Add the start of a hindley-milner typechecker

The beginning of a parse-don't-validate-based hindley-milner
typechecker, which returns on success an IR where every AST node
trivially knows its own type, and using those types to determine LLVM
types in codegen.

3 files changed, 27 insertions, 4 deletions

diff --git a/src/parser/expr.rs b/src/parser/expr.rs
index 2fda3e93fae9..73c873b5b304 100644
--- a/src/parser/expr.rs
+++ b/src/parser/expr.rs
@@ -156,7 +156,14 @@ where
 
 named!(int(&str) -> Literal, map!(flat_map!(digit1, parse_to!(u64)), Literal::Int));
 
-named!(literal(&str) -> Expr, map!(alt!(int), Expr::Literal));
+named!(bool_(&str) -> Literal, alt!(
+    tag!("true") => { |_| Literal::Bool(true) } |
+    tag!("false") => { |_| Literal::Bool(false) }
+));
+
+named!(literal(&str) -> Literal, alt!(int | bool_));
+
+named!(literal_expr(&str) -> Expr, map!(literal, Expr::Literal));
 
 named!(binding(&str) -> Binding, do_parse!(
     multispace0
@@ -262,7 +269,7 @@ named!(fun_expr(&str) -> Expr, do_parse!(
 
 named!(arg(&str) -> Expr, alt!(
     ident_expr |
-    literal |
+    literal_expr |
     paren_expr
 ));
 
@@ -280,7 +287,7 @@ named!(simple_expr_unascripted(&str) -> Expr, alt!(
     let_ |
     if_ |
     fun_expr |
-    literal |
+    literal_expr |
     ident_expr
 ));
 
@@ -400,6 +407,18 @@ pub(crate) mod tests {
     }
 
     #[test]
+    fn bools() {
+        assert_eq!(
+            test_parse!(expr, "true"),
+            Expr::Literal(Literal::Bool(true))
+        );
+        assert_eq!(
+            test_parse!(expr, "false"),
+            Expr::Literal(Literal::Bool(false))
+        );
+    }
+
+    #[test]
     fn let_complex() {
         let res = test_parse!(expr, "let x = 1; y = x * 7 in (x + y) * 4");
         assert_eq!(
diff --git a/src/parser/macros.rs b/src/parser/macros.rs
index 60db5133dc0f..406e5c0e699e 100644
--- a/src/parser/macros.rs
+++ b/src/parser/macros.rs
@@ -1,3 +1,4 @@
+#[cfg(test)]
 #[macro_use]
 macro_rules! test_parse {
     ($parser: ident, $src: expr) => {{
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index af7dff6ff213..0251d02df464 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -14,7 +14,10 @@ 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")
+    matches!(
+        s,
+        "if" | "then" | "else" | "let" | "in" | "fn" | "int" | "float" | "bool" | "true" | "false"
+    )
 }
 
 pub(crate) fn ident<'a, E>(i: &'a str) -> nom::IResult<&'a str, Ident, E>