diff --git a/src/ast.ts b/src/ast.ts
index 831cabd..24086fc 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -5,6 +5,7 @@ export type Ast = {
   rootItems: Item[];
   typeckResults?: TypeckResults;
   itemsById: Map<ItemId, Item>;
+  packageName: string;
 };
 
 export type Identifier = {
@@ -36,6 +37,7 @@ export type ItemKind =
 export type Item = ItemKind & {
   span: Span;
   id: ItemId;
+  defPath?: string[];
 };
 
 export type FunctionDef = {
@@ -493,6 +495,7 @@ export function foldAst(ast: Ast, folder: Folder): Ast {
     rootItems: ast.rootItems.map((item) => folder.item(item)),
     itemsById: ast.itemsById,
     typeckResults: ast.typeckResults,
+    packageName: ast.packageName,
   };
 }
 
diff --git a/src/index.ts b/src/index.ts
index 8b5dadd..3225dfa 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,5 @@
 import { withErrorHandler } from "./error";
-import { tokenize } from "./lexer";
+import { isValidIdent, tokenize } from "./lexer";
 import { lower as lowerToWasm } from "./lower";
 import { parse } from "./parser";
 import { printAst } from "./printer";
@@ -7,28 +7,50 @@ import { resolve } from "./resolve";
 import { typeck } from "./typeck";
 import { writeModuleWatToString } from "./wasm/wat";
 import fs from "fs";
+import path from "path";
 import { exec } from "child_process";
 
 const INPUT = `
 function main() = (
-  owo.uwu.meow();
+  owo.uwu.main();
+  owo.owo();
 );
 
 mod owo (
   mod uwu (
-    function meow() =;
+    function main() =;
   );
+  function owo() = ;
 );
 `;
 
 function main() {
   let input: string;
+  let packageName: string;
   if (process.argv.length > 2) {
-    input = fs.readFileSync(process.argv[2], { encoding: "utf-8" });
+    const filename = process.argv[2];
+    if (path.extname(filename) !== ".nil") {
+      console.error(
+        `error: filename must have \`.nil\` extension: \`${filename}\``
+      );
+      process.exit(1);
+    }
+
+    input = fs.readFileSync(filename, { encoding: "utf-8" });
+    packageName = path.basename(filename, ".nil");
   } else {
     input = INPUT;
+    packageName = "test";
   }
 
+  if (!isValidIdent(packageName)) {
+    console.error(`error: package name \`${packageName}\` is not a valid identifer`);
+    process.exit(1);
+  }
+
+  console.log(`package name: '${packageName}'`);
+  
+
   withErrorHandler(input, () => {
     const start = Date.now();
 
@@ -36,7 +58,7 @@ function main() {
     console.log("-----TOKENS------------");
     console.log(tokens);
 
-    const ast = parse(tokens);
+    const ast = parse(packageName, tokens);
     console.log("-----AST---------------");
 
     console.dir(ast.rootItems, { depth: 50 });
diff --git a/src/lexer.ts b/src/lexer.ts
index a51d7ad..dfcdf99 100644
--- a/src/lexer.ts
+++ b/src/lexer.ts
@@ -272,6 +272,19 @@ export function tokenize(input: string): Token[] {
   return tokens;
 }
 
+export function isValidIdent(ident: string): boolean {
+  if (!isIdentStart(ident[0])) {
+    return false;
+  }
+  for (let i = 1; i < ident.length; i++) {
+    const char = ident[i];
+    if (!isIdentContinue(char)) {
+      return false;
+    }
+  }
+  return true;
+}
+
 function isIdentStart(char: string): boolean {
   return (
     (char <= "Z" && char >= "A") || (char <= "z" && char >= "a") || char === "_"
diff --git a/src/lower.ts b/src/lower.ts
index f3ebceb..e7fade7 100644
--- a/src/lower.ts
+++ b/src/lower.ts
@@ -12,7 +12,7 @@ import {
   TyTuple,
   varUnreachable,
 } from "./ast";
-import { encodeUtf8, unwrap } from "./utils";
+import { ComplexMap, encodeUtf8, unwrap } from "./utils";
 import * as wasm from "./wasm/defs";
 
 const USIZE: wasm.ValType = "i32";
@@ -29,43 +29,37 @@ type Relocation = {
   instr: wasm.Instr & { func: wasm.FuncIdx };
 } & { res: Resolution };
 
