From f4886e045c82f49b05e1cac9f547afe79dc2095e Mon Sep 17 00:00:00 2001
From: SimonFJ20 <simonfromjakobsen@gmail.com>
Date: Thu, 6 Feb 2025 14:52:45 +0100
Subject: [PATCH] compiler: finish example ast lower

---
 slige/compiler/check/checker.ts      |  82 ++++++++++--
 slige/compiler/common/diagnostics.ts | 128 ++++++++++---------
 slige/compiler/deno.jsonc            |  15 ++-
 slige/compiler/main.ts               |  13 +-
 slige/compiler/middle/ast_lower.ts   | 120 +++++++++++++++++-
 slige/compiler/middle/mir.ts         |   7 +-
 slige/compiler/middle/mod.ts         |   2 +
 slige/compiler/parse/lexer.ts        |   2 +-
 slige/compiler/resolve/cx.ts         |   2 +-
 slige/compiler/resolve/resolver.ts   |   9 +-
 slige/compiler/stringify/deno.jsonc  |   4 +
 slige/compiler/stringify/hir.ts      | 178 +++++++++++++++++++++++++++
 slige/compiler/stringify/mir.ts      | 168 +++++++++++++++++++++++++
 slige/compiler/stringify/mod.ts      |   2 +
 14 files changed, 644 insertions(+), 88 deletions(-)
 create mode 100644 slige/compiler/middle/mod.ts
 create mode 100644 slige/compiler/stringify/deno.jsonc
 create mode 100644 slige/compiler/stringify/hir.ts
 create mode 100644 slige/compiler/stringify/mir.ts
 create mode 100644 slige/compiler/stringify/mod.ts

diff --git a/slige/compiler/check/checker.ts b/slige/compiler/check/checker.ts
index 3aaf75b..a46ba3e 100644
--- a/slige/compiler/check/checker.ts
+++ b/slige/compiler/check/checker.ts
@@ -48,7 +48,13 @@ export class Checker {
 
         const exprTy = kind.expr && Ok(this.exprTy(kind.expr));
         const tyTy = kind.ty && Ok(this.tyTy(kind.ty));
-        const ty = exprTy && tyTy && this.resolveTys(exprTy.val, tyTy.val);
+        const ty = exprTy !== undefined
+            ? tyTy !== undefined
+                ? this.resolveTys(exprTy.val, tyTy.val)
+                : exprTy
+            : exprTy;
+
+        this.stmtChecked.add(stmt.id);
 
         if (ty === undefined) {
             this.report("type amfibious, specify type or value", stmt.span);
@@ -65,8 +71,6 @@ export class Checker {
             this.report(res.val, stmt.span);
             return Ty({ tag: "error" });
         }
-
-        this.stmtChecked.add(stmt.id);
     }
 
     private assignPatTy(pat: ast.Pat, ty: Ty): Res<void, string> {
@@ -108,9 +112,9 @@ export class Checker {
             case "path":
                 return this.checkPathExpr(expr, k, expected);
             case "null":
-                return todo();
+                return Ty({ tag: "null" });
             case "int":
-                return todo();
+                return Ty({ tag: "int" });
             case "bool":
                 return todo();
             case "str":
@@ -134,7 +138,7 @@ export class Checker {
             case "index":
                 return todo();
             case "call":
-                return todo();
+                return this.checkCallExpr(expr, k, expected);
             case "unary":
                 return todo();
             case "binary":
@@ -188,6 +192,35 @@ export class Checker {
         exhausted(res.kind);
     }
 
