diff --git a/base_data_structures.cpp b/base_data_structures.cpp
index e6193dd..3dfcb12 100644
--- a/base_data_structures.cpp
+++ b/base_data_structures.cpp
@@ -302,7 +302,7 @@ intern_string(Intern_Table *t, String string) {
 //-----------------------------------------------------------------------------
 // Array List
 //-----------------------------------------------------------------------------
-const int LIST_DEFAULT_BLOCK_SIZE = 32;
+const int LIST_DEFAULT_BLOCK_SIZE = 16;
 const int LIST_DEFAULT_ALLOCATION_MUL = 2;
 
 template <class T>
diff --git a/core_ast.cpp b/core_ast.cpp
index 0369402..6d6090f 100644
--- a/core_ast.cpp
+++ b/core_ast.cpp
@@ -20,6 +20,17 @@ _ast_new(size_t size, Ast_Kind kind, Token *pos, Ast_Flag flags = 0) {
     return result;
 }
 
+CORE_Static void
+propagate_polymorphic(Ast *to, Ast *from) {
+    if (is_flag_set(from->flags, AST_IDENT_POLYMORPH)) set_flag(to->flags, AST_IDENT_POLYMORPH);
+    if (is_flag_set(from->flags, AST_TYPE_POLYMORPH)) set_flag(to->flags, AST_TYPE_POLYMORPH);
+}
+
+CORE_Static void
+propagate_polymorphic(Ast *to, Token *from) {
+    if (from->kind == TK_Polymorph) set_flag(to->flags, AST_IDENT_POLYMORPH);
+}
+
 CORE_Static Ast_Atom *
 ast_str(Token *pos, Intern_String string) {
     AST_NEW(Atom, VALUE, pos, AST_EXPR | AST_ATOM);
@@ -214,11 +225,13 @@ finalize_stmt_scope(Ast_Scope *scope) {
 }
 
 CORE_Static Ast_Decl *
-ast_struct(Token *pos, Ast_Scope *scope, Ast_Kind kind = AST_STRUCT) {
+ast_struct(Token *pos, Ast_Scope *scope, Ast_Kind kind, Array<Ast_Decl *> polymorph_parameters) {
     assert(kind == AST_STRUCT || kind == AST_UNION);
     AST_NEW(Decl, STRUCT, pos, AST_DECL | AST_AGGREGATE);
     result->kind = kind;
     result->scope = scope;
+    result->polymorph_parameters = polymorph_parameters;
+    if (polymorph_parameters.len) set_flag(result->flags, AST_POLYMORPH);
     return result;
 }
 
diff --git a/core_compiler_interface.hpp b/core_compiler_interface.hpp
index 4de6999..c31fdad 100644
--- a/core_compiler_interface.hpp
+++ b/core_compiler_interface.hpp
@@ -348,19 +348,22 @@ enum Ast_Kind : uint32_t {
 
 typedef uint32_t Ast_Flag;
 enum {
-    AST_EXPR = 1ull << 1,
-    AST_STMT = 1ull << 2,
-    AST_STRICT = 1ull << 3,
-    AST_AGGREGATE = 1ull << 4,
-    AST_AGGREGATE_CHILD = 1ull << 5,
-    AST_ATOM = 1ull << 7,
-    AST_FOREIGN = 1ull << 8,
-    AST_DECL = 1ull << 9,
-    AST_GLOBAL = 1ull << 10,
-    AST_FLAG = 1ull << 11,
-    AST_VAR_IS_CONST = 1ull << 12,
-    AST_OPERATOR_OVERLOAD = 1ull << 13,
-    AST_IS_LVALUE = 1ull << 14,
+    AST_EXPR = 1 << 1,
+    AST_STMT = 1 << 2,
+    AST_STRICT = 1 << 3,
+    AST_AGGREGATE = 1 << 4,
+    AST_AGGREGATE_CHILD = 1 << 5,
+    AST_ATOM = 1 << 7,
+    AST_FOREIGN = 1 << 8,
+    AST_DECL = 1 << 9,
+    AST_GLOBAL = 1 << 10,
+    AST_FLAG = 1 << 11,
+    AST_VAR_IS_CONST = 1 << 12,
+    AST_OPERATOR_OVERLOAD = 1 << 13,
+    AST_IS_LVALUE = 1 << 14,
+    AST_IDENT_POLYMORPH = 1 << 15,
+    AST_TYPE_POLYMORPH = 1 << 16,
+    AST_POLYMORPH = AST_IDENT_POLYMORPH | AST_TYPE_POLYMORPH,
 };
 
 struct Ast {
@@ -599,6 +602,7 @@ struct Ast_Decl : Ast {
 
     uint64_t operator_overload_arguments_hash;
     Ast_Operator_Info *overload_op_info;
+    Array<Ast_Decl *> polymorph_parameters;
 
