diff --git a/compiler/check/checker.ts b/compiler/check/checker.ts
index 01d9491..c156d2d 100644
--- a/compiler/check/checker.ts
+++ b/compiler/check/checker.ts
@@ -1,15 +1,16 @@
 import * as ast from "../ast/mod.ts";
 import { Ctx, File } from "../ctx.ts";
 import { Span } from "../diagnostics.ts";
+import { AstId, IdMap } from "../ids.ts";
 import { Resols } from "../resolve/resolver.ts";
 import { tyToString } from "../ty/to_string.ts";
 import { Ty } from "../ty/ty.ts";
 import { exhausted, Res, todo } from "../util.ts";
 
 export class Checker {
-    private itemTys = new Map<number, Ty>();
-    private exprTys = new Map<number, Ty>();
-    private tyTys = new Map<number, Ty>();
+    private itemTys = new IdMap<AstId, Ty>();
+    private exprTys = new IdMap<AstId, Ty>();
+    private tyTys = new IdMap<AstId, Ty>();
 
     private currentFile: File;
 
diff --git a/compiler/ctx.ts b/compiler/ctx.ts
index 6072567..e53e5b6 100644
--- a/compiler/ctx.ts
+++ b/compiler/ctx.ts
@@ -6,7 +6,8 @@ import {
     Report,
     Span,
 } from "./diagnostics.ts";
-import { File, IdentId, IdMap, Ids } from "./ids.ts";
+import { DefId, File, IdentId, IdMap, Ids } from "./ids.ts";
+export { type File } from "./ids.ts";
 
 export class Ctx {
     private fileIds = new Ids<File>();
@@ -105,10 +106,6 @@ export class Ctx {
 
     //
 
-    private defIds = new Ids<DefId>();
-
-    //
-
     public report(rep: Report) {
         this.reports.push(rep);
         this.reportImmediately(rep);
diff --git a/compiler/main.ts b/compiler/main.ts
index 4844f9c..b113337 100644
--- a/compiler/main.ts
+++ b/compiler/main.ts
@@ -1,8 +1,7 @@
 import * as path from "jsr:@std/path";
 import { Parser } from "./parse/parser.ts";
 import * as ast from "./ast/mod.ts";
-import { Ctx } from "./ctx.ts";
-import { File } from "./ctx.ts";
+import { Ctx, File } from "./ctx.ts";
 import { Resolver } from "./resolve/resolver.ts";
 import { Checker } from "./check/checker.ts";
 
diff --git a/compiler/parse/lexer.ts b/compiler/parse/lexer.ts
index 3c7e390..019e8ca 100644
--- a/compiler/parse/lexer.ts
+++ b/compiler/parse/lexer.ts
@@ -1,5 +1,6 @@
-import { Ctx, File } from "../ctx.ts";
+import { Ctx } from "../ctx.ts";
 import { Pos, Span } from "../diagnostics.ts";
+import { File } from "../ids.ts";
 import { ControlFlow, range } from "../util.ts";
 import { Token, TokenIter } from "./token.ts";
 
diff --git a/compiler/parse/token.ts b/compiler/parse/token.ts
index f7a26a5..3efbf69 100644
--- a/compiler/parse/token.ts
+++ b/compiler/parse/token.ts
@@ -1,5 +1,5 @@
-import { IdentId } from "../ctx.ts";
 import { Span } from "../diagnostics.ts";
+import { IdentId } from "../ids.ts";
 
 export type Token = {
     type: string;
diff --git a/compiler/resolve/cx.ts b/compiler/resolve/cx.ts
index 5ed2834..1fb3c65 100644
--- a/compiler/resolve/cx.ts
+++ b/compiler/resolve/cx.ts
@@ -1,5 +1,5 @@
 import * as ast from "../ast/mod.ts";
-import { IdentId, idKey, Key } from "../ctx.ts";
+import { IdentId, IdMap } from "../ids.ts";
 import { Res } from "../util.ts";
 
 export interface Syms {
@@ -30,17 +30,17 @@ export type Redef = {
 };
 
 export class SymsOneNsTab {
-    private defs = new Map<Key<IdentId>, Resolve>();
+    private defs = new IdMap<IdentId, Resolve>();
 
     public get(ident: ast.Ident): Resolve | undefined {
-        return this.defs.get(idKey(ident.id))!;
+        return this.defs.get(ident.id)!;
     }
 
     public def(ident: ast.Ident, kind: ResolveKind): Res<void, Redef> {
-        if (this.defs.has(idKey(ident.id))) {
-            return Res.Err({ ident: this.defs.get(idKey(ident.id))!.ident });
+        if (this.defs.has(ident.id)) {
+            return Res.Err({ ident: this.defs.get(ident.id)!.ident });
         }
-        this.defs.set(idKey(ident.id), { ident, kind });
+        this.defs.set(ident.id, { ident, kind });
         return Res.Ok(undefined);
     }
 }
@@ -127,4 +127,3 @@ export class LocalSyms implements Syms {
         return this.syms.defTy(ident, kind);
     }
 }
-
diff --git a/compiler/resolve/resolver.ts b/compiler/resolve/resolver.ts
index 637fa3d..4437dd8 100644
--- a/compiler/resolve/resolver.ts
+++ b/compiler/resolve/resolver.ts
@@ -1,5 +1,6 @@
 import * as ast from "../ast/mod.ts";
 import { Ctx, File } from "../ctx.ts";
+import { AstId, IdMap } from "../ids.ts";
 import { exhausted, todo } from "../util.ts";
 import {
     FnSyms,
@@ -12,10 +13,10 @@ import {
 
 export class Resols {
     public constructor(
-        private exprResols: Map<number, Resolve>,
+        private exprResols: IdMap<AstId, Resolve>,
     ) {}
 
-    public exprRes(id: number): Resolve {
+    public exprRes(id: AstId): Resolve {
         if (!this.exprResols.has(id)) {
             throw new Error();
         }
@@ -28,7 +29,7 @@ export class Resolver implements ast.Visitor {
     private rootSyms = new RootSyms();
     private syms: Syms = this.rootSyms;
 
-    private exprResols = new Map<number, Resolve>();
+    private exprResols = new IdMap<AstId, Resolve>();
 
     public constructor(
         private ctx: Ctx,