Implement basic type checking

src/abstract_tree/assignment.rs

@@ -28,8 +28,14 @@ impl<'src> AbstractTree for Assignment<'src> {
         todo!()
     }
 
-    fn validate(&self, _context: &Context) -> Result<(), ValidationError> {
-        todo!()
+    fn validate(&self, context: &Context) -> Result<(), ValidationError> {
+        if let Some(expected) = &self.r#type {
+            let statement_type = self.statement.expected_type(context)?;
+
+            expected.check(&statement_type)?;
+        }
+
+        Ok(())
     }
 
     fn run(self, context: &Context) -> Result<Value, RuntimeError> {
@@ -43,7 +49,10 @@ impl<'src> AbstractTree for Assignment<'src> {
 
 #[cfg(test)]
 mod tests {
-    use crate::abstract_tree::{Expression, ValueNode};
+    use crate::{
+        abstract_tree::{Expression, ValueNode},
+        error::TypeCheckError,
+    };
 
     use super::*;
 
@@ -64,4 +73,22 @@ mod tests {
             Ok(Some(Value::integer(42)))
         )
     }
+
+    #[test]
+    fn type_check() {
+        let validation = Assignment::new(
+            Identifier::new("foobar"),
+            Some(Type::Boolean),
+            Statement::Expression(Expression::Value(ValueNode::Integer(42))),
+        )
+        .validate(&Context::new());
+
+        assert_eq!(
+            validation,
+            Err(ValidationError::TypeCheck(TypeCheckError {
+                actual: Type::Integer,
+                expected: Type::Boolean
+            }))
+        )
+    }
 }

src/abstract_tree/type.rs

@@ -1,9 +1,15 @@
-use crate::abstract_tree::Identifier;
+use crate::{
+    abstract_tree::Identifier,
+    context::Context,
+    error::{RuntimeError, TypeCheckError, ValidationError},
+    Value,
+};
 
 use super::AbstractTree;
 
 #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
 pub enum Type {
+    Any,
     Boolean,
     Custom(Identifier),
     Float,
@@ -12,29 +18,181 @@ pub enum Type {
     ListOf(Box<Type>),
     ListExact(Vec<Type>),
     Map,
+    None,
     Range,
     String,
 }
 
+impl Type {
+    pub fn check(&self, other: &Type) -> Result<(), TypeCheckError> {
+        match (self, other) {
+            (Type::Any, _)
+            | (_, Type::Any)
+            | (Type::Boolean, Type::Boolean)
+            | (Type::Float, Type::Float)
+            | (Type::Integer, Type::Integer)
+            | (Type::List, Type::List)
+            | (Type::List, Type::ListOf(_))
+            | (Type::List, Type::ListExact(_))
+            | (Type::ListOf(_), Type::List)
+            | (Type::ListExact(_), Type::List)
+            | (Type::Map, Type::Map)
+            | (Type::None, Type::None)
+            | (Type::Range, Type::Range)
+            | (Type::String, Type::String) => Ok(()),
+            (Type::Custom(left), Type::Custom(right)) => {
+                if left == right {
+                    Ok(())
+                } else {
+                    Err(TypeCheckError {
+                        actual: other.clone(),
+                        expected: self.clone(),
+                    })
+                }
+            }
+            (Type::ListOf(left), Type::ListOf(right)) => {
+                if let Ok(()) = left.check(right) {
+                    Ok(())
+                } else {
+                    Err(TypeCheckError {
+                        actual: left.as_ref().clone(),
+                        expected: right.as_ref().clone(),
+                    })
+                }
+            }
+            (Type::ListOf(list_of), Type::ListExact(list_exact)) => {
+                for r#type in list_exact {
+                    list_of.check(r#type)?;
+                }
+
+                Ok(())
+            }
+            (Type::ListExact(list_exact), Type::ListOf(list_of)) => {
+                for r#type in list_exact {
+                    r#type.check(&list_of)?;
+                }
+
+                Ok(())
+            }
+            (Type::ListExact(left), Type::ListExact(right)) => {
+                for (left, right) in left.iter().zip(right.iter()) {
+                    left.check(right)?;
+                }
+
+                Ok(())
+            }
+            _ => Err(TypeCheckError {
+                actual: other.clone(),
+                expected: self.clone(),
+            }),
+        }
+    }
+}
+
 impl AbstractTree for Type {
-    fn expected_type(
-        &self,
-        context: &crate::context::Context,
-    ) -> Result<Type, crate::error::ValidationError> {
-        todo!()
+    fn expected_type(&self, _: &Context) -> Result<Type, ValidationError> {
+        Ok(Type::None)
     }
 
-    fn validate(
-        &self,
-        context: &crate::context::Context,
-    ) -> Result<(), crate::error::ValidationError> {
-        todo!()
+    fn validate(&self, _: &Context) -> Result<(), ValidationError> {
+        Ok(())
     }
 
