Giant overhaul, still doesn't work tho

This commit is contained in:
Michael Zhang 2022-04-06 06:20:47 -05:00
parent daaf859f81
commit c51de77269
Signed by: michael
GPG key ID: BDA47A31A3C8EE6B
8 changed files with 679 additions and 64 deletions

2
.gitignore vendored
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@ -3,3 +3,5 @@ result*
*.bc *.bc
*.ll *.ll
a.out

11
examples/conditions.e0 Normal file
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@ -0,0 +1,11 @@
fn main() -> int {
let x = 5;
if x < 3 {
return 3;
} else if x > 10 {
return 10;
} else {
return x;
}
}

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@ -1,4 +1,4 @@
use std::{collections::HashMap, marker::PhantomData}; use std::collections::HashMap;
use anyhow::Result; use anyhow::Result;
use inkwell::{ use inkwell::{
@ -6,31 +6,72 @@ use inkwell::{
context::Context, context::Context,
module::Module, module::Module,
types::{BasicMetadataTypeEnum, BasicTypeEnum, FunctionType}, types::{BasicMetadataTypeEnum, BasicTypeEnum, FunctionType},
values::{AnyValueEnum, BasicValueEnum, PointerValue}, values::{BasicValueEnum, FunctionValue, IntValue, PointerValue},
IntPredicate,
}; };
use super::{Decl, Expr, Stmt, Type}; use super::{Decl, ElseClause, Expr, ExprKind, IfElse, Op, Stmt, Type};
impl Expr { impl Expr<Type> {
fn into_llvm<'ctx>( fn into_llvm<'ctx>(
&self, &self,
context: &'ctx Context, context: &'ctx Context,
builder: &Builder, builder: &'ctx Builder,
env: &Env<'_, 'ctx>, env: &Env<'_, 'ctx>,
) -> Result<BasicValueEnum<'ctx>> { ) -> Result<BasicValueEnum<'ctx>> {
match self { let int_ty = context.i64_type();
Expr::Var(name) => { let bool_ty = context.bool_type();
match &self.kind {
ExprKind::Var(name) => {
let (_, value) = match env.lookup(&name) { let (_, value) = match env.lookup(&name) {
Some(v) => v, Some(v) => v,
None => bail!("Unbound name {name:?}"), None => bail!("Unbound name {name:?}"),
}; };
Ok(BasicValueEnum::PointerValue(*value)) Ok(builder.build_load(*value, ""))
} }
Expr::Int(n) => Ok(BasicValueEnum::IntValue( ExprKind::Int(n) => {
context.i64_type().const_int(*n as u64, false), Ok(BasicValueEnum::IntValue(int_ty.const_int(*n as u64, false)))
)), }
ExprKind::BinOp(left, op, right) => {
if !op.check_types(&left.ty, &right.ty) {
// TODO: detailed error message
bail!("Invalid types on operation.");
}
match op {
Op::LessThan => {
let left_val =
left.into_llvm(context, builder, env)?.into_int_value();
let right_val =
right.into_llvm(context, builder, env)?.into_int_value();
let result: IntValue = builder.build_int_compare(
IntPredicate::SLT,
left_val,
right_val,
"",
);
Ok(BasicValueEnum::IntValue(result))
}
Op::GreaterThan => {
let left_val =
left.into_llvm(context, builder, env)?.into_int_value();
let right_val =
right.into_llvm(context, builder, env)?.into_int_value();
let result: IntValue = builder.build_int_compare(
IntPredicate::SGT,
left_val,
