chewker done ^w^

Cargo.lock

@@ -2,6 +2,97 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "diff"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56254986775e3233ffa9c4d7d3faaf6d36a2c09d30b20687e9f88bc8bafc16c8"
+
+[[package]]
+name = "getrandom"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4567c8db10ae91089c99af84c68c38da3ec2f087c3f82960bcdbf3656b6f4d7"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.155"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "97b3888a4aecf77e811145cadf6eef5901f4782c53886191b2f693f24761847c"
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b40af805b3121feab8a3c29f04d8ad262fa8e0561883e7653e024ae4479e6de"
+
+[[package]]
+name = "pretty_assertions"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af7cee1a6c8a5b9208b3cb1061f10c0cb689087b3d8ce85fb9d2dd7a29b6ba66"
+dependencies = [
+ "diff",
+ "yansi",
+]
+
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
+
+[[package]]
+name = "yansi"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09041cd90cf85f7f8b2df60c646f853b7f535ce68f85244eb6731cf89fa498ec"
+
 [[package]]
 name = "yapping"
 version = "0.1.0"
+dependencies = [
+ "pretty_assertions",
+ "rand",
+]

Cargo.toml

@@ -6,3 +6,5 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+pretty_assertions = "1.4.0"
+rand = "0.8.5"

src/checked.rs

@@ -2,6 +2,7 @@
 pub struct Node {
     pub kind: NodeKind,
     pub typ: Type,
+    pub table_id: usize,
 }
 
 #[derive(Clone, PartialEq, Debug)]
@@ -36,7 +37,7 @@ pub enum NodeKind {
     Fn {
         subject: Box<Node>,
         params: Vec<Node>,
-        return_typ: Box<Node>,
+        return_typ: Type,
         body: Box<Node>,
     },
     Return {

src/checker.rs

@@ -1,79 +1,130 @@
 #![allow(unused_variables)]
 
+use rand::random;
+
 use crate::{
     checked::{Node, NodeKind, Type},
-    hash::hash,
     itertewls::Itertewls,
     parsed,
     sym::Syms,
+    util::hash,
 };
 
-pub struct Checker {}
+pub trait IdGen {
+    fn new() -> Self;
+    fn gen(&mut self) -> u64;
+}
 
+pub struct RandIdGen;
+impl IdGen for RandIdGen {
+    fn new() -> Self {
+        Self
+    }
+    fn gen(&mut self) -> u64 {
+        random()
+    }
+}
+
+pub struct Checker<FnIdGen: IdGen = RandIdGen> {
+    syms: Syms,
+    fn_id_gen: FnIdGen,
+}
 impl Checker {
     pub fn new() -> Self {
-        Self {}
+        Self {
+            syms: Syms::new(),
+            fn_id_gen: RandIdGen::new(),
+        }
+    }
+}
+
+impl<FnIdGen: IdGen> Checker<FnIdGen> {
+    pub fn new_with_fn_id_gen() -> Self {
+        Self {
+            syms: Syms::new(),
+            fn_id_gen: FnIdGen::new(),
+        }
     }
 
-    pub fn check(&mut self, ast: &Vec<parsed::Node>) -> Vec<Node> {
+    pub fn check(&mut self, ast: &[parsed::Node]) -> Vec<Node> {
-        let mut syms = Syms::new();
+        self.fn_scan(ast);
-        ast.into_iter()
+        ast.iter().map(|stmt| self.check_expr(stmt)).collect()
-            .map(|stmt| self.check_expr(stmt, &mut syms))
-            .collect()
     }
 
