diff --git a/src/front/check.ts b/src/front/check.ts
index be4b08a..ae7e67e 100644
--- a/src/front/check.ts
+++ b/src/front/check.ts
@@ -28,7 +28,7 @@ export class Tys {
         if (this.nodeTys.has(node.id)) {
             return this.nodeTys.get(node.id)!;
         }
-        const ty = this.checker.checkExpr(node);
+        const ty = this.checker.checkPlace(node);
         this.nodeTys.set(node.id, ty);
         return ty;
     }
@@ -82,6 +82,14 @@ class Checker {
     }
 
     checkPlace(node: ast.Node): Ty {
+        if (node.is("UnaryExpr")) {
+            if (node.kind.op === "Deref") {
+                const exprTy = this.checkPlace(node.kind.expr);
+                if (exprTy.is("Ptr") || exprTy.is("PtrMut")) {
+                    return exprTy.kind.ty;
+                }
+            }
+        }
         return this.checkExpr(node);
     }
 
@@ -157,7 +165,7 @@ class Checker {
         }
 
         if (node.is("IndexExpr")) {
-            const exprTy = this.tys.expr(node.kind.value);
+            const exprTy = this.tys.place(node.kind.value);
             const argTy = this.tys.expr(node.kind.arg);
             if (
                 (exprTy.is("Array") || exprTy.is("Slice")) &&
@@ -198,6 +206,13 @@ class Checker {
             }
             if (node.kind.op === "Deref") {
                 if (exprTy.is("Ptr") || exprTy.is("PtrMut")) {
+                    if (!exprTy.kind.ty.isSized()) {
+                        this.error(
+                            node.loc,
+                            `cannot dereference unsized type '${exprTy.kind.ty.pretty()}' in an expression`,
+                        );
+                        this.fail();
+                    }
                     return exprTy.kind.ty;
                 }
             }
diff --git a/src/front/parse.ts b/src/front/parse.ts
index 22a28cd..d2896ae 100644
--- a/src/front/parse.ts
+++ b/src/front/parse.ts
@@ -18,7 +18,7 @@ export class Parser {
         private text: string,
         private reporter: FileReporter,
     ) {
-        this.toks = tokenize(text);
+        this.toks = tokenize(this.text, this.reporter);
     }
 
     parseFile(): ast.Node {
@@ -402,7 +402,7 @@ const keywordPattern =
 const operatorPattern2 =
     /((?:\->)|(?:==)|(?:!=)|(?:<=)|(?:>=)|(?:<<)|(?:>>)|(?:\.\*)|(?:\.\.)|(?:\.\.=)|[\n\(\)\{\}\[\]\,\.\;\:\!\=\<\>\&\^\|\+\-\*\/\%])/g;
 
-export function tokenize(text: string): Tok[] {
+export function tokenize(text: string, reporter: FileReporter): Tok[] {
     return new Lexer()
         .add(/[ \t\r\n]+/, (_) => null)
         .add(/\/\/[^\n]*/, (_) => null)
@@ -415,6 +415,8 @@ export function tokenize(text: string): Tok[] {
             return { type: "int", value, loc };
         })
         .add(/./, (loc, value) => {
+            const escapedChar = JSON.stringify(value[0]).slice(1, -1);
+            reporter.error(loc, `illegal character '${escapedChar}'`);
             return null;
         })
         .lex(text);
diff --git a/src/main.ts b/src/main.ts
index 918627a..ecbbb17 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2,6 +2,7 @@ import * as ast from "./ast.ts";
 import { Reporter } from "./diagnostics.ts";
 import * as front from "./front/mod.ts";
 import * as middle from "./middle.ts";
+import * as mir from "./mir.ts";
 import { FnInterpreter } from "./mir_interpreter.ts";
 
 const reporter = new Reporter();
@@ -39,8 +40,56 @@ if (!mainFn) {
 const m = new middle.MiddleLowerer(syms, tys);
 const mainMiddleFn = m.lowerFn(mainFn);
 
