTag = MakeTypeTag(astNode);
+            for (i = 0; i < declsNode->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(declsNode->children[i], mainNode));
+            }
+            break;
+        }
+
+        case FunctionDeclaration: {
+            Node *sigNode = astNode->children[0];
+            Node *funcNameNode = sigNode->children[0];
+            Node *funcArgsNode = sigNode->children[2];
+            Node *bodyStatementsNode = astNode->children[1];
+            mainNode = MakeIdNode(Function, funcNameNode->value.string, parent);
+            mainNode->typeTag = MakeTypeTag(astNode);
+            astNode->children[0]->children[0]->typeTag = mainNode->typeTag;
+            for (i = 0; i < funcArgsNode->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(funcArgsNode->children[i], mainNode));
+            }
+            for (i = 0; i < bodyStatementsNode->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(bodyStatementsNode->children[i], mainNode));
+            }
+            break;
+        }
+
+        case DeclarationSequence: {
+            mainNode = MakeIdNode(UnorderedScope, "", parent);
+            for (i = 0; i < astNode->childCount; i++) {
+                AddChildToNode(mainNode, MakeIdTree(astNode->children[i], mainNode));
+            }
+            break;
+        }
+
+        case Identifier: {
+            mainNode = MakeIdNode(Placeholder, astNode->value.string, parent);
+            IdNode *lookupNode = LookupId(mainNode, NULL, astNode->value.string);
+            if (lookupNode == NULL) {
+                fprintf(stderr, "wraith: Could not find IdNode for id %s\n", astNode->value.string);
+                TypeTag *tag = (TypeTag*)malloc(sizeof(TypeTag));
+                tag->type = Unknown;
+                astNode->typeTag = tag;
+            } else {
+                astNode->typeTag = lookupNode->typeTag;
+            }
+            break;
+        }
+
+        default: {
+            for (i = 0; i < astNode->childCount; i++) {
+                AddChildToNode(parent, MakeIdTree(astNode->children[i], parent));
+            }
+            return NULL;
+        }
+    }
+
+    astNode->idLink = mainNode;
+    return mainNode;
+}
+
+void PrintIdNode(IdNode *node) {
+    if (node == NULL) {
+        fprintf(stderr, "wraith: Attempted to call PrintIdNode with null value.\n");
+        return;
+    }
+
+    switch(node->type) {
+        case Placeholder:
+            printf("Placeholder (%s)\n", node->name);
+            break;
+        case OrderedScope:
+            printf("OrderedScope (%s)\n", node->name);
+            break;
+        case UnorderedScope:
+            printf("UnorderedScope (%s)\n", node->name);
+            break;
+        case Struct:
+            printf("%s : %s\n", node->name, TypeTagToString(node->typeTag));
+            break;
+        case Function:
+            printf("%s : Function<%s>\n", node->name, TypeTagToString(node->typeTag));
+            break;
+        case Variable:
+            printf("%s : %s\n", node->name, TypeTagToString(node->typeTag));
+            break;
+    }
+}
+
+void PrintIdTree(IdNode *tree, uint32_t tabCount) {
+    if (tree == NULL) {
+        fprintf(stderr, "wraith: Attempted to call PrintIdTree on a null value.\n");
+        return;
+    }
+
+    uint32_t i;
+    for (i = 0; i < tabCount; i++) {
+        printf("| ");
+    }
+
+    PrintIdNode(tree);
+
+    for (i = 0; i < tree->childCount; i++) {
+        PrintIdTree(tree->children[i], tabCount + 1);
+    }
+}
+
+
+int PrintAncestors(IdNode *node) {
+    if (node == NULL) return -1;
+
+    int i;
+    int indent = 1;
+    indent += PrintAncestors(node->parent);
+    for (i = 0; i < indent; i++) {
+        printf(" ");
+    }
+    PrintIdNode(node);
+    return indent;
+}
+
+IdNode* LookdownId(IdNode *root, NodeType targetType, char *targetName) {
+    if (root == NULL) {
+        fprintf(stderr, "wraith: Attempted to call LookdownId on a null value.\n");
+        return NULL;
+    }
+
+    IdNode *result = NULL;
+    IdNode **frontier = (IdNode**)malloc(sizeof(IdNode*));
+    frontier[0] = root;
+    uint32_t frontierCount = 1;
+
+    while (frontierCount > 0) {
+        IdNode *current = frontier[0];
+
+        if (current->type == targetType && strcmp(current->name, targetName) == 0) {
+            result = current;
+            break;
+        }
+
+        uint32_t i;
+        for(i = 1; i < frontierCount; i++) {
+            frontier[i-1] = frontier[i];
+        }
+        size_t newSize = frontierCount + current->childCount - 1;
+        if (frontierCount != newSize) {
+            frontier = (IdNode**) realloc(frontier, sizeof(IdNode*) * newSize);
+        }
+        for (i = 0; i < current->childCount; i++) {
+            frontier[frontierCount + i - 1] = current->children[i];
+        }
+        frontierCount = newSize;
+    }
+
+    free(frontier);
+    return result;
+}
+
+bool ScopeHasOrdering(IdNode *node) {
+    switch (node->type) {
+        case OrderedScope:
+        case Function:
+        case Variable: /* this is only technically true */
+            return true;
+        default:
+            return false;
+    }
+}
+
+IdNode* LookupId(IdNode *node, IdNode *prev, char *target) {
+    if (node == NULL) {
+        return NULL;
+    }
+
+    if (strcmp(node->name, target) == 0 && node->type != Placeholder) {
+        return node;
+    }
+
+    /* If this is the start of our search, we should not attempt to look at child nodes. Only
+     * looking up the scope tree is valid at this point.
