refactor type assertion solving

dynamic-check/src/dynamic_check.rs

@@ -16,6 +16,7 @@
 
 use crate::{DynamicCheckError, FrameError, ScopeError, TypeAssertionError, VariableTableError};
 use leo_static_check::{
+    flatten_array_type,
     Attribute,
     CircuitFunctionType,
     CircuitType,
@@ -1253,21 +1254,42 @@ impl Frame {
 
             println!("assertion: {:?}", type_assertion);
 
+            // Collect `TypeVariablePairs` from the `TypeAssertion`.
+            let pairs = type_assertion.pairs()?;
+
+            // If no pairs are found, attempt to evaluate the `TypeAssertion`.
+            if pairs.is_empty() {
+                // Evaluate the `TypeAssertion`.
+                type_assertion.evaluate()?
+            } else {
+                // Iterate over each `TypeVariable` -> `Type` pair.
+                for pair in pairs.get_pairs() {
+                    // Substitute the `TypeVariable` for it's paired `Type` in all `TypeAssertion`s.
+                    for original in &mut unsolved {
+                        original.substitute(&pair.0, &pair.1)
+                    }
+
+                    for original in &mut unsolved_membership {
+                        original.substitute(&pair.0, &pair.1)
+                    }
+                }
+            }
+
             // Solve the `TypeAssertion`.
             //
             // If the `TypeAssertion` has a solution, then continue the loop.
             // If the `TypeAssertion` returns a `TypeVariablePair`, then substitute the `TypeVariable`
             // for it's paired `Type` in all `TypeAssertion`s.
-            if let Some(pair) = type_assertion.solve()? {
+            // if let Some(pair) = type_assertion.solve()? {
-                // Substitute the `TypeVariable` for it's paired `Type` in all `TypeAssertion`s.
+            //     // Substitute the `TypeVariable` for it's paired `Type` in all `TypeAssertion`s.
-                for original in &mut unsolved {
+            //     for original in &mut unsolved {
-                    original.substitute(&pair.0, &pair.1)
+            //         original.substitute(&pair.0, &pair.1)
-                }
+            //     }
-
+            //
-                for original in &mut unsolved_membership {
+            //     for original in &mut unsolved_membership {
-                    original.substitute(&pair.0, &pair.1)
+            //         original.substitute(&pair.0, &pair.1)
-                }
+            //     }
-            };
+            // };
         }
 
         // Solve all type membership assertions.
@@ -1276,7 +1298,7 @@ impl Frame {
             let type_assertion = unsolved_membership.pop().unwrap();
 
             // Solve the membership assertion.
-            type_assertion.solve()?;
+            type_assertion.evaluate()?;
         }
 
         // for type_assertion in unsolved.pop() {
@@ -1420,9 +1442,6 @@ impl VariableTable {
     }
 }
 
-/// A type variable -> type pair.
-pub struct TypeVariablePair(TypeVariable, Type);
-
 /// A predicate that evaluates equality between two `Types`s.
 #[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
 pub enum TypeAssertion {
@@ -1445,8 +1464,19 @@ impl TypeAssertion {
         Self::Membership(TypeMembership::new(given, set, span))
     }
 
+    ///
+    /// Returns one or more `TypeVariablePairs` generated by the given `TypeAssertion`.
+    ///
+    pub fn pairs(&self) -> Result<TypeVariablePairs, TypeAssertionError> {
+        match self {
+            TypeAssertion::Equality(equality) => equality.pairs(),
+            TypeAssertion::Membership(_) => unimplemented!("Cannot generate pairs from type membership"),
+        }
+    }
+
     ///
     /// Substitutes the given type for self if self is equal to the type variable.
+    ///
     pub fn substitute(&mut self, variable: &TypeVariable, type_: &Type) {
         match self {
             TypeAssertion::Equality(equality) => equality.substitute(variable, type_),
@@ -1455,19 +1485,12 @@ impl TypeAssertion {
     }
 
     ///
-    /// Returns `None` if the `TypeAssertion` is solvable.
+    /// Checks if the `TypeAssertion` is satisfied.
     ///
-    /// If the `TypeAssertion` is not solvable, throw a `TypeAssertionError`.
+    pub fn evaluate(&self) -> Result<(), TypeAssertionError> {
-    /// If the `TypeAssertion` contains a `TypeVariable`, then return `Some(TypeVariable, Type)`.
-    ///
-    pub fn solve(&self) -> Result<Option<TypeVariablePair>, TypeAssertionError> {
         match self {
-            TypeAssertion::Equality(equality) => equality.solve(),
+            TypeAssertion::Equality(equality) => equality.evaluate(),
-            TypeAssertion::Membership(membership) => {
+            TypeAssertion::Membership(membership) => membership.evaluate(),
-                membership.solve()?;
-
-                Ok(None)
-            }
         }
     }
 }
@@ -1502,7 +1525,7 @@ impl TypeMembership {
     ///
     /// Returns true if the given type is equal to a member of the set.
     ///
-    pub fn solve(&self) -> Result<(), TypeAssertionError> {
+    pub fn evaluate(&self) -> Result<(), TypeAssertionError> {
         if self.set.contains(&self.given) {
             Ok(())
         } else {
@@ -1555,22 +1578,120 @@ impl TypeEquality {
         self.right.substitute(variable, type_);
     }
 