-if (!Deno.args.includes("--test")) {
-    console.log(mainMiddleFn.pretty());
+function printMirFn(fn: mir.Fn) {
+    const pretty = fn.pretty();
+    const [lines, colors] = pretty
+        .split("\n")
+        .map<[string, string[]]>((line) => [line, []])
+        .map<[string, string[]]>(([line, colors]) => {
+            line = line.replace(/%(\d+)/g, "__%$1__");
+            if (/^\s*__%\d+__ \(.*?\) =/.test(line)) {
+                line = line.replace(
+                    /__%(\d+)__ \((.*?)\) =/g,
+                    "%c%$1 %c($2)%c =",
+                );
+                colors.push("color: lightblue;", "color: gray;", "");
+            }
+            if (/[A-Z][a-zA-Z]+/.test(line)) {
+                line = line.replace(/([A-Z][a-zA-Z]+)/, "%c$1%c");
+                colors.push("color: red;", "");
+            }
+            if (/\bptr\b/.test(line)) {
+                line = line.replace(/\b(ptr)\b/, "%c$1%c");
+                colors.push("color: gray;", "");
+            }
+            while (/__%\d+__/.test(line)) {
+                line = line.replace(/__%(\d+)__/, "%c%$1%c");
+                colors.push("color: lightblue;", "");
+            }
+
+            return [line, colors];
+        })
+        .reduce<[string[], string[]]>(
+            ([linesAcc, colorsAcc], [line, colors]) => {
+                linesAcc.push(line);
+                colorsAcc.push(...colors);
+                return [linesAcc, colorsAcc];
+            },
+            [[], []],
+        );
+    const text = lines.join("\n");
+    console.log(text + "%c", ...colors, "");
+}
+
+if (Deno.args.includes("--print-mir")) {
+    for (const fn of m.allFns()) {
+        printMirFn(fn);
+    }
+}
+
+if (!reporter.ok()) {
+    reporter.printAll();
+    Deno.exit(1);
 }
 
 new FnInterpreter(mainMiddleFn, []).eval();
diff --git a/src/middle.ts b/src/middle.ts
index b08df4e..5001ac6 100644
--- a/src/middle.ts
+++ b/src/middle.ts
@@ -19,6 +19,10 @@ export class MiddleLowerer {
         this.fns.set(stmt.id, fn);
         return fn;
     }
+
+    allFns(): Fn[] {
+        return this.fns.values().toArray();
+    }
 }
 
 class FnLowerer {
@@ -50,19 +54,7 @@ class FnLowerer {
 
     private lowerStmt(stmt: ast.Node) {
         if (stmt.is("LetStmt")) {
-            const ty = this.tys.expr(stmt.kind.param);
-            const expr = this.lowerExpr(stmt.kind.expr);
-            const local = new Inst(
-                Ty.create("PtrMut", { ty }),
-                { tag: "Alloca" },
-            );
-            this.allocs.push(local);
-            this.pushInst(Ty.Void, "Store", {
-                target: local,
-                source: expr,
-            });
-            this.localMap.set(stmt.kind.param.id, local);
-            return;
+            return this.lowerLetStmt(stmt);
         }
         if (stmt.is("ReturnStmt")) {
             const source = stmt.kind.expr
@@ -159,10 +151,7 @@ class FnLowerer {
             return;
         }
         if (stmt.is("AssignStmt")) {
-            const source = this.lowerExpr(stmt.kind.expr);
-            const target = this.lowerPlace(stmt.kind.place);
-            this.pushInst(Ty.Void, "Store", { target, source });
-            return;
+            return this.lowerAssignStmt(stmt);
         }
         if (stmt.is("ExprStmt")) {
             this.lowerExpr(stmt.kind.expr);
@@ -171,7 +160,30 @@ class FnLowerer {
         throw new Error(`'${stmt.kind.tag}' not handled`);
     }
 
+    private lowerLetStmt(stmt: ast.NodeWithKind<"LetStmt">) {
+        const ty = this.tys.expr(stmt.kind.param);
+        const expr = this.lowerExpr(stmt.kind.expr);
+        const local = new Inst(
+            Ty.create("PtrMut", { ty }),
+            { tag: "Alloca" },
+        );
+        this.allocs.push(local);
+        this.pushInst(Ty.Void, "Store", {
+            target: local,
+            source: expr,
+        });
+        this.localMap.set(stmt.kind.param.id, local);
+    }
+
+    private lowerAssignStmt(stmt: ast.NodeWithKind<"AssignStmt">) {
+        const source = this.lowerExpr(stmt.kind.expr);
+        const target = this.lowerPlace(stmt.kind.place);
+        this.pushInst(Ty.Void, "Store", { target, source });
+    }
+
     private lowerPlace(place: ast.Node): Inst {
+        // evaluate to most direct pointer
+
         const ty = this.tys.place(place);
         if (place.is("IdentExpr")) {
             const sym = this.syms.get(place);
@@ -189,17 +201,18 @@ class FnLowerer {
         }
 