-type StringifiedMap<K, V> = { _map: Map<string, V> };
-
-function setMap<K, V>(map: StringifiedMap<K, V>, key: K, value: V) {
-  map._map.set(JSON.stringify(key), value);
-}
-
-function getMap<K, V>(map: StringifiedMap<K, V>, key: K): V | undefined {
-  return map._map.get(JSON.stringify(key));
-}
-
 type FuncOrImport =
   | { kind: "func"; idx: wasm.FuncIdx }
   | { kind: "import"; idx: number };
 
 export type Context = {
   mod: wasm.Module;
-  funcTypes: StringifiedMap<wasm.FuncType, wasm.TypeIdx>;
+  funcTypes: ComplexMap<wasm.FuncType, wasm.TypeIdx>;
   reservedHeapMemoryStart: number;
-  funcIndices: StringifiedMap<Resolution, FuncOrImport>;
+  funcIndices: ComplexMap<Resolution, FuncOrImport>;
   ast: Ast;
   relocations: Relocation[];
 };
 
+function mangleDefPath(defPath: string[]): string {
+  return `nil__${defPath.map(escapeIdentName).join("__")}`;
+}
+
 function escapeIdentName(name: string): string {
   // This allows the implementation to use 2 leading underscores
-  // for any names and it will not conflict.
-  return name.startsWith("__") ? `_${name}` : name;
+  // to separate ident parts of in a loading position and avoid conflicts.
+  return name.replace(/__/g, "___");
 }
 
 function internFuncType(cx: Context, type: wasm.FuncType): wasm.TypeIdx {
-  const existing = getMap(cx.funcTypes, type);
+  const existing = cx.funcTypes.get(type);
   if (existing !== undefined) {
     return existing;
   }
   const idx = cx.mod.types.length;
   cx.mod.types.push(type);
-  setMap(cx.funcTypes, type, idx);
+  cx.funcTypes.set(type, idx);
   return idx;
 }
 
@@ -121,25 +115,34 @@ export function lower(ast: Ast): wasm.Module {
 
   const cx: Context = {
     mod,
-    funcTypes: { _map: new Map() },
-    funcIndices: { _map: new Map() },
+    funcTypes: new ComplexMap(),
+    funcIndices: new ComplexMap(),
     reservedHeapMemoryStart: 0,
     ast,
     relocations: [],
   };
 
-  ast.rootItems.forEach((item) => {
-    switch (item.kind) {
-      case "function": {
-        lowerFunc(cx, item, item.node);
-        break;
+  function lowerMod(items: Item[]) {
+    items.forEach((item) => {
+      switch (item.kind) {
+        case "function": {
+          lowerFunc(cx, item, item.node);
+          break;
+        }
+        case "import": {
+          lowerImport(cx, item, item.node);
+          break;
+        }
+        case "mod": {
+          if (item.node.modKind.kind === "inline") {
+            lowerMod(item.node.modKind.contents);
+          }
+        }
       }
-      case "import": {
-        lowerImport(cx, item, item.node);
-        break;
-      }
-    }
-  });
+    });
+  }
+
+  lowerMod(ast.rootItems);
 
   const HEAP_ALIGN = 0x08;
   cx.reservedHeapMemoryStart =
@@ -154,7 +157,7 @@ export function lower(ast: Ast): wasm.Module {
   cx.relocations.forEach((rel) => {
     switch (rel.kind) {
       case "funccall": {
-        const idx = getMap<Resolution, FuncOrImport>(cx.funcIndices, rel.res);
+        const idx = cx.funcIndices.get(rel.res);
         if (idx === undefined) {
           throw new Error(
             `no function found for relocation '${JSON.stringify(rel.res)}'`
@@ -193,11 +196,7 @@ function lowerImport(cx: Context, item: Item, def: ImportDef) {
     });
   }
 