+    private checkCallExpr(
+        expr: ast.Expr,
+        kind: ast.CallExpr,
+        expected: Ty,
+    ): Ty {
+        const fnTy = this.exprTy(kind.expr);
+        if (fnTy.kind.tag !== "fn") {
+            if (fnTy.kind.tag === "error") {
+                return fnTy;
+            }
+            const ty = tyToString(this.ctx, fnTy);
+            console.log(kind.expr.span);
+            this.report(`type '${ty}' not fucking callable`, kind.expr.span);
+            return Ty({ tag: "error" });
+        }
+        const paramTys = fnTy.kind.params;
+        if (paramTys.length !== kind.args.length) {
+            this.report(
+                "not enough/too many fucking arguments",
+                kind.expr.span,
+            );
+            return Ty({ tag: "error" });
+        }
+        const _args = kind.args.map((arg, i) =>
+            this.checkExpr(arg, paramTys[i])
+        );
+        return fnTy.kind.returnTy;
+    }
+
     private tyTy(ty: ast.Ty): Ty {
         return this.tyTys.get(ty.id) ||
             this.checkTy(ty);
@@ -227,10 +260,29 @@ export class Checker {
                 return todo();
             case "bind": {
                 switch (patRes.kind.tag) {
-                    case "fn_param":
-                        return todo();
-                    case "let":
-                        return todo();
+                    case "fn_param": {
+                        const fnTy = this.fnItemTy(
+                            patRes.kind.item,
+                            patRes.kind.kind,
+                        );
+                        if (fnTy.kind.tag !== "fn") {
+                            throw new Error();
+                        }
+                        const paramTy = fnTy.kind.params[patRes.kind.paramIdx];
+                        this.assignPatTy(
+                            patRes.kind.kind.params[patRes.kind.paramIdx].pat,
+                            paramTy,
+                        );
+                        const ty = this.patTy(pat);
+                        this.patTys.set(pat.id, ty);
+                        return ty;
+                    }
+                    case "let": {
+                        this.checkLetStmtTy(patRes.kind.stmt, patRes.kind.kind);
+                        const ty = this.patTy(pat);
+                        this.patTys.set(pat.id, ty);
+                        return ty;
+                    }
                 }
                 exhausted(patRes.kind);
                 return todo();
@@ -242,6 +294,12 @@ export class Checker {
     }
 
     private resolveTys(a: Ty, b: Ty): Res<Ty, string> {
+        if (a.kind.tag === "error" || b.kind.tag === "error") {
+            return Res.Ok(a);
+        }
+        if (b.kind.tag === "unknown") {
+            return Res.Ok(a);
+        }
         const as = tyToString(this.ctx, a);
         const bs = tyToString(this.ctx, b);
         const incompat = () =>
@@ -249,10 +307,8 @@ export class Checker {
                 `type '${as}' not compatible with type '${bs}'`,
             );
         switch (a.kind.tag) {
-            case "error":
-                return Res.Ok(b);
             case "unknown":
-                return Res.Ok(b);
+                return this.resolveTys(b, a);
             case "null": {
                 if (b.kind.tag !== "null") {
                     return incompat();
diff --git a/slige/compiler/common/diagnostics.ts b/slige/compiler/common/diagnostics.ts
index 35d7e6a..7f5d06a 100644
--- a/slige/compiler/common/diagnostics.ts
+++ b/slige/compiler/common/diagnostics.ts
@@ -25,6 +25,10 @@ export type Report = {
     pos?: Pos;
 };
 
+export type ReportLocation =
+    | { file: File; span: Span }
+    | { file: File; pos: Pos };
+
 function severityColor(severity: "fatal" | "error" | "warning" | "info") {
     switch (severity) {
         case "fatal":
@@ -40,6 +44,13 @@ function severityColor(severity: "fatal" | "error" | "warning" | "info") {
 }
 