     Ast_Scope *scope;
     Ast_Expr *typespec;
diff --git a/core_parsing.cpp b/core_parsing.cpp
index 6e6c5e1..39f04e8 100644
--- a/core_parsing.cpp
+++ b/core_parsing.cpp
@@ -457,22 +457,26 @@ parse_stmt_scope(Ast_Scope *scope_defined_outside = 0) {
     return scope;
 }
 
-CORE_Static Ast_Lambda *
-parse_lambda(Token *token) {
-    Scratch_Scope scratch(pctx->scratch);
-
-    Array<Ast_Decl *> params = {scratch.arena};
+CORE_Static Array<Ast_Decl *>
+parse_parameter_list(Arena *arena) {
+    Array<Ast_Decl *> params = {arena};
     if (!token_is(TK_CloseParen)) {
         for (;;) {
             Token *name = token_get();
-            if (token_match(TK_Identifier)) {
+            if (name->kind == TK_Identifier || name->kind == TK_Polymorph) {
+                token_next();
                 token_expect(TK_Colon);
+
                 Ast_Decl *param = ast_new(Ast_Decl, AST_VAR, name, AST_DECL);
                 param->name = name->intern_val;
-
                 param->typespec = parse_expr();
-                if (token_match(TK_Assign))
+
+                propagate_polymorphic(param, param->typespec);
+                propagate_polymorphic(param, name);
+
+                if (token_match(TK_Assign)) {
                     param->expr = parse_expr();
+                }
 
                 params.add(param);
             }
@@ -483,7 +487,14 @@ parse_lambda(Token *token) {
         }
     }
     token_expect(TK_CloseParen);
+    return params;
+}
 
+CORE_Static Ast_Lambda *
+parse_lambda(Token *token) {
+    Scratch_Scope scratch(pctx->scratch);
+
+    Array<Ast_Decl *> params = parse_parameter_list(scratch.arena);
     Array<Ast_Expr *> ret = {scratch.arena};
     if (token_match(TK_Colon)) {
         do {
@@ -588,18 +599,26 @@ parse_expr(S64 min_bp) {
     switch (token->kind) {
         case TK_StringLit: left = ast_str(token, token->intern_val); break;
         case TK_Identifier: left = ast_ident(token, token->intern_val); break;
+        case TK_Polymorph: left = ast_ident(token, token->intern_val); break;
         case TK_Integer: left = ast_int(token, token->int_val); break;
         case TK_UnicodeLit: left = ast_int(token, token->unicode); break;
         case TK_Float: left = ast_float(token, token->f64_val); break;
-        case TK_Pointer: left = ast_expr_unary(token, TK_Pointer, parse_expr(prefix_bp.right)); break;
-        case TK_Dereference: left = ast_expr_unary(token, TK_Dereference, parse_expr(prefix_bp.right)); break;
         case TK_Sub: left = ast_expr_unary(token, TK_Sub, parse_expr(prefix_bp.right)); break;
         case TK_Add: left = ast_expr_unary(token, TK_Add, parse_expr(prefix_bp.right)); break;
         case TK_Not: left = ast_expr_unary(token, TK_Not, parse_expr(prefix_bp.right)); break;
         case TK_Neg: left = ast_expr_unary(token, TK_Neg, parse_expr(prefix_bp.right)); break;
         case TK_Increment: left = ast_expr_unary(token, TK_Increment, parse_expr(prefix_bp.right)); break;
         case TK_Decrement: left = ast_expr_unary(token, TK_Decrement, parse_expr(prefix_bp.right)); break;
+        case TK_Dereference: left = ast_expr_unary(token, TK_Dereference, parse_expr(prefix_bp.right)); break;
 