-  setMap<Resolution, FuncOrImport>(
-    cx.funcIndices,
-    { kind: "item", id: item.id },
-    { kind: "import", idx }
-  );
+  cx.funcIndices.set({ kind: "item", id: item.id }, { kind: "import", idx });
 }
 
 type FuncContext = {
@@ -223,7 +222,7 @@ function lowerFunc(cx: Context, item: Item, func: FunctionDef) {
   const type = internFuncType(cx, wasmType);
 
   const wasmFunc: wasm.Func = {
-    _name: escapeIdentName(func.name),
+    _name: mangleDefPath(item.defPath!),
     type,
     locals: [],
     body: [],
@@ -244,8 +243,8 @@ function lowerFunc(cx: Context, item: Item, func: FunctionDef) {
 
   const idx = fcx.cx.mod.funcs.length;
   fcx.cx.mod.funcs.push(wasmFunc);
-  setMap<Resolution, FuncOrImport>(
-    fcx.cx.funcIndices,
+
+  fcx.cx.funcIndices.set(
     { kind: "item", id: fcx.item.id },
     { kind: "func", idx }
   );
@@ -353,8 +352,10 @@ function lowerExpr(fcx: FuncContext, instrs: wasm.Instr[], expr: Expr) {
       }
       break;
     }
+    case "path":
     case "ident": {
-      const res = expr.value.res!;
+      const res = expr.kind === "ident" ? expr.value.res! : expr.res;
+
       switch (res.kind) {
         case "local": {
           const location =
@@ -382,9 +383,6 @@ function lowerExpr(fcx: FuncContext, instrs: wasm.Instr[], expr: Expr) {
 
       break;
     }
-    case "path": {
-      todo("path");
-    }
     case "binary": {
       // By evaluating the LHS first, the RHS is on top, which
       // is correct as it's popped first. Evaluating the LHS first
@@ -498,12 +496,15 @@ function lowerExpr(fcx: FuncContext, instrs: wasm.Instr[], expr: Expr) {
       break;
     }
     case "call": {
-      if (expr.lhs.kind !== "ident") {
+      if (expr.lhs.kind !== "ident" && expr.lhs.kind !== "path") {
         todo("non constant calls");
       }
 
-      if (expr.lhs.value.res!.kind === "builtin") {
-        switch (expr.lhs.value.res!.name) {
+      const res =
+        expr.lhs.kind === "ident" ? expr.lhs.value.res! : expr.lhs.res;
+
+      if (res.kind === "builtin") {
+        switch (res.name) {
           case "trap": {
             instrs.push({ kind: "unreachable" });
             break exprKind;
@@ -553,7 +554,7 @@ function lowerExpr(fcx: FuncContext, instrs: wasm.Instr[], expr: Expr) {
       fcx.cx.relocations.push({
         kind: "funccall",
         instr: callInstr,
-        res: expr.lhs.value.res!,
+        res,
       });
 
       expr.args.forEach((arg) => {
@@ -893,7 +894,7 @@ function addRt(cx: Context, ast: Ast) {
   const iovecArray = reserveMemory(8);
 
   const print: wasm.Func = {
-    _name: "___print",
+    _name: "nil__print",
     locals: [],
     type: internFuncType(cx, { params: [POINTER, USIZE], returns: [] }),
     body: [
@@ -917,8 +918,7 @@ function addRt(cx: Context, ast: Ast) {
   const printIdx = cx.mod.funcs.length;
   cx.mod.funcs.push(print);
 
-  setMap(
-    cx.funcIndices,
+  cx.funcIndices.set(
     { kind: "builtin", name: "print" },
     { kind: "func", idx: printIdx }
   );
diff --git a/src/parser.ts b/src/parser.ts
index 3bf1834..4f7a5fb 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -32,7 +32,7 @@ import { Ids } from "./utils";
 
 type Parser<T> = (t: Token[]) => [Token[], T];
 
-export function parse(t: Token[]): Ast {
+export function parse(packageName: string, t: Token[]): Ast {
   const items: Item[] = [];
 
   while (t.length > 0) {
@@ -41,7 +41,7 @@ export function parse(t: Token[]): Ast {
     items.push(item);
   }
 
-  const ast = assignIds(items);
+  const ast = buildAst(packageName, items);
 
   validateAst(ast);
 
@@ -711,13 +711,14 @@ function validateAst(ast: Ast) {
   foldAst(ast, validator);
 }
 