right_val,
"",
);
Ok(BasicValueEnum::IntValue(result))
}
}
}
} }
} }
} }
@ -42,6 +83,8 @@ impl Type {
) -> BasicTypeEnum<'ctx> { ) -> BasicTypeEnum<'ctx> {
match self { match self {
Type::Int => BasicTypeEnum::IntType(context.i64_type()), Type::Int => BasicTypeEnum::IntType(context.i64_type()),
Type::Bool => BasicTypeEnum::IntType(context.bool_type()),
_ => panic!("Tried to convert a function type into a LLVM basic type"),
} }
} }
} }
@ -65,7 +108,7 @@ type EnvValue<'a, 'ctx> = (&'a Type, PointerValue<'ctx>);
#[derive(Default)] #[derive(Default)]
struct Env<'a, 'ctx> { struct Env<'a, 'ctx> {
parent: Option<Box<Env<'a, 'ctx>>>, parent: Option<&'a Env<'a, 'ctx>>,
local_type_map: HashMap<String, EnvValue<'a, 'ctx>>, local_type_map: HashMap<String, EnvValue<'a, 'ctx>>,
} }
@ -81,23 +124,72 @@ impl<'a, 'ctx> Env<'a, 'ctx> {
} }
} }
fn convert_lexical_block( fn convert_if_else(
context: &Context, context: &Context,
module: &Module,
builder: &Builder, builder: &Builder,
parent_env: Env, function: &FunctionValue,
stmts: impl AsRef<[Stmt]>, if_else: &IfElse<Type>,
env: &Env,
) -> Result<()> {
let success_branch = context.append_basic_block(*function, "success");
let fail_branch = context.append_basic_block(*function, "fail");
let exit_block = context.append_basic_block(*function, "exit");
let cond = if_else
.cond
.into_llvm(context, builder, env)?
.into_int_value();
builder.build_conditional_branch(cond, success_branch, fail_branch);
// build success branch
builder.position_at_end(success_branch);
convert_stmts(context, module, function, builder, env, &if_else.body)?;
// builder.build_unconditional_branch(exit_branch);
// build fail branch
builder.position_at_end(fail_branch);
match &if_else.else_clause {
Some(ElseClause::If(if_else2)) => {
println!("SUB-IF CLAUSE {if_else2:?}");
convert_if_else(context, module, builder, function, if_else2, env)?;
}
Some(ElseClause::Body(body)) => {
println!("STMTS {body:?}");
convert_stmts(context, module, function, builder, env, body)?;
}
None => {
println!("NOTHING");
}
}
builder.build_unconditional_branch(exit_block);
builder.position_at_end(exit_block);
Ok(())
}
fn convert_stmts(
context: &Context,
module: &Module,
function: &FunctionValue,
builder: &Builder,
parent_env: &Env,
stmts: impl AsRef<[Stmt<Type>]>,
) -> Result<()> { ) -> Result<()> {
let stmts = stmts.as_ref(); let stmts = stmts.as_ref();
let mut scope_env = Env { let mut scope_env = Env {
parent: Some(Box::new(parent_env)), parent: Some(parent_env),
..Default::default() ..Default::default()
}; };
for stmt in stmts.iter() { for stmt in stmts.iter() {
match stmt { match stmt {
Stmt::Let(name, ty, expr) => { Stmt::Let(name, _, expr) => {
let ty = &expr.ty;
let llvm_ty = ty.into_llvm_basic_type(context); let llvm_ty = ty.into_llvm_basic_type(context);
let alloca = builder.build_alloca(llvm_ty, name); // Empty variable name gets LLVM to generate a unique name
