3 files changed, 59 insertions, 13 deletions
diff --git a/src/semantic/environment.rs b/src/semantic/environment.rs
index fab16b3..7876ad4 100644
--- a/src/semantic/environment.rs
+++ b/src/semantic/environment.rs
@@ -15,6 +15,10 @@ impl<'a, T: 'a, U: 'a> Environment<'a, T, U>
         }
     }
 
+    pub fn set_parent(&mut self, parent: &'a Environment<'a, T, U>) {
+        self.parent = Some(parent);
+    }
+
     pub fn add_binding(&mut self, key: T, value: U) {
         self.bindings.insert(key, value);
     }
diff --git a/src/semantic/translate.rs b/src/semantic/translate.rs
index d3ebd2c..9da6411 100644
--- a/src/semantic/translate.rs
+++ b/src/semantic/translate.rs
@@ -9,6 +9,7 @@ pub enum TypeError {
         expected: Ty,
         actual: Ty,
     },
+    UnboundName,
 }
 
 type TypeEnvironment<'a> = environment::Environment<'a, String, Ty>;
@@ -19,23 +20,59 @@ pub fn translate(program: &ast::Program) -> Result {
     trans_exp(&mut env, &*program.0)
 }
 
+macro_rules! err {
+    ($exp: expr, $err: expr) => {
+        Err(WithLocation::new($err, $exp.start, $exp.end))
+    }
+}
+
 fn trans_exp<'a>(venv: &mut TypeEnvironment<'a>, exp: &WithLocation<ast::Expression>) -> Result {
     use ast::Expression::*;
 
     match &exp.value {
         &Let(ref decls, ref body) => {
-            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+            let mut new_env = TypeEnvironment::new(None);
+            for decl in decls.iter() {
+                let decl_ty = trans_exp(venv, &*decl.value.value)?;
+                if let Some(_) = decl.value.type_ {
+                    return err!(decl, TypeError::Unimplemented);
+                }
+                else {
+                    new_env.add_binding(decl.value.name.value.clone(), decl_ty);
+                }
+            }
+            new_env.set_parent(venv);
+            trans_exp(&mut new_env, &*body)
         },
         &UnaryOp(ref op, ref operand) => {
-            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+            use ast::UnaryOp::*;
+            let operand_ty = trans_exp(venv, operand)?;
+            match op {
+                &Neg | &Pos => {
+                    match operand_ty {
+                        Ty::Int => {
+                            Ok(Ty::Int)
+                        }
+                        other => {
+                            err!(operand, TypeError::Mismatch {
+                                expected: Ty::Int,
+                                actual: other,
+                            })
+                        }
+                    }
+                }
+                &Not => {
+                    err!(exp, TypeError::Unimplemented)
+                }
+            }
         },
         &BinOp(ref op, ref left, ref right) => {
             use ast::BinOp::*;
+            let left_ty = trans_exp(venv, left)?;
+            let right_ty = trans_exp(venv, right)?;
             match op {
                 &Add => {
-                    let left = trans_exp(venv, left)?;
-                    let right = trans_exp(venv, right)?;
-                    match (left, right) {
+                    match (left_ty, right_ty) {
                         (Ty::Int, Ty::Int) => {
                             Ok(Ty::Int)
                         }
@@ -43,31 +80,36 @@ fn trans_exp<'a>(venv: &mut TypeEnvironment<'a>, exp: &WithLocation<ast::Express
                             Ok(Ty::String)
                         }
                         (Ty::Int, other) => {
-                            Err(WithLocation::new(TypeError::Mismatch {
+                            err!(right, TypeError::Mismatch {
                                 expected: Ty::Int,
                                 actual: other,
-                            }, exp.start, exp.end))
+                            })
                         }
                         (Ty::String, other) => {
-                            Err(WithLocation::new(TypeError::Mismatch {
+                            err!(right, TypeError::Mismatch {
                                 expected: Ty::String,
                                 actual: other,
-                            }, exp.start, exp.end))
+                            })
                         }
                         _ => {
-                            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+                            err!(exp, TypeError::Unimplemented)
                         }
                     }
                 }
                 _ => {
-                    Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+                    err!(exp, TypeError::Unimplemented)
                 }
             }
         },
         &Number(_) => Ok(Ty::Int),
         &String(_) => Ok(Ty::String),
         &Name(ref name) => {
-            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+            if let Some(ty) = venv.lookup(name) {
+                Ok(*ty)
+            }
+            else {
+                err!(exp, TypeError::UnboundName)
+            }
         },
         &Nil => {
             Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
diff --git a/src/semantic/types.rs b/src/semantic/types.rs
index 2d76387..3e31b04 100644
--- a/src/semantic/types.rs
+++ b/src/semantic/types.rs
@@ -1,4 +1,4 @@
-#[derive(Debug)]
+#[derive(Clone,Copy,Debug)]
 pub enum Ty {
     Int,
     String,