-function assignIds(rootItems: Item[]): Ast {
+function buildAst(packageName: string, rootItems: Item[]): Ast {
   const itemId = new Ids();
   const loopId = new Ids();
 
   const ast: Ast = {
     rootItems,
     itemsById: new Map(),
+    packageName,
   };
 
   const assigner: Folder = {
diff --git a/src/resolve.ts b/src/resolve.ts
index 20377b5..acc7596 100644
--- a/src/resolve.ts
+++ b/src/resolve.ts
@@ -39,7 +39,7 @@ function resolveModItem(
     case "inline": {
       const contents = new Map(
         mod.modKind.contents.map((item) => [item.node.name, item.id])
-      );      
+      );
       cx.modContentsCache.set(modId, contents);
       return contents.get(name);
     }
@@ -52,11 +52,15 @@ function resolveModItem(
 export function resolve(ast: Ast): Ast {
   const cx: Context = { ast, modContentsCache: new Map() };
 
-  const rootItems = resolveModule(cx, ast.rootItems);
+  const rootItems = resolveModule(cx, [ast.packageName], ast.rootItems);
   return { ...ast, rootItems };
 }
 
-function resolveModule(cx: Context, contents: Item[]): Item[] {
+function resolveModule(
+  cx: Context,
+  modName: string[],
+  contents: Item[]
+): Item[] {
   const items = new Map<string, number>();
 
   contents.forEach((item) => {
@@ -117,6 +121,8 @@ function resolveModule(cx: Context, contents: Item[]): Item[] {
       return cx.ast;
     },
     itemInner(item) {
+      const defPath = [...modName, item.node.name];
+
       switch (item.kind) {
         case "function": {
           const params = item.node.params.map(({ name, span, type }) => ({
@@ -143,22 +149,28 @@ function resolveModule(cx: Context, contents: Item[]): Item[] {
               body,
             },
             id: item.id,
+            defPath,
           };
         }
         case "mod": {
           if (item.node.modKind.kind === "inline") {
-            const contents = resolveModule(cx, item.node.modKind.contents);
+            const contents = resolveModule(
+              cx,
+              defPath,
+              item.node.modKind.contents
+            );
             return {
               ...item,
               kind: "mod",
               node: { ...item.node, modKind: { kind: "inline", contents } },
+              defPath,
             };
           }
           break;
         }
       }
 
-      return superFoldItem(item, this);
+      return { ...superFoldItem(item, this), defPath };
     },
     expr(expr) {
       switch (expr.kind) {
@@ -195,9 +207,16 @@ function resolveModule(cx: Context, contents: Item[]): Item[] {
           };
         }
         case "fieldAccess": {
-          if (expr.lhs.kind === "ident") {
-            // If the lhs is a module we need to convert this into a path.
-            const res = resolveIdent(expr.lhs.value);
+          // We convert field accesses to paths if the lhs refers to a module.
+
+          const lhs = this.expr(expr.lhs);
+
+          if (lhs.kind === "ident" || lhs.kind === "path") {
+            const res =
+              lhs.kind === "ident" ? resolveIdent(lhs.value) : lhs.res;
+            const segments =
+              lhs.kind === "ident" ? [lhs.value.name] : lhs.segments;
+
             if (res.kind === "item") {
               const module = unwrap(cx.ast.itemsById.get(res.id));
               if (module.kind === "mod") {
@@ -225,9 +244,9 @@ function resolveModule(cx: Context, contents: Item[]): Item[] {
 
                 return {
                   kind: "path",
-                  segments: [expr.lhs.value.name, expr.field.value],
+                  segments: [...segments, expr.field.value],
                   res: pathRes,
-                  span: spanMerge(expr.lhs.span, expr.field.span),
+                  span: spanMerge(lhs.span, expr.field.span),
                 };
               }
             }
diff --git a/src/utils.ts b/src/utils.ts
index 7bad492..f8be4fc 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -16,3 +16,26 @@ export function unwrap<T>(value: T | undefined): T {
   }
   return value;
 }
+
+/**
+ * A `Map` that can have arbitrarily complex keys.
+ * It uses JSON+string equality instead of refernece equality.
+ */
+export class ComplexMap<K, V> {
+  inner: Map<string | number, V> = new Map();
+
+  public get(key: K): V | undefined {
+    return this.inner.get(this.mangleKey(key));
+  }
+
+  public set(key: K, value: V) {
+    this.inner.set(this.mangleKey(key), value);
+  }
+
+  private mangleKey(key: K): string | number {
+    if (typeof key === "string" || typeof key === "number") {
+      return key;
+    }
+    return JSON.stringify(key);
+  }
+}
diff --git a/src/wasm/wat.ts b/src/wasm/wat.ts
index 48dc5d6..ba00a47 100644
--- a/src/wasm/wat.ts
+++ b/src/wasm/wat.ts
@@ -26,19 +26,21 @@ import {
 