 export function prettyPrintReport(ctx: Ctx, rep: Report) {
+    if (rep.span && rep.span.begin.idx === rep.span.end.idx) {
+        return prettyPrintReport(ctx, {
+            ...rep,
+            span: undefined,
+            pos: rep.span.begin,
+        });
+    }
     const { severity, msg } = rep;
     const origin = rep.origin ? `\x1b[1m${rep.origin}:\x1b[0m ` : "";
     console.error(
@@ -47,71 +58,72 @@ export function prettyPrintReport(ctx: Ctx, rep: Report) {
             severityColor(severity)
         }${severity}:\x1b[0m \x1b[37m${msg}\x1b[0m`,
     );
-    if (rep.file && (rep.span || rep.pos)) {
-        const errorLineOffset = 2;
-        const { absPath: path } = ctx.fileInfo(rep.file);
-        const { line, col } = rep.span?.begin ?? rep.pos!;
-        console.error(`    --> ./${path}:${line}:${col}`);
-        if (rep.span) {
-            const spanLines = ctx.fileSpanText(rep.file, rep.span).split("\n");
-            spanLines.pop();
-            if (spanLines.length == 1) {
-                console.error(
-                    `${rep.span.begin.line.toString().padStart(4, " ")}| ${
-                        spanLines[0]
-                    }`,
-                );
-                console.error(
-                    `    | ${severityColor(severity)}${
-                        " ".repeat(rep.span.begin.col)
-                    }${
-                        "~".repeat(rep.span.end.col - rep.span.begin.col)
-                    }\x1b[0m`,
-                );
-                return;
-            }
-            for (let i = 0; i < spanLines.length; i++) {
-                console.error(
-                    `${
-                        (rep.span.begin.line + i).toString().padStart(4, " ")
-                    }| ${spanLines[i]}`,
-                );
-                if (i == 0) {
-                    console.error(
-                        `    | ${" ".repeat(rep.span.begin.col - 1)}${
-                            severityColor(severity)
-                        }${
-                            "~".repeat(
-                                spanLines[i].length - (rep.span.begin.col - 1),
-                            )
-                        }\x1b[0m`,
-                    );
-                } else if (i == spanLines.length - 1) {
-                    console.error(
-                        `    | ${severityColor(severity)}${
-                            "~".repeat(rep.span.end.col)
-                        }\x1b[0m`,
-                    );
-                } else {
-                    console.error(
-                        `    | ${severityColor(severity)}${
-                            "~".repeat(spanLines[i].length)
-                        }\x1b[0m`,
-                    );
-                }
-            }
-        } else if (rep.pos) {
+    if (!rep.file) {
+        return;
+    }
+    const errorLineOffset = 2;
+    const { absPath: path } = ctx.fileInfo(rep.file);
+    const { line, col } = rep.span?.begin ?? rep.pos!;
+    console.error(`    --> ./${path}:${line}:${col}`);
+    if (rep.span) {
+        const spanLines = ctx.fileSpanText(rep.file, rep.span).split("\n");
+        spanLines.pop();
+        if (spanLines.length == 1) {
             console.error(
-                `${rep.pos.line.toString().padStart(4, " ")}| ${
-                    ctx.filePosLineText(rep.file, rep.pos)
+                `${rep.span.begin.line.toString().padStart(4, " ")}| ${
+                    spanLines[0]
                 }`,
             );
             console.error(
                 `    | ${severityColor(severity)}${
-                    " ".repeat(rep.pos.col)
-                }^\x1b[0m`,
+                    " ".repeat(rep.span.begin.col - 1)
+                }${
+                    "~".repeat(rep.span.end.col - rep.span.begin.col + 1)
+                }\x1b[0m`,
             );
+            return;
         }
+        for (let i = 0; i < spanLines.length; i++) {
+            console.error(
+                `${(rep.span.begin.line + i).toString().padStart(4, " ")}| ${
+                    spanLines[i]
+                }`,
+            );
+            if (i == 0) {
+                console.error(
+                    `    | ${" ".repeat(rep.span.begin.col - 1)}${
+                        severityColor(severity)
+                    }${
+                        "~".repeat(
+                            spanLines[i].length - (rep.span.begin.col - 1),
+                        )
+                    }\x1b[0m`,
+                );
+            } else if (i == spanLines.length - 1) {
+                console.error(
+                    `    | ${severityColor(severity)}${
+                        "~".repeat(rep.span.end.col)
+                    }\x1b[0m`,
+                );
+            } else {
+                console.error(
+                    `    | ${severityColor(severity)}${
+                        "~".repeat(spanLines[i].length)
+                    }\x1b[0m`,
+                );
+            }
+        }
+    } else if (rep.pos) {
+        console.error(
+            `${rep.pos.line.toString().padStart(4, " ")}| ${
+                ctx.filePosLineText(rep.file, rep.pos)
+            }`,
+        );
+        console.error(
+            `    | ${severityColor(severity)}${
+                " ".repeat(rep.pos.col - 1)
+            }^\x1b[0m`,
+        );
     }
 }
 
diff --git a/slige/compiler/deno.jsonc b/slige/compiler/deno.jsonc
index b8ccffe..5f22490 100644
--- a/slige/compiler/deno.jsonc
+++ b/slige/compiler/deno.jsonc
@@ -1,15 +1,24 @@
 {
-    "workspace": ["./ast", "./check", "./middle", "./parse", "./resolve", "./ty", "./common"],
+    "workspace": [
+        "./ast",
+        "./check",
+        "./middle",
+        "./parse",
+        "./resolve",
+        "./ty",
+        "./common",
+        "./stringify"
+    ],
     "lint": {
         "rules": {
             "tags": ["recommended"],
             "exclude": [
                 "verbatim-module-syntax",
                 "no-unused-vars"
-            ],
+            ]
         }
     },
     "fmt": {
         "indentWidth": 4
-    },
+    }
 }
diff --git a/slige/compiler/main.ts b/slige/compiler/main.ts
index f03c2b7..7bc3c46 100644
--- a/slige/compiler/main.ts
+++ b/slige/compiler/main.ts
@@ -5,6 +5,7 @@ import { Ctx, File } from "@slige/common";
 import { Resolver } from "./resolve/resolver.ts";
 import { Checker } from "./check/checker.ts";
 import { AstLowerer } from "./middle/ast_lower.ts";
+import { HirStringifyer } from "@slige/stringify";
 
