From bcf48d0ecbb1ffd4688ce7fde9aaf01f695c6706 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Wed, 20 Feb 2019 01:33:45 -0800
Subject: [PATCH] First tests for typechecking

---
 schala-lang/language/src/lib.rs          |  4 +-
 schala-lang/language/src/typechecking.rs | 62 +++++++++++++++++++++---
 2 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/schala-lang/language/src/lib.rs b/schala-lang/language/src/lib.rs
index d28cc22..aaa26dc 100644
--- a/schala-lang/language/src/lib.rs
+++ b/schala-lang/language/src/lib.rs
@@ -169,8 +169,8 @@ fn typechecking(input: ast::AST, handle: &mut Schala, comp: Option<&mut Unfinish
 
   comp.map(|comp| {
     let artifact = TraceArtifact::new("type", match result {
-      Ok(typestring) => typestring,
-      Err(err) => format!("Type error: {}", err)
+      Ok(ty) => ty.to_string(),
+      Err(err) => format!("Type error: {}", err.msg)
     });
     comp.add_artifact(artifact);
   });
diff --git a/schala-lang/language/src/typechecking.rs b/schala-lang/language/src/typechecking.rs
index a0a9666..e31db7a 100644
--- a/schala-lang/language/src/typechecking.rs
+++ b/schala-lang/language/src/typechecking.rs
@@ -6,7 +6,7 @@ use std::rc::Rc;
 
 use crate::ast::*;
 use crate::util::ScopeStack;
-use crate::builtin::PrefixOp;
+use crate::builtin::{PrefixOp, BinOp};
 
 pub type TypeName = Rc<String>;
 
@@ -19,7 +19,7 @@ pub struct TypeContext<'a> {
 type InferResult<T> = Result<T, TypeError>;
 
 #[derive(Debug, Clone)]
-struct TypeError { msg: String }
+pub struct TypeError { pub msg: String }
 
 impl TypeError {
   fn new<A>(msg: &str) -> InferResult<A> { //TODO make these kinds of error-producing functions CoW-ready
@@ -27,7 +27,7 @@ impl TypeError {
   }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum Type {
   Const(TypeConst),
   Arrow(Box<Type>, Box<Type>),
@@ -57,7 +57,7 @@ macro_rules! ty {
 
 //TODO find a better way to capture the to/from string logic
 impl Type {
-  fn to_string(&self) -> String {
+  pub fn to_string(&self) -> String {
     use self::Type::*;
     use self::TypeConst::*;
     match self {
@@ -193,12 +193,12 @@ impl<'a> TypeContext<'a> {
 
   }
 
-  pub fn typecheck(&mut self, ast: &AST) -> Result<String, String> {
+  pub fn typecheck(&mut self, ast: &AST) -> Result<Type, TypeError> {
     let mut returned_type = Type::Const(TypeConst::Unit);
     for statement in ast.0.iter() {
-      returned_type = self.statement(statement.node()).map_err(|err| { err.msg })?
+      returned_type = self.statement(statement.node())?;
     }
-    Ok(returned_type.to_string())
+    Ok(returned_type)
   }
 
   fn statement(&mut self, statement: &Statement) -> InferResult<Type> {
@@ -239,8 +239,10 @@ impl<'a> TypeContext<'a> {
       FloatLiteral(_) => ty!(Float),
       StringLiteral(_) => ty!(StringT),
       PrefixExp(op, expr) => self.prefix(op, expr.node())?,
+      BinExp(op, lhs, rhs) => self.binexp(op, lhs.node(), rhs.node())?,
       IfExpression { discriminator, body } => self.if_expr(discriminator, body)?,
       Value(val) => self.handle_value(val)?,
+      Lambda { params, type_anno, body } => self.lambda(params, type_anno, body)?,
       _ => ty!(Unit),
     })
   }
@@ -255,10 +257,20 @@ impl<'a> TypeContext<'a> {
     self.handle_apply(f, x)
   }
 
-  fn handle_apply(&mut self, f: Type, x: Type) -> InferResult<Type> {
+  fn binexp(&mut self, op: &BinOp, lhs: &Expression, rhs: &Expression) -> InferResult<Type> {
     Ok(ty!(Unit))
   }
 
+  fn handle_apply(&mut self, tf: Type, tx: Type) -> InferResult<Type> {
+    Ok(match tf {
+      Type::Arrow(ref t1, ref t2) => {
+        let _ = self.unify(*t1.clone(), tx)?;
+        *t2.clone()
+      },
+      _ => return TypeError::new(&format!("Not a function"))
+    })
+  }
+
   fn if_expr(&mut self, discriminator: &Discriminator, body: &IfExpressionBody) -> InferResult<Type> {
     use self::Discriminator::*; use self::IfExpressionBody::*;
     match (discriminator, body) {
@@ -279,6 +291,10 @@ impl<'a> TypeContext<'a> {
     self.unify(t2, t3)
   }
 
+  fn lambda(&mut self, params: &Vec<FormalParam>, type_anno: &Option<TypeIdentifier>, body: &Block) -> InferResult<Type> {
+    Ok(ty!(Unit))
+  }
+
   fn block(&mut self, block: &Block) -> InferResult<Type> {
     let mut output = ty!(Unit);
     for s in block.iter() {
@@ -303,3 +319,33 @@ impl<'a> TypeContext<'a> {
     })
   }
 }
+
+#[cfg(test)]
+mod typechecking_tests {
+  use super::*;
+  use crate::ast::AST;
+
+  fn parse(input: &str) -> AST {
+    let tokens = crate::tokenizing::tokenize(input);
+    let mut parser = crate::parsing::Parser::new(tokens);
+    parser.parse().unwrap()
+  }
+
+  macro_rules! assert_type_in_fresh_context {
+    ($string:expr, $type:expr) => {
+      let mut tc = TypeContext::new();
+      let ref ast = parse($string);
+      let ty = tc.typecheck(ast).unwrap();
+      assert_eq!(ty, $type)
+    }
+  }
+
+  #[test]
+  fn basic_test() {
+    assert_type_in_fresh_context!("1", ty!(Nat));
+    assert_type_in_fresh_context!(r#""drugs""#, ty!(StringT));
+    assert_type_in_fresh_context!("true", ty!(Bool));
+    assert_type_in_fresh_context!("-1", ty!(Int));
+  }
+
+}