 const identity = (s: string) => s;
 
-class Formatter {
+class FmtCtx {
   print: (chunk: string) => void;
   indentation: number;
   wordsInSexpr: number[];
   freshLinebreak: boolean;
   color: boolean;
+  mod: Module;
 
-  constructor(print: (chunk: string) => void, color = true) {
+  constructor(print: (chunk: string) => void, mod: Module, color = true) {
     this.print = print;
     this.indentation = 0;
     this.wordsInSexpr = [];
     this.freshLinebreak = false;
     this.color = color;
+    this.mod = mod;
   }
 
   linebreak() {
@@ -103,6 +105,10 @@ class Formatter {
     this.wordsInSexpr[last]++;
   }
 
+  comment(content: string | number) {
+    this.word(`(;${content};)`, chalk.gray);
+  }
+
   startSexpr() {
     this.word("(");
     this.wordsInSexpr.push(0);
@@ -121,21 +127,18 @@ class Formatter {
 export function writeModuleWatToString(module: Module, color = false): string {
   const parts: string[] = [];
   const writer = (s: string) => parts.push(s);
-  printModule(module, new Formatter(writer, color));
+  printModule(module, new FmtCtx(writer, module, color));
   return parts.join("");
 }
 
-export function writeModuleWat(module: Module, f: Formatter) {
-  printModule(module, f);
-}
 // base
 
-function printString(s: string, f: Formatter) {
+function printString(s: string, f: FmtCtx) {
   // TODO: escaping
   f.word(`"${s}"`);
 }
 
-function printBinaryString(buf: Uint8Array, f: Formatter) {
+function printBinaryString(buf: Uint8Array, f: FmtCtx) {
   const parts: string[] = [];
   for (let i = 0; i < buf.length; i++) {
     const byte = buf[i];
@@ -151,7 +154,7 @@ function printBinaryString(buf: Uint8Array, f: Formatter) {
   f.word(`"${parts.join("")}"`);
 }
 
-function printId(id: string | undefined, f: Formatter) {
+function printId(id: string | undefined, f: FmtCtx) {
   if (id) {
     f.word(`$${id}`);
   }
@@ -159,11 +162,11 @@ function printId(id: string | undefined, f: Formatter) {
 
 // types
 
-function printValType(type: ValType, f: Formatter) {
+function printValType(type: ValType, f: FmtCtx) {
   f.type(type);
 }
 
-function printFuncType(type: FuncType, f: Formatter) {
+function printFuncType(type: FuncType, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("func");
     f.sexpr(() => {
@@ -177,17 +180,17 @@ function printFuncType(type: FuncType, f: Formatter) {
   });
 }
 
-function printLimits(limits: Limits, f: Formatter) {
+function printLimits(limits: Limits, f: FmtCtx) {
   f.word(limits.min);
   f.word(limits.max);
 }
 
-function printTableType(type: TableType, f: Formatter) {
+function printTableType(type: TableType, f: FmtCtx) {
   printLimits(type.limits, f);
   printValType(type.reftype, f);
 }
 
-function printGlobalType(type: GlobalType, f: Formatter) {
+function printGlobalType(type: GlobalType, f: FmtCtx) {
   if (type.mut === "const") {
     printValType(type.type, f);
   } else {
@@ -200,7 +203,7 @@ function printGlobalType(type: GlobalType, f: Formatter) {
 
 // instrs
 
-function printBlockType(type: Blocktype, f: Formatter) {
+function printBlockType(type: Blocktype, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("type");
     if (type.kind === "typeidx") {
@@ -211,7 +214,7 @@ function printBlockType(type: Blocktype, f: Formatter) {
   });
 }
 