 async function main() {
     const filePath = Deno.args[0];
@@ -43,7 +44,17 @@ export class PackCompiler {
             .collect();
         const resols = new Resolver(this.ctx, entryFileAst).resolve();
         const checker = new Checker(this.ctx, entryFileAst, resols);
-        new AstLowerer(this.ctx, resols, checker, entryFileAst).lower();
+        console.log(
+            "=== HIR ===\n" + new HirStringifyer(checker).file(entryFileAst),
+        );
+        const astLowerer = new AstLowerer(
+            this.ctx,
+            resols,
+            checker,
+            entryFileAst,
+        );
+        astLowerer.lower();
+        console.log("=== MIR ===\n" + astLowerer.mirString());
     }
 
     public enableDebug() {
diff --git a/slige/compiler/middle/ast_lower.ts b/slige/compiler/middle/ast_lower.ts
index 2c970e1..6a6c44f 100644
--- a/slige/compiler/middle/ast_lower.ts
+++ b/slige/compiler/middle/ast_lower.ts
@@ -3,10 +3,20 @@ import { Checker } from "@slige/check";
 import { AstId, Ctx, exhausted, IdMap, Ids, Res, todo } from "@slige/common";
 import { Resols } from "@slige/resolve";
 import { Ty } from "@slige/ty";
-import { BinaryType, Operand, StmtKind, TerKind } from "./mir.ts";
+import {
+    BinaryType,
+    Operand,
+    Place,
+    ProjElem,
+    StmtKind,
+    TerKind,
+} from "./mir.ts";
 import { Block, BlockId, Fn, Local, LocalId, RVal, Stmt, Ter } from "./mir.ts";
+import { MirFnStringifyer } from "@slige/stringify";
 
 export class AstLowerer implements ast.Visitor {
+    private fns = new IdMap<AstId, Fn>();
+
     public constructor(
         private ctx: Ctx,
         private re: Resols,
@@ -19,7 +29,18 @@ export class AstLowerer implements ast.Visitor {
     }
 
     visitFnItem(item: ast.Item, kind: ast.FnItem): ast.VisitRes {
-        new FnLowerer(this.ctx, this.re, this.ch, item, kind).lower();
+        const fn = new FnLowerer(this.ctx, this.re, this.ch, item, kind)
+            .lower();
+        if (fn.ok) {
+            this.fns.set(item.id, fn.val);
+        }
+    }
+
+    public mirString(): string {
+        return this.fns.values()
+            .map((fn) => new MirFnStringifyer(this.ctx).fn(fn))
+            .toArray()
+            .join("\n");
     }
 }
 
@@ -46,7 +67,10 @@ export class FnLowerer {
         const entry = this.pushBlock();
 
         const fnTy = this.ch.fnItemTy(this.item, this.kind);
-        const returnPlace = this.local(fnTy);
+        if (fnTy.kind.tag !== "fn") {
+            throw new Error();
+        }
+        const returnPlace = this.local(fnTy.kind.returnTy);
         const returnVal = this.lowerBlock(this.kind.body!);
 