-    fn fn_scan<'syms>(
+    fn fn_scan(&mut self, ast: &[parsed::Node]) {
-        &mut self,
-        ast: &Vec<parsed::Node>,
-        syms: &mut Syms<'syms>,
-    ) -> Result<(), ()> {
         for node in ast {
-            match node {
+            if let parsed::Node::Fn {
-                parsed::Node::Fn {
+                subject,
-                    subject,
+                params,
-                    params,
+                return_typ,
-                    return_typ,
+                body,
-                    body,
+            } = node
-                } => {
+            {
-                    let params = params.into_iter().map(|param| {
+                let Ok(params) = self.fn_scan_params(params) else {
-                        let parsed::Node::Param { subject, typ } = param else { unreachable!() };
+                    continue;
-                        let parsed::Node::Id(id) = subject.as_ref() else { unreachable!() };
+                };
-                        let typ = self.check_type(typ.as_ref().ok_or(())?);
-                        Ok((*id, self.node(NodeKind::Param { subject: Box::new(self.node(NodeKind::Id(*id), Type::Unit)), typ: Some(typ) }, Type::Unit)))
-                    }).collect::<Result<Vec<_>, _>>()?;
 
-                    if let Some(id) = params.iter().map(|(id, _)| *id).find_first_duplicate() {
+                if let Some(id) = params.iter().map(|(id, _)| *id).find_first_duplicate() {
-                        self.error("redefinition param");
+                    self.error("redefinition param");
-                        return Err(());
+                    continue;
-                    }
-
-                    let parsed::Node::Id(id) = subject.as_ref() else { unreachable!() };
-
-                    if syms.defined_locally(*id) {
-                        self.error("redefinition fn");
-                        return Err(());
-                    }
-                    //syms.define(*id, typ.clone());
                 }
-                _ => {}
+
+                let params = params.into_iter().map(|(_, param)| param).collect();
+
+                let parsed::Node::Id(id) = subject.as_ref() else { unreachable!() };
+
+                if self.syms.defined_locally(*id) {
+                    self.error("redefinition fn");
+                    continue;
+                }
+
+                let return_typ = self.check_type(return_typ);
+
+                let typ = Type::Fn {
+                    id: self.fn_id_gen.gen(),
+                    params,
+                    return_typ: Box::new(return_typ),
+                };
+
+                self.syms.define(*id, typ.clone());
             }
         }
-        Ok(())
     }
 
-    fn check_expr<'syms>(&mut self, node: &parsed::Node, syms: &mut Syms<'syms>) -> Node {
+    fn fn_scan_params(&self, params: &[parsed::Node]) -> Result<Vec<(u64, Node)>, ()> {
+        params
+            .iter()
+            .map(|param| {
+                let parsed::Node::Param { subject, typ } = param else { unreachable!() };
+                let parsed::Node::Id(id) = subject.as_ref() else { unreachable!() };
+                let typ = self.check_type(typ.as_ref().ok_or(())?);
+                Ok((
+                    *id,
+                    self.node(
+                        NodeKind::Param {
+                            subject: Box::new(self.node(NodeKind::Id(*id), Type::Unit)),
+                            typ: Some(typ),
+                        },
+                        Type::Unit,
+                    ),
+                ))
+            })
+            .collect::<Result<Vec<_>, _>>()
+    }
+
+    fn check_expr(&mut self, node: &parsed::Node) -> Node {
         match node {
             parsed::Node::Error => self.node(NodeKind::Error, Type::Unit),
             parsed::Node::Id(id) => {
-                let Some(sym) = syms.get(*id) else {
+                let Some(sym) = self.syms.get(*id) else {
                     self.error("undefined >~<");
                     return self.node(NodeKind::Error, Type::Error);
                 };
-                self.node(NodeKind::Id(*id), sym.typ)
+                self.node(NodeKind::Id(*id), sym.typ.clone())
             }
             parsed::Node::Int(value) => self.node(
                 NodeKind::Int(*value),
-                if *value as i32 > i32::MAX {
+                if *value > i32::MAX as i64 {
                     Type::U32
                 } else {
                     Type::I32
@@ -81,16 +132,17 @@ impl Checker {
             ),
             parsed::Node::String(value) => self.node(NodeKind::String(value.clone()), Type::String),
             parsed::Node::Group(expr) => {
-                let expr = self.check_expr(expr, syms);
+                let expr = self.check_expr(expr);
                 let typ = expr.typ.clone();
                 self.node(NodeKind::Group(Box::new(expr)), typ)
             }
             parsed::Node::Block(stmts) => {
-                let mut child_syms = syms.child();
+                self.syms.enter_scope();
                 let stmts = stmts
-                    .into_iter()
+                    .iter()
-                    .map(|stmt| self.check_expr(stmt, &mut child_syms))
+                    .map(|stmt| self.check_expr(stmt))
                     .collect::<Vec<_>>();
+                self.syms.leave_scope().unwrap();
                 let typ = stmts
                     .last()
                     .map(|stmt| stmt.typ.clone())
@@ -98,11 +150,11 @@ impl Checker {
                 self.node(NodeKind::Block(stmts), typ)
             }
             parsed::Node::Call { subject, args } => {
-                let subject = Box::new(self.check_expr(subject, syms));
+                let subject = Box::new(self.check_expr(subject));
 
