refactor(users/glittershark): Rename to grfn r/2485

Rename my //users directory and all places that refer to glittershark to
grfn, including nix references and documentation.

This may require some extra attention inside of gerrit's database after
it lands to allow me to actually push things.

Change-Id: I4728b7ec2c60024392c1c1fa6e0d4a59b3e266fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2933
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: glittershark <grfn@gws.fyi>

3 files changed, 404 insertions, 0 deletions

diff --git a/users/grfn/achilles/src/interpreter/error.rs b/users/grfn/achilles/src/interpreter/error.rs
new file mode 100644
index 000000000000..268d6f479a1e
--- /dev/null
+++ b/users/grfn/achilles/src/interpreter/error.rs
@@ -0,0 +1,19 @@
+use std::result;
+
+use thiserror::Error;
+
+use crate::ast::{Ident, Type};
+
+#[derive(Debug, PartialEq, Eq, Error)]
+pub enum Error {
+    #[error("Undefined variable {0}")]
+    UndefinedVariable(Ident<'static>),
+
+    #[error("Unexpected type {actual}, expected type {expected}")]
+    InvalidType {
+        actual: Type<'static>,
+        expected: Type<'static>,
+    },
+}
+
+pub type Result<T> = result::Result<T, Error>;
diff --git a/users/grfn/achilles/src/interpreter/mod.rs b/users/grfn/achilles/src/interpreter/mod.rs
new file mode 100644
index 000000000000..a8ba2dd3acdc
--- /dev/null
+++ b/users/grfn/achilles/src/interpreter/mod.rs
@@ -0,0 +1,182 @@
+mod error;
+mod value;
+
+pub use self::error::{Error, Result};
+pub use self::value::{Function, Value};
+use crate::ast::hir::{Binding, Expr};
+use crate::ast::{BinaryOperator, FunctionType, Ident, Literal, Type, UnaryOperator};
+use crate::common::env::Env;
+
+#[derive(Debug, Default)]
+pub struct Interpreter<'a> {
+    env: Env<&'a Ident<'a>, Value<'a>>,
+}
+
+impl<'a> Interpreter<'a> {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn resolve(&self, var: &'a Ident<'a>) -> Result<Value<'a>> {
+        self.env
+            .resolve(var)
+            .cloned()
+            .ok_or_else(|| Error::UndefinedVariable(var.to_owned()))
+    }
+
+    pub fn eval(&mut self, expr: &'a Expr<'a, Type>) -> Result<Value<'a>> {
+        let res = match expr {
+            Expr::Ident(id, _) => self.resolve(id),
+            Expr::Literal(Literal::Int(i), _) => Ok((*i).into()),
+            Expr::Literal(Literal::Bool(b), _) => Ok((*b).into()),
+            Expr::Literal(Literal::String(s), _) => Ok(s.clone().into()),
+            Expr::Literal(Literal::Unit, _) => unreachable!(),
+            Expr::UnaryOp { op, rhs, .. } => {
+                let rhs = self.eval(rhs)?;
+                match op {
+                    UnaryOperator::Neg => -rhs,
+                    _ => unimplemented!(),
+                }
+            }
+            Expr::BinaryOp { lhs, op, rhs, .. } => {
+                let lhs = self.eval(lhs)?;
+                let rhs = self.eval(rhs)?;
+                match op {
+                    BinaryOperator::Add => lhs + rhs,
+                    BinaryOperator::Sub => lhs - rhs,
+                    BinaryOperator::Mul => lhs * rhs,
+                    BinaryOperator::Div => lhs / rhs,
+                    BinaryOperator::Pow => todo!(),
+                    BinaryOperator::Equ => Ok(lhs.eq(&rhs).into()),
+                    BinaryOperator::Neq => todo!(),
+                }
+            }
+            Expr::Let { bindings, body, .. } => {
+                self.env.push();
+                for Binding { ident, body, .. } in bindings {
+                    let val = self.eval(body)?;
+                    self.env.set(ident, val);
+                }
+                let res = self.eval(body)?;
+                self.env.pop();
+                Ok(res)
+            }
+            Expr::If {
+                condition,
+                then,
+                else_,
+                ..
+            } => {
+                let condition = self.eval(condition)?;
+                if *(condition.as_type::<bool>()?) {
+                    self.eval(then)
+                } else {
+                    self.eval(else_)
+                }
+            }