         this.addStmt({
@@ -81,12 +105,68 @@ export class FnLowerer {
             case "error":
                 return { tag: "error" };
             case "item":
+                return todo(k.tag);
             case "let":
+                return this.lowerLetStmt(stmt, k);
             case "return":
             case "break":
             case "continue":
             case "assign":
             case "expr":
+                return todo(k.tag);
+        }
+        exhausted(k);
+    }
+
+    private lowerLetStmt(_stmt: ast.Stmt, kind: ast.LetStmt) {
+        const val = kind.expr && this.lowerExpr(kind.expr);
+        this.allocatePat(kind.pat);
+        if (val) {
+            const local = this.local(this.ch.patTy(kind.pat));
+            this.addStmt({
+                tag: "assign",
+                place: { local: local, proj: [] },
+                rval: val,
+            });
+            this.assignPat(kind.pat, local, []);
+        }
+    }
+
+    private allocatePat(pat: ast.Pat) {
+        const k = pat.kind;
+        switch (k.tag) {
+            case "error":
+                return;
+            case "bind": {
+                const ty = this.ch.patTy(pat);
+                const local = this.local(ty);
+                this.reLocals.set(pat.id, local);
+                return;
+            }
+            case "path":
+                return todo();
+        }
+        exhausted(k);
+    }
+
+    private assignPat(pat: ast.Pat, local: LocalId, proj: ProjElem[]) {
+        const k = pat.kind;
+        switch (k.tag) {
+            case "error":
+                return;
+            case "bind": {
+                const patLocal = this.reLocals.get(pat.id)!;
+                this.addStmt({
+                    tag: "assign",
+                    place: { local: patLocal, proj: [] },
+                    rval: {
+                        tag: "use",
+                        operand: { tag: "move", place: { local, proj } },
+                    },
+                });
+                return;
+            }
+            case "path":
                 return todo();
         }
         exhausted(k);
@@ -100,7 +180,18 @@ export class FnLowerer {
             case "path":
                 return this.lowerPathExpr(expr, k);
             case "null":
+                return {
+                    tag: "use",
+                    operand: { tag: "const", val: { tag: "null" } },
+                };
             case "int":
+                return {
+                    tag: "use",
+                    operand: {
+                        tag: "const",
+                        val: { tag: "int", value: k.value },
+                    },
+                };
             case "bool":
             case "str":
             case "group":
@@ -112,7 +203,9 @@ export class FnLowerer {
             case "elem":
             case "field":
             case "index":
+                return todo(k.tag);
             case "call":
+                return this.lowerCallExpr(expr, k);
             case "unary":
                 return todo(k.tag);
             case "binary":
@@ -133,8 +226,14 @@ export class FnLowerer {
         switch (re.kind.tag) {
             case "error":
                 return { tag: "error" };
-            case "fn":
-                return todo();
+            case "fn": {
+                const ty = this.ch.fnItemTy(re.kind.item, re.kind.kind);
+                const local = this.local(ty);
+                return {
+                    tag: "use",
+                    operand: { tag: "move", place: { local, proj: [] } },
+                };
+            }
             case "local": {
                 const ty = this.ch.exprTy(expr);
                 const local = this.local(ty);
@@ -164,6 +263,17 @@ export class FnLowerer {
         exhausted(re.kind);
     }
 
+    private lowerCallExpr(expr: ast.Expr, kind: ast.CallExpr): RVal {
+        const args = kind.args.map((arg) =>
+            this.rvalAsOperand(this.lowerExpr(arg), this.ch.exprTy(arg))
+        );
+        const func = this.rvalAsOperand(
+            this.lowerExpr(kind.expr),
+            this.ch.exprTy(expr),
+        );
+        return { tag: "call", func, args };
+    }
+
     private lowerBinaryExpr(expr: ast.Expr, kind: ast.BinaryExpr): RVal {
         const left = this.rvalAsOperand(
             this.lowerExpr(kind.left),
diff --git a/slige/compiler/middle/mir.ts b/slige/compiler/middle/mir.ts
index b42175a..f655904 100644
--- a/slige/compiler/middle/mir.ts
+++ b/slige/compiler/middle/mir.ts
@@ -51,8 +51,7 @@ export type TerKind =
     }
     | { tag: "return" }
     | { tag: "unreachable" }
-    | { tag: "drop"; place: Place; target: BlockId }
-    | { tag: "call"; func: Operand; args: Operand[]; dest: Operand };
+    | { tag: "drop"; place: Place; target: BlockId };
 
 export type SwitchTarget = {
     value: number;
@@ -67,7 +66,6 @@ export type Place = {
 // https://doc.rust-lang.org/beta/nightly-rustc/rustc_middle/mir/type.PlaceElem.html
 export type ProjElem =
     | { tag: "deref" }
-    | { tag: "repeat" }
     | { tag: "field"; fieldIdx: number }
     | { tag: "index"; local: LocalId }
     | { tag: "downcast"; variantIdx: number };
@@ -80,7 +78,8 @@ export type RVal =
     | { tag: "ref"; place: Place; mut: boolean }
     | { tag: "ptr"; place: Place; mut: boolean }
     | { tag: "binary"; binaryType: BinaryType; left: Operand; right: Operand }
-    | { tag: "unary"; unaryType: UnaryType; operand: Operand };
+    | { tag: "unary"; unaryType: UnaryType; operand: Operand }
+    | { tag: "call"; func: Operand; args: Operand[] };
 
