diff --git a/src/ast.ts b/src/ast.ts
index cb5de7a..3120960 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -411,10 +411,6 @@ export type TypeKind<P extends Phase> =
       generics: Type<P>[];
       value: IdentWithRes<P>;
     }
-  | {
-      kind: "list";
-      elem: Type<P>;
-    }
   | {
       kind: "tuple";
       elems: Type<P>[];
@@ -517,11 +513,6 @@ export type TyBool = {
   kind: "bool";
 };
 
-export type TyList = {
-  kind: "list";
-  elem: Ty;
-};
-
 export type TyTuple = {
   kind: "tuple";
   elems: Ty[];
@@ -549,7 +540,7 @@ export type TyStruct = {
   params: string[];
   args: Ty[];
   _name: string;
-  fields: [string, Ty][];
+  fields_no_subst: [string, Ty][];
 };
 
 export type TyRawPtr = {
@@ -582,7 +573,6 @@ export type Ty =
   | TyInt
   | TyI32
   | TyBool
-  | TyList
   | TyTuple
   | TyFn
   | TyVar
@@ -607,6 +597,49 @@ export type TypeckResults = {
   main: Resolution | undefined;
 };
 
+export function structFieldsSubstituted(ty: TyStruct): [string, Ty][] {
+  const args = ty.args;
+  return ty.fields_no_subst.map(([name, type]) => [
+    name,
+    substituteTy(args, type),
+  ]);
+}
+
+// Substitute the parameter of a type. We are only able to handle one
+// level of generic definitions, for example for fields the struct def or for exprs the function generics.
+export function substituteTy(params: Ty[], ty: Ty): Ty {
+  const subst = (ty: Ty) => substituteTy(params, ty);
+
+  switch (ty.kind) {
+    case "param":
+      return params[ty.idx];
+    case "tuple":
+      return { ...ty, elems: ty.elems.map(subst) };
+    case "fn":
+      return {
+        ...ty,
+        returnTy: subst(ty.returnTy),
+        params: ty.params.map(subst),
+      };
+    case "struct":
+      return {
+        ...ty,
+        args: ty.args.map(subst),
+      };
+    case "rawptr":
+      return { ...ty, inner: subst(ty.inner) };
+    // Primitives
+    case "var":
+    case "string":
+    case "int":
+    case "i32":
+    case "bool":
+    case "never":
+    case "error":
+      return ty;
+  }
+}
+
 // folders
 
 export type FoldFn<From, To> = (value: From) => To;
@@ -894,13 +927,6 @@ export function superFoldType<From extends Phase, To extends Phase>(
         span,
       };
     }
-    case "list": {
-      return {
-        kind: "list",
-        elem: folder.type(type.elem),
-        span,
-      };
-    }
     case "tuple": {
       return {
         kind: "tuple",
diff --git a/src/codegen.test.ts b/src/codegen.test.ts
index 91015e1..3859ef3 100644
--- a/src/codegen.test.ts
+++ b/src/codegen.test.ts
@@ -8,7 +8,7 @@ it("should compute struct layout correctly", () => {
     args: [],
     params: [],
     _name: "",
-    fields: [
+    fields_no_subst: [
       ["uwu", TY_I32],
       ["owo", TY_INT],
     ],
@@ -55,7 +55,7 @@ it("should compute single field struct layout correctly", () => {
     args: [],
     params: [],
     _name: "",
-    fields: [["owo", TY_INT]],
+    fields_no_subst: [["owo", TY_INT]],
   };
 
   const layout = layoutOfStruct(ty);
diff --git a/src/codegen.ts b/src/codegen.ts
index 7e2a063..b6d5879 100644
--- a/src/codegen.ts
+++ b/src/codegen.ts
@@ -21,6 +21,7 @@ import {
   varUnreachable,
   TyRawPtr,
   paramUnreachable,
+  structFieldsSubstituted,
 } from "./ast";
 import { GlobalContext } from "./context";
 import { unreachable } from "./error";
@@ -1247,8 +1248,6 @@ function argRetAbi(param: Ty): ArgRetAbi {
       return ["i32"];
     case "bool":
       return ["i32"];
-    case "list":
-      todo("list abi");
     case "tuple":
       return param.elems.flatMap(argRetAbi);
     case "struct":
@@ -1304,8 +1303,6 @@ function wasmTypeForBody(ty: Ty): wasm.ValType[] {
       return ["i32"];
     case "bool":
       return ["i32"];
-    case "list":
-      todo("list types");
     case "tuple":
       return ty.elems.flatMap(wasmTypeForBody);
     case "fn":
@@ -1344,7 +1341,8 @@ export function layoutOfStruct(ty_: TyStruct | TyRawPtr): StructLayout {
   if (ty.kind !== "struct") {
     unreachable("must be struct");
   }
-  const fieldWasmTys = ty.fields.map(([, field]) => wasmTypeForBody(field));
+  const fieldTys = structFieldsSubstituted(ty).map(([_, ty]) => ty);
+  const fieldWasmTys = fieldTys.map((field) => wasmTypeForBody(field));
 