let alloca = builder.build_alloca(llvm_ty, "");
let expr_val = expr.into_llvm(context, builder, &scope_env)?; let expr_val = expr.into_llvm(context, builder, &scope_env)?;
builder.build_store(alloca, expr_val); builder.build_store(alloca, expr_val);
@ -114,17 +206,30 @@ fn convert_lexical_block(
} }
println!("Emitted return."); println!("Emitted return.");
} }
Stmt::IfElse(if_else) => {
convert_if_else(
context, module, builder, function, if_else, &scope_env,
)?;
}
} }
} }
Ok(()) Ok(())
} }
pub fn convert(context: &mut Context, program: Vec<Decl>) -> Result<Module> { pub fn convert(
let module = context.create_module("program"); file_name: String,
context: &Context,
program: Vec<Decl<Type>>,
) -> Result<Module> {
let module = context.create_module(&file_name);
let builder = context.create_builder(); let builder = context.create_builder();
for func in program.iter().filter_map(Decl::unwrap_func) { for func in program.iter().filter_map(|decl| match decl {
Decl::Func(v) => Some(v),
_ => None,
}) {
let return_ty = func.return_ty.into_llvm_basic_type(context); let return_ty = func.return_ty.into_llvm_basic_type(context);
let llvm_func_ty = fn_type_basic(return_ty, &[], false); let llvm_func_ty = fn_type_basic(return_ty, &[], false);
@ -134,7 +239,7 @@ pub fn convert(context: &mut Context, program: Vec<Decl>) -> Result<Module> {
builder.position_at_end(entry_block); builder.position_at_end(entry_block);
let env = Env::default(); let env = Env::default();
convert_lexical_block(context, &builder, env, &func.stmts)?; convert_stmts(&context, &module, &llvm_func, &builder, &env, &func.stmts)?;
} }
Ok(module) Ok(module)

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@ -1,39 +1,69 @@
pub mod llvm; pub mod llvm;
pub mod typed;
#[derive(Debug)] #[derive(Debug)]
pub enum Decl { pub enum Decl<T> {
Func(Func), Func(Func<T>),
} }
impl Decl { #[derive(Debug)]
pub fn unwrap_func(&self) -> Option<&Func> { pub struct Func<T> {
match self { pub name: String,
Decl::Func(func) => Some(func), pub return_ty: Type,
_ => None, pub stmts: Vec<Stmt<T>>,
} }
#[derive(Debug)]
pub enum Stmt<T> {
Let(String, Option<Type>, Expr<T>),
Return(Option<Expr<T>>),
IfElse(IfElse<T>),
}
#[derive(Debug)]
pub struct IfElse<T> {
pub cond: Expr<T>,
pub body: Vec<Stmt<T>>,
pub else_clause: Option<ElseClause<T>>,
}
#[derive(Debug)]
pub enum ElseClause<T> {
Body(Vec<Stmt<T>>),
If(Box<IfElse<T>>),
}
#[derive(Debug)]
pub struct Expr<T> {
pub kind: ExprKind<T>,
pub ty: T,
}
#[derive(Debug)]
pub enum ExprKind<T> {
Int(i64),
Var(String),
BinOp(Box<Expr<T>>, Op, Box<Expr<T>>),
}
#[derive(Copy, Clone, Debug)]
pub enum Op {
LessThan,
GreaterThan,
}
impl Op {
pub fn check_types(&self, left_ty: &Type, right_ty: &Type) -> bool {
// TODO: since only binops work on integers right now, just check that the two sides are both
// integers. this will have to change once && gets added.