                 let args = args
-                    .into_iter()
+                    .iter()
-                    .map(|arg| self.check_expr(arg, syms))
+                    .map(|arg| self.check_expr(arg))
                     .collect::<Vec<_>>();
                 let typ = 'br: {
                     match subject.typ.clone() {
@@ -139,11 +191,9 @@ impl Checker {
                 truthy,
                 falsy,
             } => {
-                let cond = Box::new(self.check_expr(cond, syms));
+                let cond = Box::new(self.check_expr(cond));
-                let truthy = Box::new(self.check_expr(truthy, syms));
+                let truthy = Box::new(self.check_expr(truthy));
-                let falsy = falsy
+                let falsy = falsy.as_ref().map(|block| Box::new(self.check_expr(block)));
-                    .as_ref()
-                    .map(|block| Box::new(self.check_expr(block, syms)));
                 let typ = 'br: {
                     match falsy.as_ref().map(|block| block.typ.clone()) {
                         Some(falsy_typ) => {
@@ -166,14 +216,15 @@ impl Checker {
                 )
             }
             parsed::Node::Loop { body } => {
-                let body = Box::new(self.check_expr(body, &mut syms.child()));
+                self.syms.enter_scope();
+                let body = Box::new(self.check_expr(body));
                 let typ = body.typ.clone();
                 self.node(NodeKind::Loop { body }, typ)
             }
             parsed::Node::Break => self.node(NodeKind::Break, Type::Unit),
             parsed::Node::Assign { subject, value } => {
-                let subject = Box::new(self.check_expr(subject, syms));
+                let subject = Box::new(self.check_expr(subject));
-                let value = Box::new(self.check_expr(value, syms));
+                let value = Box::new(self.check_expr(value));
 
                 let typ = if !self.compatible(&subject.typ, &value.typ) {
                     self.error("incompatible types #3");
@@ -191,7 +242,7 @@ impl Checker {
                     _ => unreachable!(),
                 };
 
-                let value = Box::new(self.check_expr(value, syms));
+                let value = Box::new(self.check_expr(value));
                 let typ = value.typ.clone();
 
                 if subject_typ
@@ -205,11 +256,11 @@ impl Checker {
 
                 let subject = match subject.as_ref() {
                     parsed::Node::Id(id) => {
-                        if syms.defined_locally(*id) {
+                        if self.syms.defined_locally(*id) {
                             self.error("redefinition");
                             return self.node(NodeKind::Error, Type::Error);
                         }
-                        syms.define(*id, typ.clone());
+                        self.syms.define(*id, typ.clone());
                         Box::new(self.node(
                             NodeKind::Param {
                                 subject: Box::new(self.node(NodeKind::Id(*id), Type::Unit)),
@@ -225,16 +276,53 @@ impl Checker {
             }
             parsed::Node::Fn {
                 subject,
-                params,
+                params: _,
-                return_typ,
+                return_typ: _,
                 body,
             } => {
-                todo!("symbol lookup");
+                let parsed::Node::Id(id) = subject.as_ref() else { unreachable!() };
+
+                let Some(sym) = self.syms.get(*id).cloned() else {
+                    // rejected in fn scanner
+                    return self.node(NodeKind::Error,Type::Error);
+                };
+
+                let Type::Fn { id: fn_id, params, return_typ } = sym.typ else {
+                    self.error("redefintion");
+                    return self.node(NodeKind::Error,Type::Error);
+                };
+
+                self.syms.enter_scope();
+
+                for param in &params {
+                    let NodeKind::Param {
+                        ref subject,
+                        typ: Some(ref typ),
+                    } = param.kind else { unreachable!() };
+                    let NodeKind::Id(id) = subject.kind else { unreachable!() };
+                    self.syms.define(id, typ.clone());
+                }
+
+                let body = Box::new(self.check_expr(body));
+
+                if !self.compatible(&return_typ, &body.typ) {
+                    self.error("return type violated");
+                }
+
+                self.syms.leave_scope().unwrap();
+
+                self.node(
+                    NodeKind::Fn {
+                        subject: Box::new(self.node(NodeKind::Id(*id), Type::Unit)),
+                        params,
+                        return_typ: *return_typ,
+                        body,
+                    },
+                    Type::Unit,
+                )
             }
             parsed::Node::Return { value } => {
-                let value = value
+                let value = value.as_ref().map(|value| Box::new(self.check_expr(value)));
-                    .as_ref()
-                    .map(|value| Box::new(self.check_expr(value, syms)));
                 let typ = value
                     .as_ref()
                     .map(|value| value.typ.clone())
@@ -266,7 +354,11 @@ impl Checker {
     }
 