         if (place.is("UnaryExpr") && place.kind.op === "Deref") {
-            const source = this.lowerPlace(place.kind.expr);
-            return this.pushInst(
-                Ty.create("PtrMut", { ty }),
-                "Load",
-                { source },
-            );
+            const source = this.lowerExpr(place.kind.expr);
+            // return this.pushInst(
+            //     Ty.create("PtrMut", { ty }),
+            //     "Load",
+            //     { source },
+            // );
+            return source;
         }
 
         if (place.is("IndexExpr")) {
             const value = place.kind.value;
-            const valueTy = this.tys.expr(value);
+            const valueTy = this.tys.place(value);
             const arg = place.kind.arg;
             const argTy = this.tys.expr(arg);
             if (!valueTy.is("Array") && !valueTy.is("Slice")) {
@@ -210,7 +223,7 @@ class FnLowerer {
                 const argInst = this.lowerExpr(arg);
                 return this.pushInst(
                     Ty.create("PtrMut", { ty: valueTy.kind.ty }),
-                    "Index",
+                    "GetElemPtr",
                     { base: valueInst, offset: argInst },
                 );
             }
diff --git a/src/mir.ts b/src/mir.ts
index 1ee4f5b..63d193e 100644
--- a/src/mir.ts
+++ b/src/mir.ts
@@ -100,7 +100,7 @@ export class Inst {
 
     pretty(cx: PrettyCx): string {
         const valueless = ["Store", "Jump", "Branch", "Return", "DebugPrint"];
-        const valueType = `%${cx.regId(this)} = ${this.ty.pretty()} `;
+        const valueType = `%${cx.regId(this)} (${this.ty.pretty()}) = `;
         return `${
             !valueless.includes(this.kind.tag) ? valueType : ""
         }${this.kind.tag} ${this.prettyArgs(cx)}`;
@@ -127,10 +127,10 @@ export class Inst {
                 return `${k.fn.stmt.kind.ident}`;
             case "Param":
                 return `${k.idx}`;
-            case "Index":
-                return `${r(k.base)} &[${r(k.offset)}]`;
+            case "GetElemPtr":
+                return `&[ptr ${r(k.base)}][${r(k.offset)}]`;
             case "Slice":
-                return `${r(k.value)} [${k.begin ? r(k.begin) : ""}..${
+                return `&[ptr ${r(k.value)}][${k.begin ? r(k.begin) : ""}..${
                     k.end ? r(k.end) : ""
                 }]`;
             case "Call":
@@ -138,9 +138,9 @@ export class Inst {
             case "Alloca":
                 return "";
             case "Load":
-                return `${r(k.source)}`;
+                return `[ptr ${r(k.source)}]`;
             case "Store":
-                return `${r(k.target)} = ${r(k.source)}`;
+                return `[ptr ${r(k.target)}] = ${r(k.source)}`;
             case "Jump":
                 return `bb${cx.bbId(k.target)}`;
             case "Branch":
@@ -184,7 +184,7 @@ export type InstKind =
     | { tag: "Array"; values: Inst[] }
     | { tag: "Fn"; fn: Fn }
     | { tag: "Param"; idx: number }
-    | { tag: "Index"; base: Inst; offset: Inst }
+    | { tag: "GetElemPtr"; base: Inst; offset: Inst }
     | { tag: "Slice"; value: Inst; begin: Inst | null; end: Inst | null }
     | { tag: "Call"; callee: Inst; args: Inst[] }
     | { tag: "Alloca" }
diff --git a/src/mir_interpreter.ts b/src/mir_interpreter.ts
index 9dbfadd..f54337c 100644
--- a/src/mir_interpreter.ts
+++ b/src/mir_interpreter.ts
@@ -13,12 +13,12 @@ export class FnInterpreter {
     }
 
     eval(): Val {
-        const cx = new mir.PrettyCx();
+        // const cx = new mir.PrettyCx();
         while (this.instIdx < this.bb.insts.length) {
             const inst = this.bb.insts[this.instIdx];
             this.instIdx += 1;
 