matches!(left_ty, Type::Int) && matches!(right_ty, Type::Int)
} }
} }
#[derive(Debug)] #[derive(Clone, Debug, Hash, Eq, PartialEq)]
pub struct Func {
pub name: String,
pub return_ty: Type,
pub stmts: Vec<Stmt>,
}
#[derive(Debug)]
pub enum Stmt {
Let(String, Type, Expr),
Return(Option<Expr>),
}
#[derive(Debug)]
pub enum Expr {
Int(i64),
Var(String),
}
#[derive(Debug)]
pub enum Type { pub enum Type {
Int, Int,
Bool,
Func(Vec<Type>, Box<Type>),
} }

437
src/ast/typed.rs Normal file
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@ -0,0 +1,437 @@
use std::collections::{HashMap, HashSet};
use anyhow::Result;
use crate::ast::Expr;
use super::{Decl, ElseClause, ExprKind, Func, IfElse, Op, Stmt, Type};
#[derive(Clone, Debug, Hash, Eq, PartialEq)]
pub enum Type_ {
Var(usize),
Int,
Bool,
Func(Vec<Type_>, Box<Type_>),
}
impl Type_ {
fn from_type(ty: Type) -> Self {
match ty {
Type::Int => Type_::Int,
Type::Bool => Type_::Bool,
Type::Func(args, ret) => {
let args = args.into_iter().map(|arg| Type_::from_type(arg)).collect();
let ret = Type_::from_type(*ret);
Type_::Func(args, Box::new(ret))
}
}
}
fn convert(&self, assignments: &Assignments) -> Result<Type> {
Ok(match self {
Type_::Var(n) => match assignments.get(&n) {
Some(v) => v.convert(assignments)?,
None => bail!("Unsolved constraint variable {n}"),
},
Type_::Int => Type::Int,
Type_::Bool => Type::Bool,
Type_::Func(args, ret) => {
let args = args
.into_iter()
.map(|arg| arg.convert(assignments))
.collect::<Result<_>>()?;
let ret = ret.convert(assignments)?;
Type::Func(args, Box::new(ret))
}
})
}
}
impl Op {
fn constraints(
&self,
ctx: &mut AnnotationContext,
left: &Type_,
right: &Type_,
output: &Type_,
) {
match self {
Op::LessThan | Op::GreaterThan => {
ctx.constrain(left.clone(), Type_::Int);
ctx.constrain(right.clone(), Type_::Int);
ctx.constrain(output.clone(), Type_::Bool);
}
}
}
}
#[derive(Debug, Hash, Eq, PartialEq)]
struct Constraint(Type_, Type_);
#[derive(Default)]
struct Env {
parent: Option<Box<Env>>,
local_type_map: HashMap<String, Type_>,
}
impl Env {
pub fn lookup(&self, name: impl AsRef<str>) -> Option<&Type_> {
match self.local_type_map.get(name.as_ref()) {
Some(v) => Some(v),
None => match &self.parent {
Some(p) => p.lookup(name),
None => None,
},
}
}
}
struct AnnotationContext<'a> {
counter: usize,
constraints: &'a mut HashSet<Constraint>,
current_env: Option<Env>,
}
impl<'a> AnnotationContext<'a> {
pub fn type_var(&mut self) -> Type_ {
Type_::Var(self.gen_int())
}
pub fn gen_int(&mut self) -> usize {
let id = self.counter;
self.counter += 1;
id
}
pub fn constrain(&mut self, left: Type_, right: Type_) {
if left == right {
// No op, return now
return;
}
self.constraints.insert(Constraint(left, right));
}
pub fn lookup(&self, name: impl AsRef<str>) -> Option<&Type_> {
self.current_env.as_ref().unwrap().lookup(name)
}
pub fn define_var(&mut self, name: impl AsRef<str>, ty: Type_) {
self
.current_env
.as_mut()
.unwrap()
.local_type_map
.insert(name.as_ref().to_string(), ty);
}
pub fn push_scope(&mut self) {
self.current_env = Some(Env {
parent: Some(Box::new(self.current_env.take().unwrap())),
local_type_map: Default::default(),
});
}
pub fn pop_scope(&mut self) {