+        // Pointer typespec
+        case TK_Pointer: {
+            left = ast_expr_unary(token, TK_Pointer, parse_expr(prefix_bp.right));
+            auto unary = (Ast_Unary *)left;
+            propagate_polymorphic(unary, unary->expr);
+        } break;
+
+        // Array typespec
         case TK_OpenBracket: {
             Ast_Expr *expr = 0;
             if (!token_is(TK_CloseBracket))
@@ -608,14 +627,17 @@ parse_expr(S64 min_bp) {
             Ast_Array *result = ast_array(token, expr);
             token_expect(TK_CloseBracket);
             result->base = parse_expr(prefix_bp.right);
+            propagate_polymorphic(result, result->base);
             left = result;
         } break;
 
+        // Compound expression
         case TK_OpenBrace: {
             left = parse_expr_call(0, TK_CloseBrace);
             left->kind = AST_COMPOUND;
         } break;
 
+        // True, False
         case TK_Keyword: {
             if (token->intern_val == pctx->keyword_true)
                 left = ast_bool(token, 1);
@@ -695,8 +717,18 @@ CORE_Static Ast_Decl *
 parse_struct(Token *pos, Ast_Kind kind) {
     Scratch_Scope scratch(pctx->scratch);
 
-    token_match(OPEN_SCOPE);
+    Array<Ast_Decl *> params = {};
+    if (token_match(TK_OpenParen)) {
+        params = parse_parameter_list(scratch.arena);
+        For(params) {
+            if (!is_flag_set(it->flags, AST_POLYMORPH)) {
+                compiler_error(it->pos, "All struct arguments are required to be polymorphic");
+            }
+        }
+    }
+
     Ast_Scope *scope = begin_decl_scope(scratch.arena, token_get());
+    token_match(OPEN_SCOPE);
     do {
         Token *token = token_expect(TK_Identifier);
         token_expect(TK_Colon);
@@ -711,7 +743,7 @@ parse_struct(Token *pos, Ast_Kind kind) {
     token_expect(CLOSE_SCOPE);
 
     finalize_decl_scope(scope);
-    Ast_Decl *result = ast_struct(pos, scope, kind);
+    Ast_Decl *result = ast_struct(pos, scope, kind, params);
     return result;
 }
 
diff --git a/core_typechecking.cpp b/core_typechecking.cpp
index f10547b..efc2b90 100644
--- a/core_typechecking.cpp
+++ b/core_typechecking.cpp
@@ -1141,6 +1141,10 @@ resolve_expr(Ast_Expr *ast, Resolve_Flag flags, Ast_Type *compound_and_const_str
             Ast_Scope *scope = field_access_scope ? field_access_scope : node->parent_scope;
             Search_Flag flag = field_access_scope ? SEARCH_ONLY_CURRENT_SCOPE : 0;
 
+            if (!string_compare(ast->pos->file.s, "Language.core"_s)) { // @debug
+                int a = 10;
+            }
+
             Ast_Decl *decl = resolve_name(scope, node->pos, node->intern_val, flag | RESOLVE_NAME_MAKE_SURE_OPERATOR_OVERLOAD_IS_NOT_EVER_CALLED);
 
             // Substitute lambda alias
diff --git a/examples/polymorphism.core b/examples/polymorphism.core
index 11e9eb5..2694134 100644
--- a/examples/polymorphism.core
+++ b/examples/polymorphism.core
@@ -5,11 +5,6 @@ PushStruct :: (a: *MA.Arena, $T: Type): *$T
 	result := PushSize(a, size)
 	return result
 
-Array :: struct($T: Type)
-	data: *T
-	len: int
-	cap: int
-
 Array(int)
 
 QueueAddSLL(list: $List, node: $Node, first: #Identifier = first, last: #Identifier = last, next: #Identifier = next)
@@ -24,6 +19,10 @@ QueueAddSLL(list: $List, node: $Node, $first = first, $last = last, $next = next
 
 */
 
+Array :: struct($T: Type)
+	data: *T
+	len: int
+	cap: int
+
 main :: (argc: int, argv: **char): int
-	$i := 10
 	return 0
\ No newline at end of file