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, 45 insertions, 2 deletions

diff --git a/src/commands/check.rs b/src/commands/check.rs
new file mode 100644
index 000000000000..40de288a282c
--- /dev/null
+++ b/src/commands/check.rs
@@ -0,0 +1,39 @@
+use clap::Clap;
+use std::path::PathBuf;
+
+use crate::ast::Type;
+use crate::{parser, tc, Result};
+
+/// Typecheck a file or expression
+#[derive(Clap)]
+pub struct Check {
+    /// File to check
+    path: Option<PathBuf>,
+
+    /// Expression to check
+    #[clap(long, short = 'e')]
+    expr: Option<String>,
+}
+
+fn run_expr(expr: String) -> Result<Type> {
+    let (_, parsed) = parser::expr(&expr)?;
+    let hir_expr = tc::typecheck_expr(parsed)?;
+    Ok(hir_expr.type_().clone())
+}
+
+fn run_path(path: PathBuf) -> Result<Type> {
+    todo!()
+}
+
+impl Check {
+    pub fn run(self) -> Result<()> {
+        let type_ = match (self.path, self.expr) {
+            (None, None) => Err("Must specify either a file or expression to check".into()),
+            (Some(_), Some(_)) => Err("Cannot specify both a file and expression to check".into()),
+            (None, Some(expr)) => run_expr(expr),
+            (Some(path), None) => run_path(path),
+        }?;
+        println!("type: {}", type_);
+        Ok(())
+    }
+}
diff --git a/src/commands/eval.rs b/src/commands/eval.rs
index 112bee64625b..61a712c08a8e 100644
--- a/src/commands/eval.rs
+++ b/src/commands/eval.rs
@@ -3,6 +3,7 @@ use clap::Clap;
 use crate::codegen;
 use crate::interpreter;
 use crate::parser;
+use crate::tc;
 use crate::Result;
 
 /// Evaluate an expression and print its result
@@ -19,10 +20,11 @@ pub struct Eval {
 impl Eval {
     pub fn run(self) -> Result<()> {
         let (_, parsed) = parser::expr(&self.expr)?;
+        let hir = tc::typecheck_expr(parsed)?;
         let result = if self.jit {
-            codegen::jit_eval::<i64>(&parsed)?.into()
+            codegen::jit_eval::<i64>(&hir)?.into()
         } else {
-            interpreter::eval(&parsed)?
+            interpreter::eval(&hir)?
         };
         println!("{}", result);
         Ok(())
diff --git a/src/commands/mod.rs b/src/commands/mod.rs
index 9c0038dabfb1..fd0a822708c2 100644
--- a/src/commands/mod.rs
+++ b/src/commands/mod.rs
@@ -1,5 +1,7 @@
+pub mod check;
 pub mod compile;
 pub mod eval;
 
+pub use check::Check;
 pub use compile::Compile;
 pub use eval::Eval;