.envrc

@@ -1 +0,0 @@
-use flake

.gitignore

@@ -1,2 +1,3 @@
 /target
-.direnv
+/a.out
+/*.o

Cargo.toml

@@ -1,18 +1,21 @@
 [package]
 name = "gust"
 version = "0.1.0"
-edition = "2021"
-
-[[bin]]
-name = "gustc"
-path = "src/main.rs"
+authors = ["Michael Zhang <mail@mzhang.io>"]
+edition = "2018"
 
 [dependencies]
-anyhow = "1.0.71"
-chalk-engine = "0.91.0"
-clap = { version = "4.3.9", features = ["derive"] }
-lalrpop-util = { version = "0.20.0", features = ["lexer", "regex", "unicode"] }
-redb = "1.0.1"
+anyhow = "1.0.38"
+cranelift = "0.69.0"
+cranelift-module = "0.69.0"
+cranelift-object = "0.69.0"
+lalrpop-util = "0.19.4"
+lazy_static = "1.4.0"
+parking_lot = "0.11.1"
+petgraph = "0.5.1"
+regex = "1.4.3"
+structopt = "0.3.21"
+target-lexicon = "0.11.1"
 
 [build-dependencies]
-lalrpop = "0.20.0"
+lalrpop = "0.19.4"

default.nix

@@ -1,12 +0,0 @@
-{ toolchain, makeRustPlatform, pkg-config }:
-
-let rustPlatform = makeRustPlatform { inherit (toolchain) cargo rustc; };
-
-in rustPlatform.buildRustPackage {
-  name = "liveterm";
-  src = ./.;
-  cargoLock.lockFile = ./Cargo.lock;
-
-  nativeBuildInputs = [ pkg-config ];
-  buildInputs = [ ];
-}

example

@@ -0,0 +1,10 @@
+fn main() {
+    let x = ();
+    urmom();
+    isEven();
+}
+
+fn urmom(x: ()) { return (); }
+
+fn isEven() { return isOdd(); }
+fn isOdd() { return isEven(); }

examples/main.gs

@@ -1,5 +0,0 @@
-from "std" import { fs::{self} };
-
-fn main {
-    5
-}

flake.lock

@@ -1,111 +0,0 @@
-{
-  "nodes": {
-    "fenix": {
-      "inputs": {
-        "nixpkgs": "nixpkgs",
-        "rust-analyzer-src": "rust-analyzer-src"
-      },
-      "locked": {
-        "lastModified": 1687501538,
-        "narHash": "sha256-6uxZWuSoM6rWDPo+7HLCBcNe8+4phnya4qJHS4IlbKo=",
-        "owner": "nix-community",
-        "repo": "fenix",
-        "rev": "3650022df24f0e5545502439ba7599b786455e2a",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "repo": "fenix",
-        "type": "github"
-      }
-    },
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1687171271,
-        "narHash": "sha256-BJlq+ozK2B1sJDQXS3tzJM5a+oVZmi1q0FlBK/Xqv7M=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "abfb11bd1aec8ced1c9bb9adfe68018230f4fb3c",
-        "type": "github"
-      },
-      "original": {
-        "id": "flake-utils",
-        "type": "indirect"
-      }
-    },
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1687412861,
-        "narHash": "sha256-Z/g0wbL68C+mSGerYS2quv9FXQ1RRP082cAC0Bh4vcs=",
-        "owner": "nixos",
-        "repo": "nixpkgs",
-        "rev": "e603dc5f061ca1d8a19b3ede6a8cf9c9fcba6cdc",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nixos",
-        "ref": "nixos-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "nixpkgs_2": {
-      "locked": {
-        "lastModified": 1663551060,
-        "narHash": "sha256-e2SR4cVx9p7aW/XnVsGsWZBplApA9ZJUjc0fejJhnYo=",
-        "owner": "nixos",
-        "repo": "nixpkgs",
-        "rev": "8a5b9ee7b7a2b38267c9481f5c629c015108ab0d",
-        "type": "github"
-      },
-      "original": {
-        "id": "nixpkgs",
-        "type": "indirect"
-      }
-    },
-    "root": {
-      "inputs": {
-        "fenix": "fenix",
-        "flake-utils": "flake-utils",
-        "nixpkgs": "nixpkgs_2"
-      }
-    },
-    "rust-analyzer-src": {
-      "flake": false,
-      "locked": {
-        "lastModified": 1687460085,
-        "narHash": "sha256-Npfu+4+KpgtZd/JX9wUaV3qP8dwbmoRd4s1NSehwyiE=",
-        "owner": "rust-lang",
-        "repo": "rust-analyzer",
-        "rev": "403433a35559962ad0df91c0ae85ab03e918ba54",
-        "type": "github"
-      },
-      "original": {
-        "owner": "rust-lang",
-        "ref": "nightly",
-        "repo": "rust-analyzer",
-        "type": "github"
-      }
-    },
-    "systems": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}