self.current_env =
Some(*self.current_env.take().unwrap().parent.take().unwrap());
}
}
fn annotate_stmts(
ctx: &mut AnnotationContext,
stmts: impl AsRef<[Stmt<()>]>,
) -> Vec<Stmt<Type_>> {
let stmts = stmts.as_ref();
let mut new_stmts = Vec::new();
ctx.push_scope();
for stmt in stmts.iter() {
match stmt {
Stmt::Return(ret_val) => {
let new_stmt =
Stmt::Return(ret_val.as_ref().map(|expr| annotate_expr(ctx, expr)));
new_stmts.push(new_stmt);
}
Stmt::Let(name, ty, body) => {
let new_stmt =
Stmt::Let(name.clone(), ty.clone(), annotate_expr(ctx, body));
let ty = match ty {
Some(v) => Type_::from_type(v.clone()),
None => ctx.type_var(),
};
ctx.define_var(name, ty);
new_stmts.push(new_stmt);
}
Stmt::IfElse(if_else) => {
let new_stmt = Stmt::IfElse(annotate_if_else(ctx, &if_else));
new_stmts.push(new_stmt);
}
}
}
ctx.pop_scope();
new_stmts
}
fn annotate_expr(ctx: &mut AnnotationContext, expr: &Expr<()>) -> Expr<Type_> {
match &expr.kind {
ExprKind::Int(n) => Expr {
kind: ExprKind::Int(*n),
ty: Type_::Int,
},
ExprKind::Var(name) => {
let ty = match ctx.lookup(name) {
Some(v) => v.clone(),
None => ctx.type_var(),
};
Expr {
kind: ExprKind::Var(name.clone()),
ty,
}
}
ExprKind::BinOp(left, op, right) => {
let left = annotate_expr(ctx, left);
let right = annotate_expr(ctx, right);
let output = ctx.type_var();
op.constraints(ctx, &left.ty, &right.ty, &output);
Expr {
kind: ExprKind::BinOp(Box::new(left), *op, Box::new(right)),
ty: output,
}
}
}
}
fn annotate_if_else(
ctx: &mut AnnotationContext,
if_else: &IfElse<()>,
) -> IfElse<Type_> {
let converted_cond = annotate_expr(ctx, &if_else.cond);
let converted_body = annotate_stmts(ctx, &if_else.body);
let else_clause = match &if_else.else_clause {
Some(ElseClause::If(if_else2)) => {
Some(ElseClause::If(Box::new(annotate_if_else(ctx, &if_else2))))
}
Some(ElseClause::Body(stmts)) => {
Some(ElseClause::Body(annotate_stmts(ctx, &stmts)))
}
None => None,
};
IfElse {
cond: converted_cond,
body: converted_body,
else_clause,
}
}
fn collect_info(func: &Func<()>) -> (Func<Type_>, HashSet<Constraint>) {
let mut constraints = HashSet::new();
let mut ctx = AnnotationContext {
counter: 0,
constraints: &mut constraints,
current_env: Some(Env::default()),
};
let new_stmts = annotate_stmts(&mut ctx, &func.stmts);
let func = Func {
name: func.name.clone(),
return_ty: func.return_ty.clone(),
stmts: new_stmts,
};
(func, constraints)
}
type Assignments = HashMap<usize, Type_>;
fn substitute_types(assignments: &Assignments, ty: &Type_) -> Type_ {
match ty {
Type_::Var(n) => match assignments.get(&n) {
Some(ty2) => ty2.clone(),
None => ty.clone(),
},
Type_::Func(args, ret) => {
let args = args
.into_iter()
.map(|arg| substitute_types(assignments, arg))
.collect();
let ret = substitute_types(assignments, &*ret);
Type_::Func(args, Box::new(ret))
}
Type_::Int | Type_::Bool => ty.clone(),
}
}
fn unify_constraints(constraints: &HashSet<Constraint>) -> Result<Assignments> {
let mut assignments = HashMap::new();
for Constraint(left, right) in constraints {
let left = substitute_types(&assignments, left);
let right = substitute_types(&assignments, right);
unify_single(&mut assignments, left, right)?;
}
Ok(assignments)
}
fn unify_single(