+     *
+     * This has the notable side-effect that this function will return NULL if you attempt to look
+     * up a struct's internals starting from the node representing the struct itself. This is
+     * because an IdNode corresponds to the location *where an identifier is first declared.* Thus,
+     * an identifier has no knowledge of identifiers declared "inside" of it.
+     */
+    if (prev == NULL) {
+        return LookupId(node->parent, node, target);
+    }
+
+    /* If the current node forms an ordered scope then we want to prevent ourselves from looking
+     * up identifiers declared after the scope we have just come from.
+     */
+    uint32_t idxLimit;
+    if (ScopeHasOrdering(node)) {
+        uint32_t i;
+        for (i = 0, idxLimit = 0; i < node->childCount; i++, idxLimit++) {
+            if (node->children[i] == prev) {
+                break;
+            }
+        }
+    } else {
+        idxLimit = node->childCount;
+    }
+
+    uint32_t i;
+    for (i = 0; i < idxLimit; i++) {
+        IdNode *child = node->children[i];
+        if (child == prev || child->type == Placeholder) {
+            /* Do not inspect the node we just came from or placeholders. */
+            continue;
+        }
+
+        if (strcmp(child->name, target) == 0) {
+            return child;
+        }
+
+        if (child->type == Struct) {
+            uint32_t j;
+            for (j = 0; j < child->childCount; j++) {
+                IdNode *grandchild = child->children[j];
+                if (strcmp(grandchild->name, target) == 0) {
+                    return grandchild;
+                }
+            }
+        }
+    }
+
+    return LookupId(node->parent, node, target);
+}
diff --git a/src/identcheck.h b/src/identcheck.h
new file mode 100644
index 0000000..2c75262
--- /dev/null
+++ b/src/identcheck.h
@@ -0,0 +1,46 @@
+/* Validates identifier usage in an AST. */
+
+#ifndef WRAITH_IDENTCHECK_H
+#define WRAITH_IDENTCHECK_H
+
+#include <stdint.h>
+
+#include "ast.h"
+
+struct TypeTag;
+struct Node;
+
+typedef enum NodeType {
+    Placeholder,
+    UnorderedScope,
+    OrderedScope,
+    Struct,
+    Function,
+    Variable
+} NodeType;
+
+typedef struct IdNode {
+    NodeType type;
+    char *name;
+    struct TypeTag *typeTag;
+    struct IdNode *parent;
+    struct IdNode **children;
+    uint32_t childCount;
+    uint32_t childCapacity;
+} IdNode;
+
+typedef struct IdStatus {
+    enum StatusCode {
+        Valid,
+    } StatusCode;
+} IdStatus;
+
+
+IdNode* MakeIdTree(struct Node *astNode, IdNode *parent);
+void PrintIdNode(IdNode *node);
+void PrintIdTree(IdNode *tree, uint32_t tabCount);
+int PrintAncestors(IdNode *node);
+IdNode* LookdownId(IdNode *root, NodeType targetType, char *targetName);
+IdNode* LookupId(IdNode *node, IdNode *prev, char* target);
+
+#endif /* WRAITH_IDENTCHECK_H */
diff --git a/src/main.c b/src/main.c
index 48a2301..f58f618 100644
--- a/src/main.c
+++ b/src/main.c
@@ -3,6 +3,7 @@
 
 #include "parser.h"
 #include "codegen.h"
+#include "identcheck.h"
 
 int main(int argc, char *argv[])
 {
@@ -64,6 +65,12 @@ int main(int argc, char *argv[])
                 }
                 else
                 {
+                    {
+                        IdNode *idTree = MakeIdTree(rootNode, NULL);
+                        PrintIdTree(idTree, /*tabCount=*/0);
+                        printf("\n");
+                        PrintTree(rootNode, /*tabCount=*/0);
+                    }
                     exitCode = Codegen(rootNode, optimizationLevel);
                 }
             }
diff --git a/src/util.c b/src/util.c
new file mode 100644
index 0000000..ae1654f
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,16 @@
+#include "util.h"
+
+#include <string.h>
+
+char* strdup (const char* s)
+{
+  size_t slen = strlen(s);
+  char* result = malloc(slen + 1);
+  if(result == NULL)
+  {
+    return NULL;
+  }
+
+  memcpy(result, s, slen+1);
+  return result;
+}
\ No newline at end of file
diff --git a/src/util.h b/src/util.h
new file mode 100644
index 0000000..99ffaa7
--- /dev/null
+++ b/src/util.h
@@ -0,0 +1,8 @@
+#ifndef WRAITH_UTIL_H
+#define WRAITH_UTIL_H
+
+#include <string.h>
+
+char* strdup (const char* s);
+
+#endif /* WRAITH_UTIL_H */
diff --git a/types.w b/types.w
new file mode 100644
index 0000000..f83e5e5
--- /dev/null
+++ b/types.w
@@ -0,0 +1,14 @@
+struct MyStruct {
+    foo: int;
+    bar: bool;
+    MyFunction(): int {
+        return foo * 420;
+    }
+}
+
+struct Program {
+    static Main(): int {
+        decl: Reference<Reference<Reference<Reference<Reference<MyStruct>>>>>;
+        return 0;
+    }
+}
\ No newline at end of file