 export type BinaryType =
     | "add"
diff --git a/slige/compiler/middle/mod.ts b/slige/compiler/middle/mod.ts
new file mode 100644
index 0000000..353fac5
--- /dev/null
+++ b/slige/compiler/middle/mod.ts
@@ -0,0 +1,2 @@
+export * from "./mir.ts";
+export * from "./ast_lower.ts";
diff --git a/slige/compiler/parse/lexer.ts b/slige/compiler/parse/lexer.ts
index 510f4a8..d8bbe55 100644
--- a/slige/compiler/parse/lexer.ts
+++ b/slige/compiler/parse/lexer.ts
@@ -203,7 +203,7 @@ export class Lexer implements TokenIter {
         let val = this.current();
         this.step();
         while (this.test(tailPat)) {
-            end = begin;
+            end = this.pos();
             val += this.current();
             this.step();
         }
diff --git a/slige/compiler/resolve/cx.ts b/slige/compiler/resolve/cx.ts
index e782633..3362d97 100644
--- a/slige/compiler/resolve/cx.ts
+++ b/slige/compiler/resolve/cx.ts
@@ -25,7 +25,7 @@ export type PatResolve = {
 };
 
 export type PatResolveKind =
-    | { tag: "fn_param"; paramIdx: number }
+    | { tag: "fn_param"; item: ast.Item; kind: ast.FnItem; paramIdx: number }
     | { tag: "let"; stmt: ast.Stmt; kind: ast.LetStmt };
 
 export const ResolveError = (ident: ast.Ident): Resolve => ({
diff --git a/slige/compiler/resolve/resolver.ts b/slige/compiler/resolve/resolver.ts
index ecc0e71..72626ca 100644
--- a/slige/compiler/resolve/resolver.ts
+++ b/slige/compiler/resolve/resolver.ts
@@ -118,12 +118,17 @@ export class Resolver implements ast.Visitor {
     }
 