assignments: &mut Assignments,
left: Type_,
right: Type_,
) -> Result<()> {
match (left, right) {
(Type_::Int, Type_::Int) | (Type_::Bool, Type_::Bool) => {}
(Type_::Var(n), o) | (o, Type_::Var(n)) => {
assignments.insert(n, o);
}
(Type_::Func(left_args, left_ret), Type_::Func(right_args, right_ret)) => {
let mut new_constraints = HashSet::new();
for (left_arg, right_arg) in
left_args.into_iter().zip(right_args.into_iter())
{
new_constraints.insert(Constraint(left_arg, right_arg));
}
new_constraints.insert(Constraint(*left_ret, *right_ret));
assignments.extend(unify_constraints(&new_constraints)?);
}
(left, right) => bail!("Mismatching types {left:?} vs. {right:?}"),
};
Ok(())
}
fn substitute_in_expr_kind(
assignments: &Assignments,
expr_kind: ExprKind<Type_>,
) -> Result<ExprKind<Type>> {
Ok(match expr_kind {
ExprKind::Int(n) => ExprKind::Int(n),
ExprKind::Var(name) => ExprKind::Var(name),
ExprKind::BinOp(left, op, right) => {
let left = substitute_in_expr(assignments, *left)?;
let right = substitute_in_expr(assignments, *right)?;
ExprKind::BinOp(Box::new(left), op, Box::new(right))
}
})
}
fn substitute_in_expr(
assignments: &Assignments,
expr: Expr<Type_>,
) -> Result<Expr<Type>> {
Ok(Expr {
kind: substitute_in_expr_kind(assignments, expr.kind)?,
ty: expr.ty.convert(assignments)?,
})
}
fn substitute_in_if_else(
assignments: &Assignments,
if_else: IfElse<Type_>,
) -> Result<IfElse<Type>> {
let cond = substitute_in_expr(assignments, if_else.cond)?;
let body = substitute_in_stmts(assignments, if_else.body)?;
let else_clause = match if_else.else_clause {
Some(ElseClause::If(if_else2)) => Some(ElseClause::If(Box::new(
substitute_in_if_else(assignments, *if_else2)?,
))),
Some(ElseClause::Body(body)) => {
Some(ElseClause::Body(substitute_in_stmts(assignments, body)?))
}
None => None,
};
Ok(IfElse {
cond,
body,
else_clause,
})
}
fn substitute_in_stmts(
assignments: &Assignments,
stmts: Vec<Stmt<Type_>>,
) -> Result<Vec<Stmt<Type>>> {
stmts
.into_iter()
.map(|stmt| {
Ok(match stmt {
Stmt::Let(name, ty, body) => {
Stmt::Let(name, ty, substitute_in_expr(assignments, body)?)
}
Stmt::Return(ret_val) => Stmt::Return(match ret_val {
Some(v) => Some(substitute_in_expr(assignments, v)?),
None => None,
}),
Stmt::IfElse(if_else) => {
Stmt::IfElse(substitute_in_if_else(assignments, if_else)?)
}
})
})
.collect()
}
fn substitute_in_func(
assignments: &Assignments,
func: Func<Type_>,
) -> Result<Func<Type>> {
Ok(Func {
name: func.name,
return_ty: func.return_ty,
stmts: substitute_in_stmts(assignments, func.stmts)?,
})
}
pub fn convert(ast: Vec<Decl<()>>) -> Result<Vec<Decl<Type>>> {
// First pass, gather all of the type signatures in the top level
let mut top_level_signatures = HashMap::new();
for decl in ast.iter() {
match decl {
super::Decl::Func(func) => {
let name = func.name.clone();
let ty = Type::Func(Vec::new(), Box::new(func.return_ty.clone()));
top_level_signatures.insert(name, ty);
}
}
}
// Now, type-check each function separately
let mut new_decl = Vec::new();
for decl in ast.iter() {
match decl {
Decl::Func(func) => {
let (decorated_func, constraints) = collect_info(func);
println!("func: {:?}", decorated_func);
println!("constraints: {:?}", constraints);