+            Expr::Call { ref fun, args, .. } => {
+                let fun = self.eval(fun)?;
+                let expected_type = FunctionType {
+                    args: args.iter().map(|_| Type::Int).collect(),
+                    ret: Box::new(Type::Int),
+                };
+
+                let Function {
+                    args: function_args,
+                    body,
+                    ..
+                } = fun.as_function(expected_type)?;
+                let arg_values = function_args.iter().zip(
+                    args.iter()
+                        .map(|v| self.eval(v))
+                        .collect::<Result<Vec<_>>>()?,
+                );
+                let mut interpreter = Interpreter::new();
+                for (arg_name, arg_value) in arg_values {
+                    interpreter.env.set(arg_name, arg_value);
+                }
+                Ok(Value::from(*interpreter.eval(body)?.as_type::<i64>()?))
+            }
+            Expr::Fun {
+                type_args: _,
+                args,
+                body,
+                type_,
+            } => {
+                let type_ = match type_ {
+                    Type::Function(ft) => ft.clone(),
+                    _ => unreachable!("Function expression without function type"),
+                };
+
+                Ok(Value::from(value::Function {
+                    // TODO
+                    type_,
+                    args: args.iter().map(|(arg, _)| arg.to_owned()).collect(),
+                    body: (**body).to_owned(),
+                }))
+            }
+        }?;
+        debug_assert_eq!(&res.type_(), expr.type_());
+        Ok(res)
+    }
+}
+
+pub fn eval<'a>(expr: &'a Expr<'a, Type>) -> Result<Value<'a>> {
+    let mut interpreter = Interpreter::new();
+    interpreter.eval(expr)
+}
+
+#[cfg(test)]
+mod tests {
+    use std::convert::TryFrom;
+
+    use super::value::{TypeOf, Val};
+    use super::*;
+    use BinaryOperator::*;
+
+    fn int_lit(i: u64) -> Box<Expr<'static, Type<'static>>> {
+        Box::new(Expr::Literal(Literal::Int(i), Type::Int))
+    }
+
+    fn do_eval<T>(src: &str) -> T
+    where
+        for<'a> &'a T: TryFrom<&'a Val<'a>>,
+        T: Clone + TypeOf,
+    {
+        let expr = crate::parser::expr(src).unwrap().1;
+        let hir = crate::tc::typecheck_expr(expr).unwrap();
+        let res = eval(&hir).unwrap();
+        res.as_type::<T>().unwrap().clone()
+    }
+
+    #[test]
+    fn simple_addition() {
+        let expr = Expr::BinaryOp {
+            lhs: int_lit(1),
+            op: Mul,
+            rhs: int_lit(2),
+            type_: Type::Int,
+        };
+        let res = eval(&expr).unwrap();
+        assert_eq!(*res.as_type::<i64>().unwrap(), 2);
+    }
+
+    #[test]
+    fn variable_shadowing() {
+        let res = do_eval::<i64>("let x = 1 in (let x = 2 in x) + x");
+        assert_eq!(res, 3);
+    }
+
+    #[test]
+    fn conditional_with_equals() {
+        let res = do_eval::<i64>("let x = 1 in if x == 1 then 2 else 4");
+        assert_eq!(res, 2);
+    }
+
+    #[test]
+    #[ignore]
+    fn function_call() {
+        let res = do_eval::<i64>("let id = fn x = x in id 1");
+        assert_eq!(res, 1);
+    }
+}
diff --git a/users/grfn/achilles/src/interpreter/value.rs b/users/grfn/achilles/src/interpreter/value.rs
new file mode 100644
index 000000000000..55ba42f9de58
--- /dev/null
+++ b/users/grfn/achilles/src/interpreter/value.rs
@@ -0,0 +1,203 @@
+use std::borrow::Cow;
+use std::convert::TryFrom;
+use std::fmt::{self, Display};
+use std::ops::{Add, Div, Mul, Neg, Sub};
+use std::rc::Rc;
+use std::result;
+
+use derive_more::{Deref, From, TryInto};
+
+use super::{Error, Result};
+use crate::ast::hir::Expr;
+use crate::ast::{FunctionType, Ident, Type};
+
+#[derive(Debug, Clone)]
+pub struct Function<'a> {
+    pub type_: FunctionType<'a>,
+    pub args: Vec<Ident<'a>>,
+    pub body: Expr<'a, Type<'a>>,
+}
+
+#[derive(From, TryInto)]
+#[try_into(owned, ref)]
+pub enum Val<'a> {
+    Int(i64),
+    Float(f64),
+    Bool(bool),
+    String(Cow<'a, str>),
+    Function(Function<'a>),
+}
+
