1 files changed, 161 insertions, 0 deletions
diff --git a/third_party/rust/nom/tests/arithmetic_ast.rs b/third_party/rust/nom/tests/arithmetic_ast.rs
new file mode 100644
index 0000000000..ca15110960
--- /dev/null
+++ b/third_party/rust/nom/tests/arithmetic_ast.rs
@@ -0,0 +1,161 @@
+use std::fmt;
+use std::fmt::{Debug, Display, Formatter};
+
+use std::str::FromStr;
+
+use nom::{
+  branch::alt,
+  bytes::complete::tag,
+  character::complete::{digit1 as digit, multispace0 as multispace},
+  combinator::{map, map_res},
+  multi::many0,
+  sequence::{delimited, preceded},
+  IResult,
+};
+
+pub enum Expr {
+  Value(i64),
+  Add(Box<Expr>, Box<Expr>),
+  Sub(Box<Expr>, Box<Expr>),
+  Mul(Box<Expr>, Box<Expr>),
+  Div(Box<Expr>, Box<Expr>),
+  Paren(Box<Expr>),
+}
+
+#[derive(Debug)]
+pub enum Oper {
+  Add,
+  Sub,
+  Mul,
+  Div,
+}
+
+impl Display for Expr {
+  fn fmt(&self, format: &mut Formatter<'_>) -> fmt::Result {
+    use self::Expr::*;
+    match *self {
+      Value(val) => write!(format, "{}", val),
+      Add(ref left, ref right) => write!(format, "{} + {}", left, right),
+      Sub(ref left, ref right) => write!(format, "{} - {}", left, right),
+      Mul(ref left, ref right) => write!(format, "{} * {}", left, right),
+      Div(ref left, ref right) => write!(format, "{} / {}", left, right),
+      Paren(ref expr) => write!(format, "({})", expr),
+    }
+  }
+}
+
+impl Debug for Expr {
+  fn fmt(&self, format: &mut Formatter<'_>) -> fmt::Result {
+    use self::Expr::*;
+    match *self {
+      Value(val) => write!(format, "{}", val),
+      Add(ref left, ref right) => write!(format, "({:?} + {:?})", left, right),
+      Sub(ref left, ref right) => write!(format, "({:?} - {:?})", left, right),
+      Mul(ref left, ref right) => write!(format, "({:?} * {:?})", left, right),
+      Div(ref left, ref right) => write!(format, "({:?} / {:?})", left, right),
+      Paren(ref expr) => write!(format, "[{:?}]", expr),
+    }
+  }
+}
+
+fn parens(i: &str) -> IResult<&str, Expr> {
+  delimited(
+    multispace,
+    delimited(tag("("), map(expr, |e| Expr::Paren(Box::new(e))), tag(")")),
+    multispace,
+  )(i)
+}
+
+fn factor(i: &str) -> IResult<&str, Expr> {
+  alt((
+    map(
+      map_res(delimited(multispace, digit, multispace), FromStr::from_str),
+      Expr::Value,
+    ),
+    parens,
+  ))(i)
+}
+
+fn fold_exprs(initial: Expr, remainder: Vec<(Oper, Expr)>) -> Expr {
+  remainder.into_iter().fold(initial, |acc, pair| {
+    let (oper, expr) = pair;
+    match oper {
+      Oper::Add => Expr::Add(Box::new(acc), Box::new(expr)),
+      Oper::Sub => Expr::Sub(Box::new(acc), Box::new(expr)),
+      Oper::Mul => Expr::Mul(Box::new(acc), Box::new(expr)),
+      Oper::Div => Expr::Div(Box::new(acc), Box::new(expr)),
+    }
+  })
+}
+
+fn term(i: &str) -> IResult<&str, Expr> {
+  let (i, initial) = factor(i)?;
+  let (i, remainder) = many0(alt((
+    |i| {
+      let (i, mul) = preceded(tag("*"), factor)(i)?;
+      Ok((i, (Oper::Mul, mul)))
+    },
+    |i| {
+      let (i, div) = preceded(tag("/"), factor)(i)?;
+      Ok((i, (Oper::Div, div)))
+    },
+  )))(i)?;
+
+  Ok((i, fold_exprs(initial, remainder)))
+}
+
+fn expr(i: &str) -> IResult<&str, Expr> {
+  let (i, initial) = term(i)?;
+  let (i, remainder) = many0(alt((
+    |i| {
+      let (i, add) = preceded(tag("+"), term)(i)?;
+      Ok((i, (Oper::Add, add)))
+    },
+    |i| {
+      let (i, sub) = preceded(tag("-"), term)(i)?;
+      Ok((i, (Oper::Sub, sub)))
+    },
+  )))(i)?;
+
+  Ok((i, fold_exprs(initial, remainder)))
+}
+
+#[test]
+fn factor_test() {
+  assert_eq!(
+    factor("  3  ").map(|(i, x)| (i, format!("{:?}", x))),
+    Ok(("", String::from("3")))
+  );
+}
+
+#[test]
+fn term_test() {
+  assert_eq!(
+    term(" 3 *  5   ").map(|(i, x)| (i, format!("{:?}", x))),
+    Ok(("", String::from("(3 * 5)")))
+  );
+}
+
+#[test]
+fn expr_test() {
+  assert_eq!(
+    expr(" 1 + 2 *  3 ").map(|(i, x)| (i, format!("{:?}", x))),
+    Ok(("", String::from("(1 + (2 * 3))")))
+  );
+  assert_eq!(
+    expr(" 1 + 2 *  3 / 4 - 5 ").map(|(i, x)| (i, format!("{:?}", x))),
+    Ok(("", String::from("((1 + ((2 * 3) / 4)) - 5)")))
+  );
+  assert_eq!(
+    expr(" 72 / 2 / 3 ").map(|(i, x)| (i, format!("{:?}", x))),
+    Ok(("", String::from("((72 / 2) / 3)")))
+  );
+}
+
+#[test]
+fn parens_test() {
+  assert_eq!(
+    expr(" ( 1 + 2 ) *  3 ").map(|(i, x)| (i, format!("{:?}", x))),
+    Ok(("", String::from("([(1 + 2)] * 3)")))
+  );
+}