-    fn run(
-        self,
-        context: &crate::context::Context,
-    ) -> Result<crate::Value, crate::error::RuntimeError> {
-        todo!()
+    fn run(self, _: &Context) -> Result<Value, RuntimeError> {
+        Ok(Value::none())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn check_same_types() {
+        assert_eq!(Type::Any.check(&Type::Any), Ok(()));
+        assert_eq!(Type::Boolean.check(&Type::Boolean), Ok(()));
+        assert_eq!(
+            Type::Custom(Identifier::new("foo")).check(&Type::Custom(Identifier::new("foo"))),
+            Ok(())
+        );
+        assert_eq!(Type::Float.check(&Type::Float), Ok(()));
+        assert_eq!(Type::Integer.check(&Type::Integer), Ok(()));
+        assert_eq!(Type::List.check(&Type::List), Ok(()));
+        assert_eq!(
+            Type::ListOf(Box::new(Type::Integer)).check(&Type::ListOf(Box::new(Type::Integer))),
+            Ok(())
+        );
+
+        assert_eq!(
+            Type::ListExact(vec![Type::Float]).check(&Type::ListExact(vec![Type::Float])),
+            Ok(())
+        );
+        assert_eq!(Type::Map.check(&Type::Map), Ok(()));
+        assert_eq!(Type::None.check(&Type::None), Ok(()));
+        assert_eq!(Type::Range.check(&Type::Range), Ok(()));
+        assert_eq!(Type::String.check(&Type::String), Ok(()));
+    }
+
+    #[test]
+    fn errors() {
+        let foo = Type::Custom(Identifier::new("foo"));
+        let bar = Type::Custom(Identifier::new("bar"));
+
+        assert_eq!(
+            foo.check(&bar),
+            Err(TypeCheckError {
+                actual: bar.clone(),
+                expected: foo.clone()
+            })
+        );
+        assert_eq!(
+            bar.check(&foo),
+            Err(TypeCheckError {
+                actual: foo.clone(),
+                expected: bar.clone()
+            })
+        );
+
+        let types = [
+            Type::Any,
+            Type::Boolean,
+            Type::Float,
+            Type::Integer,
+            Type::List,
+            Type::ListOf(Box::new(Type::Boolean)),
+            Type::ListExact(vec![Type::Integer]),
+            Type::Map,
+            Type::None,
+            Type::Range,
+            Type::String,
+        ];
+
+        for (left, right) in types.iter().zip(types.iter()) {
+            if left == right {
+                continue;
+            }
+
+            assert_eq!(
+                left.check(right),
+                Err(TypeCheckError {
+                    actual: right.clone(),
+                    expected: left.clone()
+                })
+            );
+        }
+    }
+
+    #[test]
+    fn check_list_types() {
+        let list = Type::List;
+        let list_exact = Type::ListExact(vec![Type::Integer, Type::Integer]);
+        let list_of = Type::ListOf(Box::new(Type::Integer));
+
+        assert_eq!(list.check(&list_exact), Ok(()));
+        assert_eq!(list.check(&list_of), Ok(()));
+        assert_eq!(list_exact.check(&list), Ok(()));
+        assert_eq!(list_exact.check(&list_of), Ok(()));
+        assert_eq!(list_of.check(&list), Ok(()));
+        assert_eq!(list_of.check(&list_exact), Ok(()));
     }
 }

src/error.rs

@@ -2,7 +2,7 @@ use std::sync::PoisonError;
 
 use chumsky::prelude::Rich;
 
-use crate::lexer::Token;
+use crate::{abstract_tree::Type, lexer::Token};
 
 #[derive(Debug, PartialEq)]
 pub enum Error<'src> {
@@ -49,8 +49,9 @@ impl From<ValidationError> for RuntimeError {
 
 #[derive(Debug, PartialEq)]
 pub enum ValidationError {
-    RwLockPoison(RwLockPoisonError),
     ExpectedBoolean,
+    RwLockPoison(RwLockPoisonError),
+    TypeCheck(TypeCheckError),
 }
 
 impl From<RwLockPoisonError> for ValidationError {
@@ -59,6 +60,12 @@ impl From<RwLockPoisonError> for ValidationError {
     }
 }
 
+impl From<TypeCheckError> for ValidationError {
+    fn from(error: TypeCheckError) -> Self {
+        ValidationError::TypeCheck(error)
+    }
+}
+
 #[derive(Debug, PartialEq)]
 pub struct RwLockPoisonError;
 
@@ -67,3 +74,9 @@ impl<T> From<PoisonError<T>> for RwLockPoisonError {
         RwLockPoisonError
     }
 }
+
+#[derive(Debug, PartialEq)]
+pub struct TypeCheckError {
+    pub actual: Type,
+    pub expected: Type,
+}