flake.nix

@@ -1,34 +0,0 @@
-{
-  inputs = { fenix.url = "github:nix-community/fenix"; };
-
-  outputs = { self, nixpkgs, flake-utils, fenix }:
-    flake-utils.lib.eachDefaultSystem (system:
-      let
-        pkgs = import nixpkgs {
-          inherit system;
-          overlays = [ fenix.overlays.default ];
-        };
-
-        toolchain = pkgs.fenix.default;
-
-        flakePkgs = rec { beng = pkgs.callPackage ./. { inherit toolchain; }; };
-      in rec {
-        packages = flake-utils.lib.flattenTree flakePkgs;
-        defaultPackage = packages.beng;
-
-        devShell = pkgs.mkShell {
-          inputsFrom = with packages; [ beng ];
-
-          packages = (with pkgs; [
-            cargo-watch
-            cargo-deny
-            cargo-edit
-            cargo-expand
-            pijul
-
-            # Get the nightly version of rustfmt so we can wrap comments
-            pkgs.fenix.default.rustfmt
-          ]) ++ (with toolchain; [ cargo clippy rustc rustfmt ]);
-        };
-      });
-}

rustfmt.toml

@@ -1,3 +1,2 @@
-max_width = 80
-tab_spaces = 2
+max_width = 100
 wrap_comments = true

src/ast.rs

@@ -1,125 +1,62 @@
 #[derive(Debug)]
 pub struct Program {
-  pub(crate) items: Vec<Item>,
-}
-
-/// Range
-#[derive(Debug)]
-pub struct Loc(usize, usize);
-
-impl Loc {
-  pub fn new(left: usize, right: usize) -> Self {
-    Loc(left, right)
-  }
-}
-
-// ===============================================
-// Items
-
-#[derive(Debug)]
-pub struct Item {
-  pub(crate) kind: ItemKind,
-  pub(crate) loc: Loc,
+    pub decls: Vec<Decl>,
 }
 
 #[derive(Debug)]
-pub enum ItemKind {
-  Import(Import),
-  FuncDef(FuncDef),
-  StructDef(StructDef),
-}
-
-// ===============================================
-// Import
-
-#[derive(Debug)]
-pub struct Import {
-  pub(crate) from: String,
-  pub(crate) items: ImportItem,
+pub enum Decl {
+    Mod(Mod),
+    Func(Func),
 }
 
 #[derive(Debug)]
-pub enum ImportItem {
-  SelfItem(Option<String>),
-  Item(String, Option<String>),
-  Module(String, Vec<ImportItem>),
-}
-
-// ===============================================
-// Functions
-
-#[derive(Debug)]
-pub struct FuncDef {
-  pub(crate) name: Option<String>,
-  pub(crate) body: Expr,
-  pub(crate) loc: Loc,
-}
-
-// ===============================================
-// Structs
-
-#[derive(Debug)]
-pub struct StructDef {
-}
-
-// ===============================================
-// Expr
-
-#[derive(Debug)]
-pub struct Expr {
-  pub(crate) kind: ExprKind,
-  pub(crate) loc: Loc,
+pub struct Mod {
+    pub name: Ident,
+    pub decls: Vec<Decl>,
 }
 
 #[derive(Debug)]
-pub enum ExprKind {
-  // Literals / primitives
-  Literal(Literal),
-
-  // More copmlex expressionsj
-  BinOp(Box<Expr>, BinOp, Box<Expr>),
-
-  Sequence(Sequence),
-  Paren(Box<Expr>),
+pub struct Func {
+    pub name: Ident,
+    pub args: Vec<Arg>,
+    pub stmts: Vec<Stmt>,
+    pub ret: Option<Expr>,
 }
 