-            // console.log(poin
+            // console.log(
             //     `[${this.instIdx.toString().padStart(2, " ")}] ${
             //         inst.pretty(cx)
             //     }`,
@@ -50,45 +50,7 @@ export class FnInterpreter {
                 case "Param":
                     this.regs.set(inst, this.args[k.idx]);
                     break;
-                // case "Index": {
-                //     const idx = this.regs.get(k.arg)!;
-                //     if (idx.kind.tag !== "Int") {
-                //         throw new Error();
-                //     }
-                //     const value = this.regs.get(k.value)!;
-                //     if (value.kind.tag === "Array") {
-                //         if (idx.kind.value >= value.kind.values.length) {
-                //             throw new Error();
-                //         }
-                //         this.regs.set(inst, value.kind.values[idx.kind.value]);
-                //     } else if (value.kind.tag === "Slice") {
-                //         if (value.kind.value.kind.tag !== "Array") {
-                //             throw new Error();
-                //         }
-                //         const values = value.kind.value.kind.values;
-                //         const begin = value.kind.value;
-                //         const end = value.kind.end;
-                //         if (
-                //             begin.kind.tag !== "Int" || end.kind.tag !== "Int"
-                //         ) {
-                //             throw new Error();
-                //         }
-                //         if (
-                //             begin.kind.value + idx.kind.value < 0 ||
-                //             end.kind.value + idx.kind.value >= values.length
-                //         ) {
-                //             throw new Error();
-                //         }
-                //         this.regs.set(
-                //             inst,
-                //             values[begin.kind.value + idx.kind.value],
-                //         );
-                //     } else {
-                //         throw new Error();
-                //     }
-                //     break;
-                // }
-                case "Index": {
+                case "GetElemPtr": {
                     const offset = this.regs.get(k.offset)!;
                     if (offset.kind.tag !== "Int") {
                         throw new Error();
@@ -100,7 +62,10 @@ export class FnInterpreter {
                             console.log({ array });
                             throw new Error();
                         }
-                        if (offset.kind.value >= array.kind.values.length) {
+                        if (
+                            offset.kind.value < 0 ||
+                            offset.kind.value >= array.kind.values.length
+                        ) {
                             throw new Error();
                         }
                         this.regs.set(
@@ -112,8 +77,20 @@ export class FnInterpreter {
                                 mutable: base.kind.mutable,
                             }),
                         );
-                    } else if (base.kind.tag === "Slice") {
-                        throw new Error();
+                    } else if (base.kind.tag === "ArraySlice") {
+                        const idx = offset.kind.value + base.kind.begin;
+                        if (idx < 0 || idx >= base.kind.end) {
+                            throw new Error();
+                        }
+                        this.regs.set(
+                            inst,
+                            new Val({
+                                tag: "ArrayElemPtr",
+                                values: base.kind.values,
+                                idx,
+                                mutable: base.kind.mutable,
+                            }),
+                        );
                     } else {
                         throw new Error();
                     }
@@ -136,29 +113,31 @@ export class FnInterpreter {
                     if (value.kind.tag !== "Array") {
                         throw new Error();
                     }
-                    if (
-                        begin && begin.kind.tag === "Int" &&
-                        begin.kind.value < 0
-                    ) {
-                        throw new Error();
+                    let beginIdx = 0;
+                    if (begin) {
+                        if (begin.kind.tag !== "Int") {
+                            throw new Error();
+                        }
+                        beginIdx = begin.kind.value;
                     }
-                    if (
-                        end && end.kind.tag === "Int" &&
-                        end.kind.value >= value.kind.values.length
-                    ) {
+                    let endIdx = value.kind.values.length;
+                    if (end) {
+                        if (end.kind.tag !== "Int") {
+                            throw new Error();
+                        }
+                        endIdx = end.kind.value;
+                    }
+                    if (beginIdx < 0 || endIdx > value.kind.values.length) {
                         throw new Error();
                     }
                     this.regs.set(
                         inst,
                         new Val({
-                            tag: "Slice",
-                            value,
-                            begin: begin ?? new Val({ tag: "Int", value: 0 }),
-                            end: end ??
-                                new Val({
-                                    tag: "Int",
-                                    value: value.kind.values.length,
-                                }),
+                            tag: "ArraySlice",
+                            mutable: false,
+                            values: value.kind.values,
+                            begin: beginIdx,
+                            end: endIdx,
                         }),
                     );
                     break;
@@ -194,6 +173,7 @@ export class FnInterpreter {
                             source.kind.values[source.kind.idx],
                         );
                     } else {
+                        console.log({ source });
                         throw new Error();
                     }
                     break;
@@ -207,6 +187,7 @@ export class FnInterpreter {
                         const source = this.regs.get(k.source)!;
                         target.kind.values[target.kind.idx] = source;
                     } else {
+                        console.log({ target });
                         throw new Error();
                     }
                     break;
@@ -357,18 +338,12 @@ class Val {
             case "Ptr":
             case "ArrayElemPtr":
                 return `<pointer>`;
-            case "Slice":
-                if (k.value.kind.tag !== "Array") {
-                    throw new Error();
-                }
-                if (k.begin.kind.tag !== "Int" || k.end.kind.tag !== "Int") {
-                    throw new Error();
-                }
+            case "ArraySlice":
                 return `[${
-                    k.value.kind.values.slice(
-                        k.begin.kind.value,
-                        k.end.kind.value,
-                    ).map((v) => v.pretty()).join(", ")
+                    k.values
+                        .slice(k.begin, k.end)
+                        .map((v) => v.pretty())
+                        .join(", ")
                 }]`;
             case "Array":
                 return `[${k.values.map((v) => v.pretty()).join(", ")}]`;
@@ -388,6 +363,12 @@ type ValKind =
     | { tag: "Bool"; value: boolean }
     | { tag: "Ptr"; mutable: boolean; value: Val }
     | { tag: "ArrayElemPtr"; mutable: boolean; values: Val[]; idx: number }
-    | { tag: "Slice"; value: Val; begin: Val; end: Val }
+    | {
+        tag: "ArraySlice";
+        mutable: boolean;
+        values: Val[];
+        begin: number;
+        end: number;
+    }
     | { tag: "Array"; values: Val[] }
     | { tag: "Fn"; fn: mir.Fn };
diff --git a/src/ty.ts b/src/ty.ts
index 05ab78e..8f912d5 100644
--- a/src/ty.ts
+++ b/src/ty.ts
@@ -122,6 +122,13 @@ export class Ty {
         throw new Error(`'${this.kind.tag}' not handled`);
     }
 