     private popAndVisitFnBodies() {
-        for (const [_item, kind] of this.fnBodiesToCheck.at(-1)!) {
+        for (const [item, kind] of this.fnBodiesToCheck.at(-1)!) {
             const outerSyms = this.syms;
             this.syms = new FnSyms(this.syms);
             this.syms = new LocalSyms(this.syms);
             for (const [paramIdx, param] of kind.params.entries()) {
-                this.patResolveStack.push({ tag: "fn_param", paramIdx });
+                this.patResolveStack.push({
+                    tag: "fn_param",
+                    item,
+                    kind,
+                    paramIdx,
+                });
                 ast.visitParam(this, param);
                 this.patResolveStack.pop();
             }
diff --git a/slige/compiler/stringify/deno.jsonc b/slige/compiler/stringify/deno.jsonc
new file mode 100644
index 0000000..8d0cb0b
--- /dev/null
+++ b/slige/compiler/stringify/deno.jsonc
@@ -0,0 +1,4 @@
+{
+    "name": "@slige/stringify",
+    "exports": "./mod.ts",
+}
diff --git a/slige/compiler/stringify/hir.ts b/slige/compiler/stringify/hir.ts
new file mode 100644
index 0000000..6e11a30
--- /dev/null
+++ b/slige/compiler/stringify/hir.ts
@@ -0,0 +1,178 @@
+import * as ast from "@slige/ast";
+import { exhausted, todo } from "@slige/common";
+import { Checker } from "@slige/check";
+import { Ty } from "@slige/ty";
+
+export class HirStringifyer {
+    public constructor(
+        private ch: Checker,
+    ) {}
+
+    public file(file: ast.File, depth = 0): string {
+        return file.stmts.map((stmt) =>
+            indent(depth) + this.stmt(stmt, depth + 1)
+        ).join("\n");
+    }
+
+    public stmt(stmt: ast.Stmt, depth = 0): string {
+        const k = stmt.kind;
+        switch (k.tag) {
+            case "error":
+                return "<error>;";
+            case "item":
+                return this.item(k.item);
+            case "let":
+                return `let ${this.pat(k.pat)}${
+                    k.expr && ` = ${this.expr(k.expr)}` || ""
+                };`;
+            case "return":
+                return `return${k.expr && ` ${this.expr(k.expr)}` || ""};`;
+            case "break":
+                return `break${k.expr && ` ${this.expr(k.expr)}` || ""};`;
+            case "continue":
+                return `continue;`;
+            case "assign":
+                return `${this.expr(k.subject)} = ${this.expr(k.value)};`;
+            case "expr":
+                return `${this.expr(k.expr)};`;
+        }
+        exhausted(k);
+    }
+
+    public item(item: ast.Item, depth = 0): string {
+        const ident = item.ident.text;
+        const pub = item.pub ? "pub " : "";
+        const k = item.kind;
+        switch (k.tag) {
+            case "error":
+                return "<error>;";
+            case "mod_block":
+                return `${pub}mod ${ident} ${this.block(k.block, depth)}`;
+            case "mod_file":
+                return `${pub}mod ${ident} {\n${
+                    this.file(k.ast!, depth + 1)
+                }\n}`;
+            case "enum":
+                return todo();
+            case "struct":
+                return todo();
+            case "fn": {
+                const ty = this.ch.fnItemTy(item, k);
+                if (ty.kind.tag !== "fn") {
+                    throw new Error();
+                }
+                const params = k.params
+                    .map((param) => this.pat(param.pat))
+                    .join(", ");
+                return `${pub}fn ${ident}(${params}) -> ${
+                    this.ty(ty.kind.returnTy)
+                } ${this.block(k.body!, depth)}`;
+            }
+            case "use":
+                return todo();
+            case "type_alias":
+                return todo();
+        }
+        exhausted(k);
+    }
+
+    public expr(expr: ast.Expr, depth = 0): string {
+        const k = expr.kind;
+        switch (k.tag) {
+            case "error":
+                return "<error>";
+            case "path":
+                return this.path(k.path);
+            case "null":
+                return "null";
+            case "int":
+                return `${k.value}`;
+            case "bool":
+                return `${k.value}`;
+            case "str":
+                return `"${k.value}"`;
+            case "group":
+            case "array":
+            case "repeat":
+            case "struct":
+            case "ref":
+            case "deref":
+            case "elem":
+            case "field":
+            case "index":
+                return todo(k.tag);
+            case "call":
+                return `${this.expr(k.expr)}(${
+                    k.args.map((arg) => this.expr(arg)).join(", ")
+                })`;
+            case "unary":
+                return todo(k.tag);
+            case "binary":
+                return `${this.expr(k.left)} ${k.binaryType} ${
+                    this.expr(k.right)
+                }`;
+            case "block":
+            case "if":
+            case "loop":
+            case "while":
+            case "for":
+            case "c_for":
+                return todo(k.tag);
+        }
+        exhausted(k);
+    }
+
+    public pat(pat: ast.Pat, depth = 0): string {
+        const k = pat.kind;
+        switch (k.tag) {
+            case "error":
+                return "<error>";
+            case "bind":
+                return `${k.mut ? "mut " : ""}${k.ident.text}: ${
+                    this.ty(this.ch.patTy(pat))
+                }`;
+            case "path":
+                return todo();
+        }
+        exhausted(k);
+    }
+
+    public block(block: ast.Block, depth = 0): string {
+        return `{\n${
+            [
+                ...block.stmts
+                    .map((stmt) => this.stmt(stmt, depth + 1)),
+                ...(block.expr ? [this.expr(block.expr)] : []),
+            ]
+                .map((str) => indent(depth + 1) + str)
+                .join("\n")
+        }\n${indent(depth)}}`;
+    }
+