 #[derive(Debug)]
-pub struct Sequence {
-  pub(crate) stmts: Vec<Stmt>,
-  pub(crate) inner: Box<Expr>,
-}
-
-// Stmts
-
-#[derive(Debug)]
-pub struct Stmt {
-  pub(crate) kind: StmtKind,
-  pub(crate) loc: Loc,
+pub struct Arg {
+    pub name: Ident,
+    pub ty: Type,
 }
 
 #[derive(Debug)]
-pub enum StmtKind {
+pub enum Stmt {
     Expr(Expr),
-}
-
-// ===============================================
-// Literals
-
-#[derive(Debug)]
-pub struct Literal {
-  pub(crate) kind: LiteralKind,
-  pub(crate) loc: Loc,
+    Return(Expr),
+    Let(Ident, Expr),
 }
 
 #[derive(Debug)]
-pub enum LiteralKind {
-  Int(u64),
+pub enum Expr {
+    Seq(Vec<Stmt>, Box<Expr>),
+    FuncCall(Ident),
+    Var(Ident),
+    Lit(Lit),
 }
 
-// ===============================================
-// Random shit
-
 #[derive(Debug)]
-pub enum BinOp {
-  Plus,
+pub enum Lit {
+    Unit,
+    Int(i64),
 }
+
+#[derive(Debug)]
+pub enum Type {
+    Unit,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub struct Ident(pub String);
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub struct Path(pub Vec<Ident>);

src/codegen.rs

@@ -0,0 +1,46 @@
+use anyhow::Result;
+use cranelift::prelude::*;
+use cranelift_module::{Linkage, Module};
+
+use crate::ast::{Decl, Program};
+
+impl Program {
+    pub fn codegen(&self, mut module: impl Module) -> Result<()> {
+        let mut ctx = module.make_context();
+
+        for decl in self.decls.iter() {
+            match decl {
+                Decl::Func(func) => {
+                    let mut builder_ctx = FunctionBuilderContext::new();
+                    let mut builder = FunctionBuilder::new(&mut ctx.func, &mut builder_ctx);
+                    let entry_block = builder.create_block();
+                    builder.append_block_params_for_function_params(entry_block);
+                    builder.switch_to_block(entry_block);
+                    builder.seal_block(entry_block);
+
+                    let int = module.target_config().pointer_type();
+                    let val = builder.ins().iconst(int, 12345);
+                    builder.ins().return_(&[val]);
+
+                    builder.finalize();
+                    ctx.func.signature.returns.push(AbiParam::new(int));
+
+                    let func_id = module.declare_function(
+                        &func.name.0,
+                        Linkage::Export,
+                        &ctx.func.signature,
+                    )?;
+                    module.define_function(
+                        func_id,
+                        &mut ctx,
+                        &mut codegen::binemit::NullTrapSink {},
+                    )?;
+                    module.clear_context(&mut ctx);
+                }
+                _ => {}
+            }
+        }
+
+        Ok(())
+    }
+}