let assignments = unify_constraints(&constraints)?;
println!("assignments: {:?}", assignments);
let typed_func = substitute_in_func(&assignments, decorated_func)?;
println!("typed: {:?}", typed_func);
new_decl.push(Decl::Func(typed_func));
}
}
}
Ok(new_decl)
}

View file

@ -6,6 +6,7 @@ extern crate anyhow;
lalrpop_mod!(parser); lalrpop_mod!(parser);
mod ast; mod ast;
mod utils;
use std::fs::{self, File}; use std::fs::{self, File};
use std::path::PathBuf; use std::path::PathBuf;
@ -32,14 +33,16 @@ struct Opt {
fn main() -> Result<()> { fn main() -> Result<()> {
let opts = Opt::parse(); let opts = Opt::parse();
let contents = fs::read_to_string(opts.path)?; let contents = fs::read_to_string(&opts.path)?;
let parser = ProgramParser::new(); let parser = ProgramParser::new();
let ast = parser.parse(&contents).unwrap(); let ast = parser.parse(&contents).unwrap();
println!("AST: {ast:?}");
let mut context = Context::create(); let typed_ast = ast::typed::convert(ast)?;
let module = ast::llvm::convert(&mut context, ast)?;
let context = Context::create();
let module =
ast::llvm::convert(opts.path.display().to_string(), &context, typed_ast)?;
{ {
let file = File::create(&opts.out_path)?; let file = File::create(&opts.out_path)?;

View file

@ -2,31 +2,57 @@ use crate::ast::*;
grammar; grammar;
pub Program: Vec<Decl> = Decl* => <>; pub Program: Vec<Decl<()>> = Decl* => <>;
Decl: Decl = { Decl: Decl<()> = {
Func => Decl::Func(<>), Func => Decl::Func(<>),
}; };
Func: Func = { Func: Func<()> = {
"fn" <name:Ident> "(" ")" "->" <return_ty:Type> "{" <stmts:Stmt*> "}" => "fn" <name:Ident> "(" ")" "->" <return_ty:Type> "{" <stmts:Stmt*> "}" =>
Func { name, return_ty, stmts }, Func { name, return_ty, stmts },
}; };
Stmt: Stmt = { Stmt: Stmt<()> = {
"let" <name:Ident> ":" <ty:Type> "=" <expr:Expr> ";" => "let" <name:Ident> <ty:ColonType?> "=" <expr:Expr> ";" =>
Stmt::Let(name, ty, expr), Stmt::Let(name, ty, expr),
"return" <expr:Expr?> ";" => Stmt::Return(expr), "return" <expr:Expr?> ";" => Stmt::Return(expr),
IfElse => Stmt::IfElse(<>),
}; };
Expr: Expr = { ColonType: Type = ":" <ty:Type> => ty;
Expr1 => <>,
IfElse: IfElse<()> =
"if" <cond:Expr> "{" <body:Stmt*> "}" <else_clause:Else?> =>
IfElse { cond, body, else_clause };
Else: ElseClause<()> = "else" <else_clause:Else_> => else_clause;
Else_: ElseClause<()> = {
IfElse => ElseClause::If(Box::new(<>)),
"{" <body:Stmt*> "}" => ElseClause::Body(body),
}; };
Expr1: Expr = { Expr: Expr<()> = {
r"[0-9]+" => Expr::Int(<>.parse::<i64>().unwrap()), #[precedence(level = "0")]
Ident => Expr::Var(<>),
"(" <expr:Expr> ")" => expr, "(" <expr:Expr> ")" => expr,
#[precedence(level = "0")]
r"[0-9]+" => Expr { kind: ExprKind::Int(<>.parse::<i64>().unwrap()), ty: () },
#[precedence(level = "0")]
Ident => Expr { kind: ExprKind::Var(<>), ty: () },
#[precedence(level = "13")]
#[assoc(side = "none")]
<left:Expr> <op:CompareOp> <right:Expr> => Expr {
kind: ExprKind::BinOp(Box::new(left), op, Box::new(right)),
ty: (),
},
};
CompareOp: Op = {
"<" => Op::LessThan,
">" => Op::GreaterThan,
}; };
Type: Type = { Type: Type = {

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// TODO: put layered environment here?