     fn node(&self, kind: NodeKind, typ: Type) -> Node {
-        Node { kind, typ }
+        Node {
+            kind,
+            typ,
+            table_id: self.syms.table_id(),
+        }
     }
 
     fn error<S: Into<String>>(&mut self, msg: S) {
@@ -278,10 +370,24 @@ impl Checker {
 #[test]
 fn test_checker() {
     use crate::parser::Parser;
-    use NodeKind::{Block, Id, Int, Let, Param};
+    use pretty_assertions::assert_eq;
+    use NodeKind::{Block, Call, Error, Fn, Id, Int, Let, Param, Return};
     use Type::{Unit, I32};
 
-    let check = |text| Checker::new().check(&Parser::new(text).parse());
+    struct SeqIdGen(u64);
+    impl IdGen for SeqIdGen {
+        fn new() -> Self {
+            Self(0)
+        }
+
+        fn gen(&mut self) -> u64 {
+            let v = self.0;
+            self.0 += 1;
+            v
+        }
+    }
+
+    let check = |text| Checker::<SeqIdGen>::new_with_fn_id_gen().check(&Parser::new(text).parse());
 
     assert_eq!(
         check("let a = 5; a;"),
@@ -292,26 +398,69 @@ fn test_checker() {
                         kind: Param {
                             subject: Box::new(Node {
                                 kind: Id(hash("a")),
-                                typ: Unit
+                                typ: Unit,
+                                table_id: 0,
                             }),
                             typ: Some(Unit)
                         },
-                        typ: Unit
+                        typ: Unit,
+                        table_id: 0,
                     }),
                     value: Box::new(Node {
                         kind: Int(5),
-                        typ: I32
+                        typ: I32,
+                        table_id: 0,
                     })
                 },
-                typ: I32
+                typ: I32,
+                table_id: 0,
             },
             Node {
                 kind: Id(hash("a")),
-                typ: I32
+                typ: I32,
+                table_id: 0,
             }
         ]
     );
 