src/grammar.lalrpop

@@ -1,67 +0,0 @@
-use crate::ast::*;
-
-grammar;
-
-pub Program: Program = <items:Item*> => Program {
-  items,
-};
-
-Item: Item = {
-  <left:@L> <kind:ItemKind> <right:@R> =>
-    Item { kind, loc: Loc::new(left, right) },
-};
-
-ItemKind: ItemKind = {
-  "fn" <funcdef:FuncDef> => ItemKind::FuncDef(funcdef),
-};
-
-FuncDef: FuncDef =
-  <left:@L> <ident:Ident> <body:BlockExpr> <right:@R> => FuncDef {
-    name: Some(ident),
-    body,
-    loc: Loc::new(left, right),
-  };
-
-Expr: Expr =
-  <left:@L> <kind:ExprKind> <right:@R> => Expr {
-    kind,
-    loc: Loc::new(left, right),
-  };
-
-ExprKind: ExprKind = {
-  <literal:Literal> => ExprKind::Literal(literal),
-  "(" <expr:Expr> ")" => ExprKind::Paren(Box::new(expr)),
-};
-
-BlockExpr: Expr =
-  <left:@L> "{" <stmts:StmtSemi*> <expr:Expr> "}" <right:@R> => Expr {
-    kind: ExprKind::Sequence(Sequence {
-      stmts,
-      inner: Box::new(expr),
-    }),
-    loc: Loc::new(left, right),
-  };
-
-StmtSemi: Stmt =
-  <left:@L> <kind:StmtKind> <right:@R> ";" => Stmt {
-    kind,
-    loc: Loc::new(left, right),
-  };
-
-StmtKind: StmtKind = {
-  <expr:Expr> => StmtKind::Expr(expr),
-};
-
-Literal: Literal =
-  <left:@L> <kind:LiteralKind> <right:@R> => Literal {
-    kind,
-    loc: Loc::new(left, right),
-  };
-
-LiteralKind: LiteralKind = {
-  r"[0-9]+" => LiteralKind::Int(<>.parse().unwrap()),
-};
-
-// Random shit
-
-Ident: String = r"[A-Za-z_]+" => <>.to_owned();

src/main.rs

@@ -1,38 +1,70 @@
 pub mod ast;
-pub mod typeck;
+pub mod codegen;
+pub mod name_res;
+pub mod parser;
+pub mod type_check;
+pub mod utils;
 
-use std::{path::PathBuf, fs::File, io::Read};
+use std::fs::{File, OpenOptions};
+use std::io::{Read, Write};
+use std::path::PathBuf;
 
-use clap::Parser;
 use anyhow::Result;
-use lalrpop_util::lalrpop_mod;
+use cranelift::prelude::*;
+use structopt::StructOpt;
 
-lalrpop_mod!(pub grammar);
+use crate::name_res::Namespaces;
 
-#[derive(Debug, Parser)]
+#[derive(StructOpt)]
 struct Opt {
-  input_file: PathBuf,
+    file: PathBuf,
+    #[structopt(name = "out", short = "o", default_value = "a.out")]
+    out: PathBuf,
 }
 
 fn main() -> Result<()> {
-  let opt = Opt::parse();
+    let opt = Opt::from_args();
 
     let contents = {
-    let mut file = File::open(&opt.input_file)?;
-    let mut string = String::new();
-    file.read_to_string(&mut string)?;
-    string
+        let mut file = File::open(&opt.file)?;
+        let mut contents = String::new();
+        file.read_to_string(&mut contents)?;
+        contents
     };
 
-  let parser = grammar::ProgramParser::new();
+    let parsed = parser::parse(&contents)?;
 
-  let tree = parser.parse(&contents);
+    let namespaces = Namespaces::create(parsed);
+    let resolved = namespaces.name_resolution();
+    println!("resolved: {:?}", resolved);
 
-  println!("tree: {tree:?}");
+    let isa = {
+        use std::str::FromStr;
+        use target_lexicon::triple;
+        let builder = settings::builder();
+        let flags = settings::Flags::new(builder);
+        isa::lookup(triple!("x86_64-unknown-linux-gnu"))?.finish(flags)
+    };
+    use cranelift_object::{ObjectBuilder, ObjectModule};
+    let libcall_names = cranelift_module::default_libcall_names();
+    let builder = ObjectBuilder::new(isa, "OSU", libcall_names)?;
+    let mut module = ObjectModule::new(builder);
 
-  // TODO: Distill tree into rules
+    // parsed.codegen(&mut module)?;
 
-  // TODO: Type-checking
+    let product = module.finish();
+    let out = product.emit()?;
+    {
+        let mut open_opt = OpenOptions::new();
+        #[cfg(target_os = "linux")]
+        {
+            use std::os::unix::fs::OpenOptionsExt;
+            // open_opt.mode(0o755);
+        }
+        open_opt.create(true).write(true);
+        let mut file = open_opt.open(&opt.out)?;
+        file.write_all(&out)?;
+    }
 