+    public path(path: ast.Path): string {
+        return path.segments.map((seg) => seg.ident.text).join("::");
+    }
+
+    public ty(ty: Ty): string {
+        const k = ty.kind;
+        switch (k.tag) {
+            case "error":
+                return "<error>";
+            case "unknown":
+                return "<unknown>";
+            case "null":
+                return "null";
+            case "int":
+                return "int";
+            case "fn":
+                return `fn ${k.item.ident}(${
+                    k.params.map((param) => this.ty(param)).join(", ")
+                }) -> ${this.ty(k.returnTy)}`;
+        }
+        exhausted(k);
+    }
+}
+
+function indent(depth: number): string {
+    return "    ".repeat(depth);
+}
diff --git a/slige/compiler/stringify/mir.ts b/slige/compiler/stringify/mir.ts
new file mode 100644
index 0000000..1490de6
--- /dev/null
+++ b/slige/compiler/stringify/mir.ts
@@ -0,0 +1,168 @@
+import {
+    Block,
+    BlockId,
+    Const,
+    Fn,
+    Local,
+    LocalId,
+    Operand,
+    Place,
+    ProjElem,
+    RVal,
+    Stmt,
+    StmtKind,
+    Ter,
+} from "@slige/middle";
+import { Ctx, exhausted, IdMap, todo } from "@slige/common";
+import { Checker } from "@slige/check";
+import { Ty, tyToString } from "@slige/ty";
+
+export class MirFnStringifyer {
+    private blockIds = new IdMap<BlockId, number>();
+    private localIds = new IdMap<LocalId, number>();
+
+    public constructor(
+        private ctx: Ctx,
+    ) {}
+
+    public fn(fn: Fn): string {
+        return `fn ${fn.label} {\n${
+            fn.locals.values().toArray()
+                .map((local) => this.localDef(local))
+                .join("\n")
+        }\n${
+            fn.blocks.values().toArray()
+                .map((block) => this.block(block))
+                .join("\n")
+        }\n}`.replaceAll("#", "    ");
+    }
+
+    private localDef(local: Local): string {
+        const id = this.localIds.size;
+        this.localIds.set(local.id, id);
+        return `#let %${id}: ${tyToString(this.ctx, local.ty)}`;
+    }
+
+    private block(block: Block): string {
+        const id = this.blockIds.size;
+        this.blockIds.set(block.id, id);
+        return `#.b${id}: {\n${
+            block.stmts
+                .map((stmt) => this.stmt(stmt))
+                .join("\n")
+        }\n${this.ter(block.terminator)}\n#}`;
+    }
+
+    private stmt(stmt: Stmt): string {
+        const k = stmt.kind;
+        switch (k.tag) {
+            case "error":
+                return "##<error>;";
+            case "assign":
+                return `##${this.place(k.place)} = ${this.rval(k.rval)}`;
+            case "fake_read":
+            case "deinit":
+            case "live":
+            case "dead":
+            case "mention":
+                return todo();
+        }
+        exhausted(k);
+    }
+
+    private ter(ter: Ter): string {
+        const k = ter.kind;
+        switch (k.tag) {
+            case "unset":
+                return "##<unset>;";
+            case "goto":
+            case "switch":
+                return todo(k.tag);
+            case "return":
+                return `##return;`;
+            case "unreachable":
+            case "drop":
+                return todo(k.tag);
+        }
+        exhausted(k);
+    }
+
+    private place(place: Place): string {
+        return this.placeWithProj(place.local, place.proj);
+    }
+
+    private placeWithProj(local: LocalId, elems: ProjElem[]): string {
+        if (elems.length === 0) {
+            return this.local(local);
+        }
+        const elem = elems[0];
+        const tail = elems.slice(1);
+        switch (elem.tag) {
+            case "deref":
+                return `*${this.placeWithProj(local, tail)}`;
+            case "field":
+                return `${this.placeWithProj(local, tail)}.${elem.fieldIdx}`;
+            case "index":
+                return `${this.placeWithProj(local, tail)}[${
+                    this.local(elem.local)
+                }]`;
+            case "downcast":
+                return todo();
+        }
+        exhausted(elem);
+    }
+
+    private rval(rval: RVal): string {
+        switch (rval.tag) {
+            case "error":
+                return "<error>";
+            case "use":
+                return `${this.operand(rval.operand)}`;
+            case "repeat":
+            case "ref":
+            case "ptr":
+                return todo(rval.tag);
+            case "binary":
+                return `${this.operand(rval.left)} ${rval.binaryType} ${
+                    this.operand(rval.right)
+                }`;
+            case "unary":
+                return todo(rval.tag);
+            case "call":
+                return `${this.operand(rval.func)}(${
+                    rval.args.map((arg) => this.operand(arg)).join(", ")
+                })`;
+        }
+        exhausted(rval);
+    }
+
+    private operand(operand: Operand): string {
+        switch (operand.tag) {
+            case "copy":
+                return `copy ${this.place(operand.place)}`;
+            case "move":
+                return `move ${this.place(operand.place)}`;
+            case "const":
+                return `${this.constVal(operand.val)}`;
+        }
+        exhausted(operand);
+    }
+
+    private constVal(val: Const): string {
+        switch (val.tag) {
+            case "null":
+                return `null`;
+            case "int":
+                return `${val.value}`;
+            case "bool":
+                return `${val.value}`;
+            case "string":
+                return `"${val.value}"`;
+        }
+        exhausted(val);
+    }
+
+    private local(local: LocalId): string {
+        return `%${this.localIds.get(local)!}`;
+    }
+}
diff --git a/slige/compiler/stringify/mod.ts b/slige/compiler/stringify/mod.ts
new file mode 100644
index 0000000..28b54e5
--- /dev/null
+++ b/slige/compiler/stringify/mod.ts
@@ -0,0 +1,2 @@
+export * from "./hir.ts";
+export * from "./mir.ts";