typing: cleanup imports and fix unit in return

src/typing/mod.rs

@@ -1,15 +1,10 @@
+mod error;
+
+use crate::ast::*;
+use crate::typing::error::{TypeAndSpan, TypeError, TypeErrorKind};
 use std::collections::HashMap;
 use std::fmt::Display;
 
-use BinaryExpression;
-use ReturnStatement;
-
-use crate::ast::ModulePath;
-use crate::ast::*;
-
-mod error;
-use crate::typing::error::{TypeAndSpan, TypeError, TypeErrorKind};
-
 #[cfg(test)]
 mod tests;
 
@@ -178,7 +173,7 @@ impl TypeCheck for FunctionDefinition {
             );
         }
 
-        Ok(self.return_type.clone().unwrap())
+        Ok(self.return_type.clone().unwrap_or(Type::Unit))
     }
 }