merge(glittershark/achilles): Subtree import at 'b93268085a' r/2279

Imported from https://github.com/glittershark/achilles/

git-subtree-dir: users/glittershark/achilles
git-subtree-mainline: 4d193f239525954631ba9d789ca3aea9a2f4e14d
git-subtree-split: b93268085aab14c80a400c299da5d04d2781098e
Change-Id: I64a583b454bbe03e20358ad7808939a4cbc212ba

1 files changed, 197 insertions, 0 deletions

diff --git a/users/glittershark/achilles/src/parser/mod.rs b/users/glittershark/achilles/src/parser/mod.rs
new file mode 100644
index 000000000000..dd7874aff853
--- /dev/null
+++ b/users/glittershark/achilles/src/parser/mod.rs
@@ -0,0 +1,197 @@
+use nom::character::complete::{multispace0, multispace1};
+use nom::error::{ErrorKind, ParseError};
+use nom::{alt, char, complete, do_parse, many0, named, separated_list0, tag, terminated};
+
+#[macro_use]
+mod macros;
+mod expr;
+mod type_;
+
+use crate::ast::{Arg, Decl, Fun, Ident};
+pub use expr::expr;
+pub use type_::type_;
+
+pub type Error = nom::Err<nom::error::Error<String>>;
+
+pub(crate) fn is_reserved(s: &str) -> bool {
+    matches!(
+        s,
+        "if" | "then"
+            | "else"
+            | "let"
+            | "in"
+            | "fn"
+            | "int"
+            | "float"
+            | "bool"
+            | "true"
+            | "false"
+            | "cstring"
+    )
+}
+
+pub(crate) fn ident<'a, E>(i: &'a str) -> nom::IResult<&'a str, Ident, E>
+where
+    E: ParseError<&'a str>,
+{
+    let mut chars = i.chars();
+    if let Some(f) = chars.next() {
+        if f.is_alphabetic() || f == '_' {
+            let mut idx = 1;
+            for c in chars {
+                if !(c.is_alphanumeric() || c == '_') {
+                    break;
+                }
+                idx += 1;
+            }
+            let id = &i[..idx];
+            if is_reserved(id) {
+                Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Satisfy)))
+            } else {
+                Ok((&i[idx..], Ident::from_str_unchecked(id)))
+            }
+        } else {
+            Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Satisfy)))
+        }
+    } else {
+        Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Eof)))
+    }
+}
+
+named!(ascripted_arg(&str) -> Arg, do_parse!(
+    complete!(char!('(')) >>
+        multispace0 >>
+        ident: ident >>
+        multispace0 >>
+        complete!(char!(':')) >>
+        multispace0 >>
+        type_: type_ >>
+        multispace0 >>
+        complete!(char!(')')) >>
+        (Arg {
+            ident,
+            type_: Some(type_)
+        })
+));
+
+named!(arg(&str) -> Arg, alt!(
+    ident => { |ident| Arg {ident, type_: None}} |
+    ascripted_arg
+));
+
+named!(fun_decl(&str) -> Decl, do_parse!(
+    complete!(tag!("fn"))
+        >> multispace0
+        >> name: ident
+        >> multispace1
+        >> args: separated_list0!(multispace1, arg)
+        >> multispace0
+        >> char!('=')
+        >> multispace0
+        >> body: expr
+        >> (Decl::Fun {
+            name,
+            body: Fun {
+                args,
+                body
+            }
+        })
+));
+
+named!(ascription_decl(&str) -> Decl, do_parse!(
+    name: ident
+        >> multispace0
+        >> complete!(char!(':'))
+        >> multispace0
+        >> type_: type_
+        >> (Decl::Ascription {
+            name,
+            type_
+        })
+));
+
+named!(pub decl(&str) -> Decl, alt!(
+    ascription_decl |
+    fun_decl
+));
+
+named!(pub toplevel(&str) -> Vec<Decl>, terminated!(many0!(decl), multispace0));
+
+#[cfg(test)]
+mod tests {
+    use std::convert::TryInto;
+
+    use crate::ast::{BinaryOperator, Expr, FunctionType, Literal, Type};
+
+    use super::*;
+    use expr::tests::ident_expr;
+
+    #[test]
+    fn fn_decl() {
+        let res = test_parse!(decl, "fn id x = x");
+        assert_eq!(
+            res,
+            Decl::Fun {
+                name: "id".try_into().unwrap(),
+                body: Fun {
+                    args: vec!["x".try_into().unwrap()],
+                    body: *ident_expr("x"),
+                }
+            }
+        )
+    }
+
+    #[test]
+    fn ascripted_fn_args() {
+        test_parse!(ascripted_arg, "(x : int)");
+        let res = test_parse!(decl, "fn plus1 (x : int) = x + 1");
+        assert_eq!(
+            res,
+            Decl::Fun {
+                name: "plus1".try_into().unwrap(),
+                body: Fun {
+                    args: vec![Arg {
+                        ident: "x".try_into().unwrap(),
+                        type_: Some(Type::Int),
+                    }],
+                    body: Expr::BinaryOp {
+                        lhs: ident_expr("x"),
+                        op: BinaryOperator::Add,
+                        rhs: Box::new(Expr::Literal(Literal::Int(1))),
+                    }
+                }
+            }
+        );
+    }
+
+    #[test]
+    fn multiple_decls() {
+        let res = test_parse!(
+            toplevel,
+            "fn id x = x
+             fn plus x y = x + y
+             fn main = plus (id 2) 7"
+        );
+        assert_eq!(res.len(), 3);
+        let res = test_parse!(
+            toplevel,
+            "fn id x = x\nfn plus x y = x + y\nfn main = plus (id 2) 7\n"
+        );
+        assert_eq!(res.len(), 3);
+    }
+
+    #[test]
+    fn top_level_ascription() {
+        let res = test_parse!(toplevel, "id : fn a -> a");
+        assert_eq!(
+            res,
+            vec![Decl::Ascription {
+                name: "id".try_into().unwrap(),
+                type_: Type::Function(FunctionType {
+                    args: vec![Type::Var("a".try_into().unwrap())],
+                    ret: Box::new(Type::Var("a".try_into().unwrap()))
+                })
+            }]
+        )
+    }
+}