+    ///
+    /// Checks if the `self.left` == `self.right`.
+    ///
+    pub fn evaluate(&self) -> Result<(), TypeAssertionError> {
+        if self.left.eq(&self.right) {
+            Ok(())
+        } else {
+            Err(TypeAssertionError::equality_failed(&self.left, &self.right, &self.span))
+        }
+    }
+
     ///
     /// Returns the (type variable, type) pair from this assertion.
     ///
-    pub fn solve(&self) -> Result<Option<TypeVariablePair>, TypeAssertionError> {
+    pub fn pairs(&self) -> Result<TypeVariablePairs, TypeAssertionError> {
-        Ok(match (&self.left, &self.right) {
+        TypeVariablePairs::new(&self.left, &self.right, &self.span)
-            (Type::TypeVariable(variable), type_) => Some(TypeVariablePair(variable.clone(), type_.clone())),
+    }
-            (type_, Type::TypeVariable(variable)) => Some(TypeVariablePair(variable.clone(), type_.clone())),
+}
-            (type1, type2) => {
+
-                // Compare types.
+/// A type variable -> type pair.
-                if type1.eq(type2) {
+pub struct TypeVariablePair(TypeVariable, Type);
-                    // Return None if the two types are equal (the equality is satisfied).
+
-                    None
+/// A vector of `TypeVariablePair`s.
-                } else {
+pub struct TypeVariablePairs(Vec<TypeVariablePair>);
-                    return Err(TypeAssertionError::equality_failed(type1, type2, &self.span));
+
-                }
+impl Default for TypeVariablePairs {
-            }
+    fn default() -> Self {
-        })
+        Self(Vec::new())
+    }
+}
+
+impl TypeVariablePairs {
+    ///
+    /// Returns a new `TypeVariablePairs` struct from the given left and right types.
+    ///
+    pub fn new(left: &Type, right: &Type, span: &Span) -> Result<Self, TypeAssertionError> {
+        let mut pairs = Self::default();
+
+        // Push all `TypeVariablePair`s.
+        pairs.push_pairs(left, right, span)?;
+
+        Ok(pairs)
+    }
+
+    ///
+    /// Returns true if the self vector has no pairs.
+    ///
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    ///
+    /// Returns the self vector of pairs.
+    ///
+    pub fn get_pairs(&self) -> &Vec<TypeVariablePair> {
+        &self.0
+    }
+
+    ///
+    /// Pushes a new `TypeVariablePair` struct to self.
+    ///
+    pub fn push(&mut self, variable: &TypeVariable, type_: &Type) {
+        // Create a new type variable -> type pair.
+        let pair = TypeVariablePair(variable.clone(), type_.clone());
+
+        // Push the pair to the self vector.
+        self.0.push(pair);
+    }
+
+    ///
+    /// Checks if the given left or right type contains a `TypeVariable`.
+    /// If a `TypeVariable` is found, create a new `TypeVariablePair` between the given left
+    /// and right type.
+    ///
+    pub fn push_pairs(&mut self, left: &Type, right: &Type, span: &Span) -> Result<(), TypeAssertionError> {
+        match (left, right) {
+            (Type::TypeVariable(variable), type_) => Ok(self.push(variable, type_)),
+            (type_, Type::TypeVariable(variable)) => Ok(self.push(variable, type_)),
+            (Type::Array(type1, dimensions1), Type::Array(type2, dimensions2)) => {
+                self.push_pairs_array(type1, dimensions1, type2, dimensions2, span)
+            }
+            (_, _) => Ok(()), // No `TypeVariable` found so we do not push any pairs.
+        }
+    }
+
+    ///
+    /// Checks if the given left or right array type contains a `TypeVariable`.
+    /// If a `TypeVariable` is found, create a new `TypeVariablePair` between the given left
+    /// and right type.
+    ///
+    fn push_pairs_array(
+        &mut self,
+        left_type: &Type,
+        left_dimensions: &Vec<usize>,
+        right_type: &Type,
+        right_dimensions: &Vec<usize>,
+        span: &Span,
+    ) -> Result<(), TypeAssertionError> {
+        // Flatten the array types to get the element types.
+        let (left_type_flat, left_dimensions_flat) = flatten_array_type(left_type, left_dimensions.to_owned());
+        let (right_type_flat, right_dimensions_flat) = flatten_array_type(right_type, right_dimensions.to_owned());
+
+        // If the dimensions do not match, then throw an error.
+        if left_dimensions_flat.ne(&right_dimensions_flat) {
+            return Err(TypeAssertionError::array_dimensions(
+                left_dimensions_flat,
+                right_dimensions_flat,
+                span,
+            ));
+        }
+
+        // Compare the array element types.
+        self.push_pairs(left_type_flat, right_type_flat, span);
+
+        Ok(())
     }
 }

dynamic-check/src/errors/type_assertion.rs

@@ -63,4 +63,16 @@ impl TypeAssertionError {
 
         Self::new_from_span(message, span.to_owned())
     }
+
+    ///
+    /// Mismatched array type dimensions.
+    ///
+    pub fn array_dimensions(dimensions1: Vec<usize>, dimensions2: Vec<usize>, span: &Span) -> Self {
+        let message = format!(
+            "Expected array with dimensions `{:?}`, found array with dimensions `{:?}`.",
+            dimensions1, dimensions2
+        );
+
+        Self::new_from_span(message, span.to_owned())
+    }
 }

static-check/src/types/type_.rs

@@ -311,7 +311,7 @@ impl Eq for Type {}
 ///
 /// Will flatten an array type `[[[u8; 1]; 2]; 3]` into `[u8; (3, 2, 1)]`.
 ///
-fn flatten_array_type(type_: &Type, mut dimensions: Vec<usize>) -> (&Type, Vec<usize>) {
+pub fn flatten_array_type(type_: &Type, mut dimensions: Vec<usize>) -> (&Type, Vec<usize>) {
     if let Type::Array(element_type, element_dimensions) = type_ {
         dimensions.append(&mut element_dimensions.to_owned());
         flatten_array_type(element_type, dimensions)