diff --git a/src/front/check2.ts b/src/front/check2.ts
index 333b742..45f5d92 100644
--- a/src/front/check2.ts
+++ b/src/front/check2.ts
@@ -137,7 +137,7 @@ class TypeChecker {
                         break;
                     }
                     case "AssignStmt": {
-                        const placeTy = this.expr(k.place, Ty.Any);
+                        const placeTy = this.place(k.place, Ty.Any);
                         const exprTy = this.expr(k.expr, placeTy);
                         if (!placeTy.resolvableWith(exprTy)) {
                             this.reporter.error(
diff --git a/src/main.ts b/src/main.ts
index 4da6e30..2170d37 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -70,7 +70,7 @@ const fnTys = checker.checkFn(mainFn);
 //     },
 // });
 
-const m = new middle.MiddleLowerer(syms, tys);
+const m = new middle.MiddleLowerer(syms, checker);
 const mainMiddleFn = m.lowerFn(mainFn);
 
 if (Deno.args.includes("--print-mir")) {
diff --git a/src/middle.ts b/src/middle.ts
index 7339bf0..2834d68 100644
--- a/src/middle.ts
+++ b/src/middle.ts
@@ -1,5 +1,5 @@
 import * as ast from "./ast.ts";
-import { Syms, Tys } from "./front/mod.ts";
+import { CheckedFn, Checker, Syms, Tys } from "./front/mod.ts";
 import { Ty } from "./ty.ts";
 import { BasicBlock, BinaryOp, Fn, Inst, InstKind } from "./mir.ts";
 
@@ -8,14 +8,19 @@ export class MiddleLowerer {
 
     constructor(
         private syms: Syms,
-        private tys: Tys,
+        private checker: Checker,
     ) {}
 
     lowerFn(stmt: ast.FnStmt): Fn {
         if (this.fns.has(stmt.id)) {
             return this.fns.get(stmt.id)!;
         }
-        const fn = new FnLowerer(this, this.syms, this.tys, stmt).lower();
+        const fn = new FnLowerer(
+            this,
+            this.syms,
+            this.checker.checkFn(stmt),
+            stmt,
+        ).lower();
         this.fns.set(stmt.id, fn);
         return fn;
     }
@@ -34,12 +39,12 @@ class FnLowerer {
     constructor(
         private lowerer: MiddleLowerer,
         private syms: Syms,
-        private tys: Tys,
+        private tys: CheckedFn,
         private stmt: ast.FnStmt,
     ) {}
 
     lower(): Fn {
-        const ty = this.tys.fnStmt(this.stmt);
+        const ty = this.tys.ty();
         this.lowerBlock(this.stmt.kind.body.as("Block"));
         this.pushInst(Ty.Void, "Return", { source: this.makeVoid() });
         this.bbs[0].insts.unshift(...this.allocs);
@@ -172,7 +177,7 @@ class FnLowerer {
     }
 
     private lowerLetStmt(stmt: ast.NodeWithKind<"LetStmt">) {
-        const ty = this.tys.param(stmt.kind.param.as("Param"));
+        const ty = this.tys.exprTy(stmt.kind.expr);
         const expr = this.lowerExpr(stmt.kind.expr);
         const local = new Inst(
             Ty.create("PtrMut", { ty }),
@@ -195,7 +200,7 @@ class FnLowerer {
     private lowerPlace(place: ast.Node): Inst {
         // evaluate to most direct pointer
 
-        const _ty = this.tys.place(place);
+        const _ty = this.tys.exprTy(place);
 
         if (place.is("IdentExpr")) {
             const sym = this.syms.get(place);
@@ -218,9 +223,9 @@ class FnLowerer {
 
         if (place.is("IndexExpr")) {
             const value = place.kind.value;
-            const valueTy = this.tys.place(value);
+            const valueTy = this.tys.exprTy(value);
             const arg = place.kind.arg;
-            const argTy = this.tys.expr(arg);
+            const argTy = this.tys.exprTy(arg);
             if (valueTy.is("Array") || valueTy.is("Slice")) {
                 const valueInst = this.lowerPlace(place.kind.value);
                 if (argTy.is("Int")) {
@@ -257,7 +262,7 @@ class FnLowerer {
     }
 
     private lowerExpr(expr: ast.Node): Inst {
-        const ty = this.tys.expr(expr);
+        const ty = this.tys.exprTy(expr);
         if (expr.is("IdentExpr")) {
             const sym = this.syms.get(expr);
             if (sym.tag === "Fn") {
@@ -265,7 +270,9 @@ class FnLowerer {
                 return this.pushInst(fn.ty, "Fn", { fn });
             }
             if (sym.tag === "FnParam") {
-                const ty = this.tys.expr(sym.param);
+                const ty = this.tys.ty().as("FnStmt")
+                    .kind.ty.as("Fn")
+                    .kind.params[sym.idx];
                 return this.pushInst(ty, "Param", { idx: sym.idx });
             }
             if (sym.tag === "Builtin") {
@@ -290,7 +297,7 @@ class FnLowerer {
             return this.pushInst(ty, "Str", { value: expr.kind.value });
         }
         if (expr.is("ArrayExpr")) {
-            const ty = this.tys.expr(expr);
+            const ty = this.tys.exprTy(expr);
             const values = expr.kind.values
                 .map((value) => this.lowerExpr(value));
             return this.pushInst(ty, "Array", { values });
@@ -323,8 +330,8 @@ class FnLowerer {
             return this.lowerUnaryExpr(expr);
         }
         if (expr.is("BinaryExpr")) {
-            const leftTy = this.tys.expr(expr.kind.left);
-            const rightTy = this.tys.expr(expr.kind.right);
+            const leftTy = this.tys.exprTy(expr.kind.left);
+            const rightTy = this.tys.exprTy(expr.kind.right);
             const binaryOp = binaryOpTests
                 .map((test) => test(expr.kind.op, leftTy, rightTy, ty))
                 .filter((tested) => tested)
@@ -342,8 +349,8 @@ class FnLowerer {
     }
 
     private lowerUnaryExpr(expr: ast.NodeWithKind<"UnaryExpr">) {
-        const resultTy = this.tys.expr(expr);
-        const operandTy = this.tys.expr(expr.kind.expr);
+        const resultTy = this.tys.exprTy(expr);
+        const operandTy = this.tys.exprTy(expr.kind.expr);
         if (
             expr.kind.op === "Neg" &&
             operandTy.resolvableWith(Ty.I32) &&
@@ -376,7 +383,7 @@ class FnLowerer {
                 );
             }
             if (place.is("IndexExpr")) {
-                const placeTy = this.tys.expr(place);
+                const placeTy = this.tys.exprTy(place);
                 const placeInst = this.lowerPlace(place);
                 if (placeTy.is("Slice")) {
                     return placeInst;