   // TODO: Use the max alignment instead.
   const align = fieldWasmTys.some((field) =>
@@ -1359,7 +1357,7 @@ export function layoutOfStruct(ty_: TyStruct | TyRawPtr): StructLayout {
   const fields: StructFieldLayout[] = fieldWasmTys.map((field, i) => {
     const value: StructFieldLayout = {
       types: [],
-      ty: ty.fields[i][1],
+      ty: fieldTys[i],
     };
 
     const types = field.map((type) => {
@@ -1457,8 +1455,6 @@ function needsRefcount(ty: Ty): StructLayout | "string" | undefined {
       return undefined;
     case "struct":
       return layoutOfStruct(ty);
-    case "list":
-      todo("no lists yet");
     case "var":
       varUnreachable();
     default:
diff --git a/src/parser.ts b/src/parser.ts
index 2ce727f..6824197 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -700,12 +700,6 @@ function parseType(t: State): [State, Type<Parsed>] {
         },
       ];
     }
-    case "[": {
-      let elem;
-      [t, elem] = parseType(t);
-      [t] = expectNext(t, "]");
-      return [t, { kind: "list", elem, span }];
-    }
     case "(": {
       // `()` is a the unit type, an empty tuple.
       // `(T)` is just `T`
diff --git a/src/printer.ts b/src/printer.ts
index d00544e..e6a4f0c 100644
--- a/src/printer.ts
+++ b/src/printer.ts
@@ -219,8 +219,6 @@ function printType(type: Type<AnyPhase>): string {
   switch (type.kind) {
     case "ident":
       return printIdent(type.value);
-    case "list":
-      return `[${printType(type.elem)}]`;
     case "tuple":
       return `(${type.elems.map(printType).join(", ")})`;
     case "rawptr":
@@ -269,9 +267,6 @@ export function printTy(ty: Ty): string {
     case "bool": {
       return "Bool";
     }
-    case "list": {
-      return `[${printTy(ty.elem)}]`;
-    }
     case "tuple": {
       return `(${ty.elems.map(printTy).join(", ")})`;
     }
diff --git a/src/typeck.ts b/src/typeck.ts
index 325cf35..9130bb4 100644
--- a/src/typeck.ts
+++ b/src/typeck.ts
@@ -183,12 +183,6 @@ function lowerAstTy(cx: TypeckCtx, type: Type<Resolved>): Ty {
 
       return ty;
     }
-    case "list": {
-      return {
-        kind: "list",
-        elem: lowerAstTy(cx, type.elem),
-      };
-    }
     case "tuple": {
       return {
         kind: "tuple",
@@ -286,7 +280,7 @@ function typeOfItem(cx: TypeckCtx, itemId: ItemId, cause: Span): Ty {
             params: item.generics.map((ident) => ident.name),
             itemId: item.id,
             _name: item.name,
-            fields: [
+            fields_no_subst: [
               /*dummy*/
             ],
           };
@@ -297,7 +291,7 @@ function typeOfItem(cx: TypeckCtx, itemId: ItemId, cause: Span): Ty {
             ({ name, type }) => [name.name, lowerAstTy(cx, type)],
           );
 
-          ty.fields = fields;
+          ty.fields_no_subst = fields;
           break;
         }
         case "alias": {
@@ -667,13 +661,6 @@ export class InferContext {
         if (rhs.kind === "bool") return;
         break;
       }
-      case "list": {
-        if (rhs.kind === "list") {
-          this.assign(lhs.elem, rhs.elem, span);
-          return;
-        }
-        break;
-      }
       case "tuple": {
         if (rhs.kind === "tuple" && lhs.elems.length === rhs.elems.length) {
           lhs.elems.forEach((lhs, i) => this.assign(lhs, rhs.elems[i], span));
@@ -953,7 +940,7 @@ export function checkBody(
             case "rawptr": {
               let fields: [string, Ty][];
               if (lhs.ty.kind === "struct") {
-                fields = lhs.ty.fields;
+                fields = lhs.ty.fields_no_subst;
               } else if (lhs.ty.kind === "rawptr") {
                 let inner = fcx.infcx.resolveIfPossible(lhs.ty.inner);
                 if (inner.kind !== "struct") {
@@ -967,7 +954,7 @@ export function checkBody(
                   ty = inner;
                   break;
                 } else {
-                  fields = inner.fields;
+                  fields = inner.fields_no_subst;
                 }
               } else {
                 fields = [];
@@ -1100,7 +1087,7 @@ export function checkBody(
           const assignedFields = new Set();
 
           fields.forEach(({ name, expr: field }, i) => {
-            const fieldIdx = structTy.fields.findIndex(
+            const fieldIdx = structTy.fields_no_subst.findIndex(
               (def) => def[0] === name.name,
             );
             if (fieldIdx == -1) {
@@ -1112,14 +1099,14 @@ export function checkBody(
                 ),
               );
             }
-            const fieldTy = structTy.fields[fieldIdx];
+            const fieldTy = structTy.fields_no_subst[fieldIdx];
             infcx.assign(fieldTy[1], field.ty, field.span);
             assignedFields.add(name.name);
             fields[i].fieldIdx = fieldIdx;
           });
 
           const missing: string[] = [];
-          structTy.fields.forEach(([name]) => {
+          structTy.fields_no_subst.forEach(([name]) => {
             if (!assignedFields.has(name)) {
               missing.push(name);
             }
diff --git a/test.nil b/test.nil
index 7b7c8d8..60472c9 100644
--- a/test.nil
+++ b/test.nil
@@ -1,4 +1,6 @@
-function main() = (
-  let list = std.list.new();
-  std.list.push(list, 0);
-);
\ No newline at end of file
+//@check-pass
+type A[T] = struct { a: T };
+
+function main() = ;
+
+function test(a: A[I32]) = ;
diff --git a/ui-tests/type/generics/codegen.nil b/ui-tests/type/generics/generics_structs_in_args.nil
similarity index 100%
rename from ui-tests/type/generics/codegen.nil
rename to ui-tests/type/generics/generics_structs_in_args.nil