     Ok(())
 }

src/name_res.rs

@@ -0,0 +1,152 @@
+//! Name resolution
+//! ===
+//!
+//! This module deals with name resolution, ultimately going from a bunch of
+//! different files into a single expression tree ready for type-checking.
+
+use std::collections::{HashMap, HashSet};
+
+use petgraph::{algo, graphmap::DiGraphMap};
+
+use crate::ast::*;
+use crate::utils::Id;
+
+type HDecls = HashMap<Id, HDecl>;
+type Graph = DiGraphMap<Id, ()>;
+type Scopes = Vec<HashSet<String>>;
+
+#[derive(Debug)]
+pub enum HDecl {
+    Func(HFunc),
+}
+
+#[derive(Debug)]
+pub struct HFunc {}
+
+#[derive(Debug)]
+pub struct HExpr {}
+
+#[derive(Debug)]
+pub struct HStmt {}
+
+#[derive(Debug)]
+pub struct HType {}
+
+#[derive(Debug)]
+pub struct Namespaces {
+    funcs: HashMap<Id, Func>,
+    types: HashMap<Id, Type>,
+
+    hfuncs: HashMap<Id, HFunc>,
+
+    func_names: HashMap<String, Id>,
+    type_names: HashMap<String, Id>,
+}
+
+#[derive(Debug)]
+pub struct NamesResolved {
+    pub decls: HashMap<Id, HDecl>,
+    pub visit_order: Vec<HashSet<Id>>,
+}
+
+impl Namespaces {
+    pub fn create(program: Program) -> Self {
+        let mut funcs = HashMap::new();
+        let types = HashMap::new();
+        let mut func_names = HashMap::new();
+        let type_names = HashMap::new();
+
+        for decl in program.decls {
+            match decl {
+                Decl::Func(func) => {
+                    let id = Id::default();
+                    func_names.insert(func.name.0.clone(), id);
+                    funcs.insert(id, func);
+                }
+                Decl::Mod(_mod) => {}
+            }
+        }
+
+        Namespaces {
+            funcs,
+            types,
+            hfuncs: HashMap::new(),
+            func_names,
+            type_names,
+        }
+    }
+
+    pub fn name_resolution(&self) -> NamesResolved {
+        let mut hdecls = HashMap::new();
+        let mut graph = Graph::new();
+
+        for (id, func) in self.funcs.iter() {
+            walk_func(&mut hdecls, &mut graph, &self, *id, func);
+        }
+
+        let mut visit_order = Vec::new();
+        let scc = algo::tarjan_scc(&graph);
+        for group in scc.iter() {
+            let set = group.iter().cloned().collect();
+            visit_order.push(set);
+        }
+
+        NamesResolved {
+            decls: hdecls,
+            visit_order,
+        }
+    }
+}
+
+fn walk_func(h: &mut HDecls, g: &mut Graph, n: &Namespaces, src: Id, f: &Func) {
+    let mut scopes = Vec::new();
+    scopes.push(HashSet::new());
+    for s in f.stmts.iter() {
+        walk_stmt(g, n, src, &mut scopes, s);
+    }
+    if let Some(ret) = &f.ret {
+        walk_expr(g, n, src, &mut scopes, ret);
+    }
+    scopes.pop();
+    assert!(scopes.is_empty());
+
+    let func = HFunc {};
+    h.insert(src, HDecl::Func(func));
+}
+
+fn walk_stmt(g: &mut Graph, n: &Namespaces, src: Id, sc: &mut Scopes, s: &Stmt) {
+    match s {
+        Stmt::Let(_, e) | Stmt::Expr(e) | Stmt::Return(e) => walk_expr(g, n, src, sc, e),
+    }
+}
+
+fn walk_expr(g: &mut Graph, n: &Namespaces, src: Id, sc: &mut Scopes, e: &Expr) {
+    match e {
+        Expr::FuncCall(id) | Expr::Var(id) => {
+            let id = &id.0;
+            let mut found = false;
+            for scope in sc.iter().rev() {
+                if scope.contains(id) {
+                    found = true;
+                    break;
+                }
+            }
+            if !found {
+                if let Some(target_id) = n.func_names.get(id) {
+                    g.add_node(src);
+                    g.add_node(*target_id);
+                    g.add_edge(src, *target_id, ());
+                }
+            }
+        }
+        Expr::Seq(stmts, e) => {
+            sc.push(HashSet::new());
+            for s in stmts {
+                walk_stmt(g, n, src, sc, s);
+            }
+            walk_expr(g, n, src, sc, e);
+            sc.pop();
+        }
+        Expr::Lit(_) => {}
+    }
+}