+impl<'a> TryFrom<Val<'a>> for String {
+    type Error = ();
+
+    fn try_from(value: Val<'a>) -> result::Result<Self, Self::Error> {
+        match value {
+            Val::String(s) => Ok(s.into_owned()),
+            _ => Err(()),
+        }
+    }
+}
+
+impl<'a> fmt::Debug for Val<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Val::Int(x) => f.debug_tuple("Int").field(x).finish(),
+            Val::Float(x) => f.debug_tuple("Float").field(x).finish(),
+            Val::Bool(x) => f.debug_tuple("Bool").field(x).finish(),
+            Val::String(s) => f.debug_tuple("String").field(s).finish(),
+            Val::Function(Function { type_, .. }) => {
+                f.debug_struct("Function").field("type_", type_).finish()
+            }
+        }
+    }
+}
+
+impl<'a> PartialEq for Val<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Val::Int(x), Val::Int(y)) => x == y,
+            (Val::Float(x), Val::Float(y)) => x == y,
+            (Val::Bool(x), Val::Bool(y)) => x == y,
+            (Val::Function(_), Val::Function(_)) => false,
+            (_, _) => false,
+        }
+    }
+}
+
+impl<'a> From<u64> for Val<'a> {
+    fn from(i: u64) -> Self {
+        Self::from(i as i64)
+    }
+}
+
+impl<'a> Display for Val<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Val::Int(x) => x.fmt(f),
+            Val::Float(x) => x.fmt(f),
+            Val::Bool(x) => x.fmt(f),
+            Val::String(s) => write!(f, "{:?}", s),
+            Val::Function(Function { type_, .. }) => write!(f, "<{}>", type_),
+        }
+    }
+}
+
+impl<'a> Val<'a> {
+    pub fn type_(&self) -> Type {
+        match self {
+            Val::Int(_) => Type::Int,
+            Val::Float(_) => Type::Float,
+            Val::Bool(_) => Type::Bool,
+            Val::String(_) => Type::CString,
+            Val::Function(Function { type_, .. }) => Type::Function(type_.clone()),
+        }
+    }
+
+    pub fn as_type<'b, T>(&'b self) -> Result<&'b T>
+    where
+        T: TypeOf + 'b + Clone,
+        &'b T: TryFrom<&'b Self>,
+    {
+        <&T>::try_from(self).map_err(|_| Error::InvalidType {
+            actual: self.type_().to_owned(),
+            expected: <T as TypeOf>::type_of(),
+        })
+    }
+
+    pub fn as_function<'b>(&'b self, function_type: FunctionType) -> Result<&'b Function<'a>> {
+        match self {
+            Val::Function(f) if f.type_ == function_type => Ok(&f),
+            _ => Err(Error::InvalidType {
+                actual: self.type_().to_owned(),
+                expected: Type::Function(function_type.to_owned()),
+            }),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Clone, Deref)]
+pub struct Value<'a>(Rc<Val<'a>>);
+
+impl<'a> Display for Value<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<'a, T> From<T> for Value<'a>
+where
+    Val<'a>: From<T>,
+{
+    fn from(x: T) -> Self {
+        Self(Rc::new(x.into()))
+    }
+}
+
+impl<'a> Neg for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn neg(self) -> Self::Output {
+        Ok((-self.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Add for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<i64>()? + rhs.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Sub for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<i64>()? - rhs.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Mul for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn mul(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<i64>()? * rhs.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Div for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn div(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<f64>()? / rhs.as_type::<f64>()?).into())
+    }
+}
+
+pub trait TypeOf {
+    fn type_of() -> Type<'static>;
+}
+
+impl TypeOf for i64 {
+    fn type_of() -> Type<'static> {
+        Type::Int
+    }
+}
+
+impl TypeOf for bool {
+    fn type_of() -> Type<'static> {
+        Type::Bool
+    }
+}
+
+impl TypeOf for f64 {
+    fn type_of() -> Type<'static> {
+        Type::Float
+    }
+}
+
+impl TypeOf for String {
+    fn type_of() -> Type<'static> {
+        Type::CString
+    }
+}