+    assert_eq!(
+        check("let a = 5; { a; }"),
+        vec![
+            Node {
+                kind: Let {
+                    subject: Box::new(Node {
+                        kind: Param {
+                            subject: Box::new(Node {
+                                kind: Id(hash("a")),
+                                typ: Unit,
+                                table_id: 0,
+                            }),
+                            typ: Some(Unit)
+                        },
+                        typ: Unit,
+                        table_id: 0,
+                    }),
+                    value: Box::new(Node {
+                        kind: Int(5),
+                        typ: I32,
+                        table_id: 0,
+                    })
+                },
+                typ: I32,
+                table_id: 0,
+            },
+            Node {
+                kind: Block(vec![Node {
+                    kind: Id(hash("a")),
+                    typ: I32,
+                    table_id: 1,
+                },]),
+                typ: I32,
+                table_id: 0,
+            },
+        ]
+    );
+
     assert_eq!(
         check("let a = 5; a; { a; let b = 5; b; } a; b;"),
         vec![
@@ -321,28 +470,34 @@ fn test_checker() {
                         kind: Param {
                             subject: Box::new(Node {
                                 kind: Id(hash("a")),
-                                typ: Unit
+                                typ: Unit,
+                                table_id: 0,
                             }),
                             typ: Some(Unit)
                         },
-                        typ: Unit
+                        typ: Unit,
+                        table_id: 0,
                     }),
                     value: Box::new(Node {
                         kind: Int(5),
-                        typ: I32
+                        typ: I32,
+                        table_id: 0,
                     })
                 },
-                typ: I32
+                typ: I32,
+                table_id: 0,
             },
             Node {
                 kind: Id(hash("a")),
-                typ: I32
+                typ: I32,
+                table_id: 0,
             },
             Node {
                 kind: Block(vec![
                     Node {
                         kind: Id(hash("a")),
-                        typ: I32
+                        typ: I32,
+                        table_id: 1,
                     },
                     Node {
                         kind: Let {
@@ -350,34 +505,92 @@ fn test_checker() {
                                 kind: Param {
                                     subject: Box::new(Node {
                                         kind: Id(hash("b")),
-                                        typ: Unit
+                                        typ: Unit,
+                                        table_id: 1,
                                     }),
                                     typ: Some(Unit)
                                 },
-                                typ: Unit
+                                typ: Unit,
+                                table_id: 1,
                             }),
                             value: Box::new(Node {
                                 kind: Int(5),
-                                typ: I32
+                                typ: I32,
+                                table_id: 1,
                             })
                         },
-                        typ: I32
+                        typ: I32,
+                        table_id: 1,
                     },
                     Node {
                         kind: Id(hash("b")),
-                        typ: I32
+                        typ: I32,
+                        table_id: 1,
                     }
                 ]),
-                typ: I32
+                typ: I32,
+                table_id: 0,
             },
             Node {
                 kind: Id(hash("a")),
-                typ: I32
+                typ: I32,
+                table_id: 0,
             },
             Node {
-                kind: NodeKind::Error,
+                kind: Error,
-                typ: Type::Error
+                typ: Type::Error,
+                table_id: 0,
             }
         ]
     );
+
+    assert_eq!(
+        check("fn a() -> i32 { return 0; } \n a();"),
+        vec![
+            Node {
+                kind: Fn {
+                    subject: Box::new(Node {
+                        kind: Id(hash("a")),
+                        typ: Unit,
+                        table_id: 0,
+                    }),
+                    params: vec![],
+                    return_typ: I32,
+                    body: Box::new(Node {
+                        kind: Block(vec![Node {
+                            kind: Return {
+                                value: Some(Box::new(Node {
+                                    kind: Int(0),
+                                    typ: I32,
+                                    table_id: 2,
+                                }),),
+                            },
+                            typ: I32,
+                            table_id: 2,
+                        },],),
+                        typ: I32,
+                        table_id: 1,
+                    }),
+                },
+                typ: Unit,
+                table_id: 0,
+            },
+            Node {
+                kind: Call {
+                    subject: Box::new(Node {
+                        kind: Id(hash("a")),
+                        typ: Type::Fn {
+                            id: 0,
+                            params: vec![],
+                            return_typ: Box::new(I32)
+                        },
+                        table_id: 0
+                    }),
+                    args: vec![]
+                },
+                typ: I32,
+                table_id: 0,
+            },
+        ]
+    );
 }

src/lexer.rs

@@ -1,6 +1,6 @@
 use crate::{
-    hash::hash,
     token::{Token, TokenKind, TokenValue},
+    util::hash,
 };
 use std::{collections::HashMap, str::Chars};
 

src/main.rs

@@ -2,13 +2,13 @@
 
 mod checked;
 mod checker;
-mod hash;
 mod itertewls;
 mod lexer;
 mod parsed;
 mod parser;
 mod sym;
 mod token;
+mod util;
 
 fn main() {
     println!("Hello, world!");

src/parser.rs

@@ -205,7 +205,7 @@ impl<'a> Parser<'a> {
                     self.step();
                     let mut args = Vec::new();
                     match self.curr_kind() {
-                        None | Some(TokenKind::LParen) => {}
+                        None | Some(TokenKind::RParen) => {}
                         Some(_) => {
                             args.push(self.parse_expr());
                             while let Some(TokenKind::Comma) = self.curr_kind() {
@@ -378,7 +378,7 @@ impl<'a> Parser<'a> {
 