-function printMemarg(arg: MemArg, f: Formatter) {
+function printMemarg(arg: MemArg, f: FmtCtx) {
   if (arg.offset /*0->false*/) {
     f.word(`offset=${arg.offset}`);
   }
@@ -225,7 +228,7 @@ function printMemarg(arg: MemArg, f: Formatter) {
  * Start: indented start of first instr
  * End: start of next line
  */
-function printInstrBlock(instrs: Instr[], f: Formatter) {
+function printInstrBlock(instrs: Instr[], f: FmtCtx) {
   instrs.forEach((nested, i) => {
     printInstr(nested, f);
     if (i !== instrs.length - 1) {
@@ -235,7 +238,7 @@ function printInstrBlock(instrs: Instr[], f: Formatter) {
   f.breakDedent();
 }
 
-function printInstr(instr: Instr, f: Formatter) {
+function printInstr(instr: Instr, f: FmtCtx) {
   switch (instr.kind) {
     case "block":
     case "loop":
@@ -430,10 +433,15 @@ function printInstr(instr: Instr, f: Formatter) {
       instr.labels.forEach((label) => f.word(label));
       f.word(instr.label);
       break;
-    case "call":
+    case "call": {
       f.controlFlow(instr.kind);
       f.word(instr.func);
+      const name = f.mod.funcs[instr.func]?._name;
+      if (name) {
+        f.comment(name);
+      }
       break;
+    }
     case "call_indirect":
       f.controlFlow(instr.kind);
       f.word(instr.table);
@@ -504,14 +512,14 @@ function printInstr(instr: Instr, f: Formatter) {
 
 // modules
 
-function printType(type: FuncType, f: Formatter) {
+function printType(type: FuncType, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("type");
     printFuncType(type, f);
   });
 }
 
-function printImport(import_: Import, f: Formatter) {
+function printImport(import_: Import, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("import");
     printString(import_.module, f);
@@ -541,12 +549,12 @@ function printImport(import_: Import, f: Formatter) {
   });
 }
 
-function printFunction(func: Func, idx: number, f: Formatter) {
+function printFunction(func: Func, idx: number, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("func");
     printId(func._name, f);
 
-    f.word(`(;${idx};)`, chalk.gray);
+    f.comment(idx);
 
     f.sexpr(() => {
       f.keyword("type");
@@ -571,7 +579,7 @@ function printFunction(func: Func, idx: number, f: Formatter) {
   });
 }
 
-function printTable(table: Table, f: Formatter) {
+function printTable(table: Table, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("table");
     printId(table._name, f);
@@ -579,7 +587,7 @@ function printTable(table: Table, f: Formatter) {
   });
 }
 
-function printMem(mem: Mem, f: Formatter) {
+function printMem(mem: Mem, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("memory");
     printId(mem._name, f);
@@ -588,7 +596,7 @@ function printMem(mem: Mem, f: Formatter) {
   });
 }
 
-function printGlobal(global: Global, f: Formatter) {
+function printGlobal(global: Global, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("global");
     printId(global._name, f);
@@ -600,7 +608,7 @@ function printGlobal(global: Global, f: Formatter) {
   });
 }
 
-function printExport(export_: Export, f: Formatter) {
+function printExport(export_: Export, f: FmtCtx) {
   const desc = export_.desc;
 
   f.sexpr(() => {
@@ -614,18 +622,18 @@ function printExport(export_: Export, f: Formatter) {
   });
 }
 
-function printStart(start: Start, f: Formatter) {
+function printStart(start: Start, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("start");
     f.word(start.func);
   });
 }
 
-function printElem(_elem: Elem, f: Formatter) {
+function printElem(_elem: Elem, f: FmtCtx) {
   todo();
 }
 
-function printData(data: Data, f: Formatter) {
+function printData(data: Data, f: FmtCtx) {
   let mode = data.mode;
 
   f.sexpr(() => {
@@ -656,7 +664,7 @@ function printData(data: Data, f: Formatter) {
   });
 }
 
-function printModule(module: Module, f: Formatter) {
+function printModule(module: Module, f: FmtCtx) {
   f.sexpr(() => {
     f.keyword("module");
     printId(module._name, f);