+    isSized(): boolean {
+        if (this.is("Slice")) {
+            return false;
+        }
+        return true;
+    }
+
     pretty(): string {
         switch (this.kind.tag) {
             case "Error":
diff --git a/tests/array.ethlang b/tests/array.ethlang
index 8261ff4..61bbf9d 100644
--- a/tests/array.ethlang
+++ b/tests/array.ethlang
@@ -12,13 +12,13 @@ fn main()
     print_int(ptr_to_array.*[1]);
 
     let slice: *[int] = &array[..];
-    // // e xpect: 2
-    // print_int(slice.*[2]);
+    // expect: 3
+    print_int(slice.*[2]);
 
-    // let slice_mut: *mut [int] = &mut array[1..3];
-    // slice_mut.*[0] = 4;
-    // // e xpect: 4
-    // print_int(array[1]);
+    let slice_mut: *mut [int] = &mut array[1..3];
+    slice_mut.*[0] = 4;
+    // expect: 4
+    print_int(array[1]);
 }
 
 // vim: syntax=rust commentstring=//\ %s
diff --git a/tests/_pointer.ethlang b/tests/pointer.ethlang
similarity index 97%
rename from tests/_pointer.ethlang
rename to tests/pointer.ethlang
index a693c72..7c19ba7 100644
--- a/tests/_pointer.ethlang
+++ b/tests/pointer.ethlang
@@ -8,25 +8,21 @@ fn main()
 {
     let a = 1;
     let b: *int = &a;
-    
     // expect: 1
     print_int(*b);
 
     a = 2;
-
     // expect: 2
     print_int(*b);
 
     let c: *mut int = &mut a;
     *c = 3;
-
     // expect: 3
     print_int(a);
     // expect: 3
     print_int(*c);
 
     change_to(&mut a, 4);
-
     // expect: 4
     print_int(a);
 }