 #[test]
 fn test_parser() {
-    use crate::hash::hash;
+    use crate::util::hash;
     use Node::*;
 
     let parse = |text| Parser::new(text).parse();

src/sym.rs

@@ -9,40 +9,106 @@ pub struct Sym {
     pub typ: Type,
 }
 
-pub struct Syms<'syms> {
+#[derive(Debug)]
-    parent: Option<&'syms Syms<'syms>>,
+pub struct Syms {
-    map: HashMap<u64, Sym>,
+    tables: Vec<SymTable>,
+    current_id: usize,
 }
 
-impl<'syms> Syms<'syms> {
+impl Syms {
     pub fn new() -> Self {
         Self {
-            parent: None,
+            tables: vec![SymTable::new()],
-            map: HashMap::new(),
+            current_id: 0,
         }
     }
 
-    pub fn child(&'syms self) -> Self {
+    pub fn enter_scope(&mut self) {
-        Self {
+        let new_id = self.tables.len();
-            parent: Some(self),
+        self.tables.push(SymTable::from(self.current_id));
-            map: HashMap::new(),
+        self.current_id = new_id;
-        }
     }
 
-    pub fn get(&self, id: u64) -> Option<Sym> {
+    pub fn leave_scope(&mut self) -> Result<(), ()> {
-        if let Some(sym) = self.map.get(&id) {
+        let parent = self.tables[self.current_id].parent.ok_or(())?;
-            return Some(sym.clone());
+        self.current_id = parent;
-        }
+        Ok(())
-        if let Some(parent) = self.parent {
+    }
-            return parent.get(id);
+
+    pub fn get(&self, id: u64) -> Option<&Sym> {
+        self.get_rec(self.current_id, id)
+    }
+
+    fn get_rec(&self, table_id: usize, id: u64) -> Option<&Sym> {
+        if let Some(sym) = self.tables[table_id].get(id) {
+            return Some(sym);
         }
+        if let Some(parent_id) = self.tables[table_id].parent {
+            return self.get_rec(parent_id, id);
+        };
         None
     }
 
     pub fn defined_locally(&self, id: u64) -> bool {
+        self.tables[self.current_id].defined(id)
+    }
+
+    pub fn define(&mut self, id: u64, typ: Type) {
+        self.tables[self.current_id].define(id, typ);
+    }
+
+    pub fn table_id(&self) -> usize {
+        self.current_id
+    }
+
+    pub fn view(&self, table_id: usize) -> SymView {
+        SymView {
+            syms: self,
+            current_id: table_id,
+        }
+    }
+}
+
+pub struct SymView<'a> {
+    syms: &'a Syms,
+    current_id: usize,
+}
+
+impl<'a> SymView<'a> {
+    pub fn get(&self, id: u64) -> Option<&Sym> {
+        self.syms.get_rec(self.current_id, id)
+    }
+}
+
+#[derive(Debug)]
+struct SymTable {
+    map: HashMap<u64, Sym>,
+    parent: Option<usize>,
+}
+
+impl SymTable {
+    pub fn new() -> Self {
+        Self {
+            map: HashMap::new(),
+            parent: None,
+        }
+    }
+
+    pub fn from(parent: usize) -> Self {
+        Self {
+            map: HashMap::new(),
+            parent: Some(parent),
+        }
+    }
+
+    pub fn defined(&self, id: u64) -> bool {
         self.map.contains_key(&id)
     }
 
+    pub fn get(&self, id: u64) -> Option<&Sym> {
+        self.map.get(&id)
+    }
+
     pub fn define(&mut self, id: u64, typ: Type) {
         self.map.insert(id, Sym { id, typ });
     }