src/parser.lalrpop

@@ -0,0 +1,59 @@
+use crate::ast::*;
+
+grammar;
+
+pub Program: Program = {
+    <decls:Decls> => { Program { decls } }
+};
+
+Decls: Vec<Decl> = Decl*;
+
+Decl: Decl = {
+    "fn" <name:Ident> "(" <args:Sep<Arg, ",">> ")" "{" <stmts:Stmt*> <ret:Expr> "}" => { Decl::Func(Func{ name, args, stmts, ret: Some(ret), }) },
+    "fn" <name:Ident> "(" <args:Sep<Arg, ",">> ")" "{" <stmts:Stmt*> "}" => { Decl::Func(Func{ name, args, stmts, ret: None, }) },
+};
+
+Arg: Arg = <name:Ident> ":" <ty:Type> => Arg { name, ty };
+
+Stmt: Stmt = {
+    <expr:Expr> ";" => Stmt::Expr(expr),
+    "let" <name:Ident> "=" <expr:Expr> ";" => Stmt::Let(name, expr),
+    "return" <expr:Expr> ";" => Stmt::Return(expr),
+};
+
+BlockExpr: Expr = "{" <stmts:Stmt*> <expr:Expr> "}" => Expr::Seq(stmts, Box::new(expr));
+
+Expr: Expr = {
+    <name:Ident> "(" ")" => Expr::FuncCall(name),
+    Ident => Expr::Var(<>),
+    Lit => Expr::Lit(<>),
+};
+
+Lit: Lit = {
+    "(" ")" => Lit::Unit,
+    Int => Lit::Int(<>),
+};
+
+Type: Type = {
+    "(" ")" => Type::Unit,
+};
+
+//
+
+Ident: Ident = r"[A-Za-z][A-Za-z0-9_]*|_[A-Za-z0-9_]+" => Ident(<>.to_owned());
+Int: i64 = r"[0-9]+" => <>.parse::<i64>().unwrap();
+
+//
+
+Sep<T, D>: Vec<T> = {
+    <v:Sep1<T, D>*> <e:T?> => match e {
+        None => v,
+        Some(e) => {
+            let mut v = v;
+            v.push(e);
+            v
+        }
+    }
+};
+
+Sep1<T, D>: T = <t:T> D => t;

src/parser.rs

@@ -0,0 +1,17 @@
+use anyhow::Result;
+
+use crate::ast::Program;
+
+mod parser {
+    #![allow(unused_braces)]
+    use lalrpop_util::lalrpop_mod;
+    lalrpop_mod!(parser);
+    pub use self::parser::*;
+}
+
+pub fn parse(s: impl AsRef<str>) -> Result<Program> {
+    let s = s.as_ref().to_owned();
+    let parser = parser::ProgramParser::new();
+    let res = parser.parse(&s).unwrap();
+    Ok(res)
+}

src/type_check.rs

@@ -0,0 +1,6 @@
+//! Type checking
+//! ===
+//!
+//! This module implements a Hindley-Milner based type checker.
+
+pub fn type_check() {}

src/typeck.rs

@@ -1,4 +0,0 @@
-use crate::ast::Program;
-
-pub fn check(ast: Program) {
-}

src/utils.rs

@@ -0,0 +1,26 @@
+use std::sync::Arc;
+
+use parking_lot::Mutex;
+
+use lazy_static::lazy_static;
+
+lazy_static! {
+    static ref N: Arc<Mutex<usize>> = Arc::new(Mutex::new(0));
+}
+
+/// An Id is a uniquely generated value, whose implementation is opaque.
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Id(usize);
+
+impl Default for Id {
+    fn default() -> Self {
+        Id(gen_int())
+    }
+}
+
+fn gen_int() -> usize {
+    let mut n = N.lock();
+    let res = *n;
+    *n += 1;
+    res
+}

traits

@@ -0,0 +1,13 @@
+trait Foo {
+    fn foo();
+}
+
+struct Bar impls Foo {
+
+}
+
+fn test(f: impl Foo) {
+}
+
+x = Bar {}
+test(x)