trying to modify visitor pattern to better fit type checking

compiler/ast/src/passes/visitor.rs

@@ -30,35 +30,37 @@ impl Default for VisitResult {
 }
 
 pub trait ExpressionVisitor<'a> {
-    fn visit_expression(&mut self, _input: &'a Expression) -> VisitResult {
+    type Output;
+
+    fn visit_expression(&mut self, _input: &'a Expression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_identifier(&mut self, _input: &'a Identifier) -> VisitResult {
+    fn visit_identifier(&mut self, _input: &'a Identifier) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_value(&mut self, _input: &'a ValueExpression) -> VisitResult {
+    fn visit_value(&mut self, _input: &'a ValueExpression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_binary(&mut self, _input: &'a BinaryExpression) -> VisitResult {
+    fn visit_binary(&mut self, _input: &'a BinaryExpression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_unary(&mut self, _input: &'a UnaryExpression) -> VisitResult {
+    fn visit_unary(&mut self, _input: &'a UnaryExpression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_ternary(&mut self, _input: &'a TernaryExpression) -> VisitResult {
+    fn visit_ternary(&mut self, _input: &'a TernaryExpression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_call(&mut self, _input: &'a CallExpression) -> VisitResult {
+    fn visit_call(&mut self, _input: &'a CallExpression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 
-    fn visit_err(&mut self, _input: &'a ErrExpression) -> VisitResult {
+    fn visit_err(&mut self, _input: &'a ErrExpression) -> (VisitResult, Option<Self::Output>) {
         Default::default()
     }
 }

compiler/ast/src/passes/visitor_director.rs

@@ -18,72 +18,87 @@
 //! It implements default methods for each node to be made
 //! given the type of node its visiting.
 
-use std::marker::PhantomData;
-
 use crate::*;
 
-pub struct VisitorDirector<'a, V: ExpressionVisitor<'a>> {
-    visitor: V,
-    lifetime: PhantomData<&'a ()>,
+pub trait VisitorDirector<'a> {
+    type Visitor: ExpressionVisitor<'a> + ProgramVisitor<'a> + StatementVisitor<'a>;
+
+    fn visitor(self) -> Self::Visitor;
+
+    fn visitor_ref(&mut self) -> &mut Self::Visitor;
 }
 
-impl<'a, V: ExpressionVisitor<'a>> VisitorDirector<'a, V> {
-    pub fn new(visitor: V) -> Self {
-        Self {
-            visitor,
-            lifetime: PhantomData,
-        }
-    }
+pub trait ExpressionVisitorDirector<'a>: VisitorDirector<'a> {
+    type Output;
 
-    pub fn visitor(self) -> V {
-        self.visitor
-    }
-
-    pub fn visit_expression(&mut self, input: &'a Expression) {
-        if let VisitResult::VisitChildren = self.visitor.visit_expression(input) {
+    fn visit_expression(&mut self, input: &'a Expression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_expression(input).0 {
             match input {
-                Expression::Identifier(_) => {}
-                Expression::Value(_) => {}
+                Expression::Identifier(expr) => self.visit_identifier(expr),
+                Expression::Value(expr) => self.visit_value(expr),
                 Expression::Binary(expr) => self.visit_binary(expr),
                 Expression::Unary(expr) => self.visit_unary(expr),
                 Expression::Ternary(expr) => self.visit_ternary(expr),
                 Expression::Call(expr) => self.visit_call(expr),
-                Expression::Err(_) => {}
-            }
-        }
+                Expression::Err(expr) => self.visit_err(expr),
+            };
         }
 
-    pub fn visit_binary(&mut self, input: &'a BinaryExpression) {
-        if let VisitResult::VisitChildren = self.visitor.visit_binary(input) {
+        None
+    }
+
+    fn visit_identifier(&mut self, input: &'a Identifier) -> Option<Self::Output> {
+        self.visitor_ref().visit_identifier(input);
+        None
+    }
+
+    fn visit_value(&mut self, input: &'a ValueExpression) -> Option<Self::Output> {
+        self.visitor_ref().visit_value(input);
+        None
+    }
+
+    fn visit_binary(&mut self, input: &'a BinaryExpression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_binary(input).0 {
             self.visit_expression(&input.left);
             self.visit_expression(&input.right);
         }
+        None
     }
 
-    pub fn visit_unary(&mut self, input: &'a UnaryExpression) {
-        if let VisitResult::VisitChildren = self.visitor.visit_unary(input) {
+    fn visit_unary(&mut self, input: &'a UnaryExpression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_unary(input).0 {
             self.visit_expression(&input.inner);
         }
+        None
     }
 
-    pub fn visit_ternary(&mut self, input: &'a TernaryExpression) {
-        if let VisitResult::VisitChildren = self.visitor.visit_ternary(input) {
+    fn visit_ternary(&mut self, input: &'a TernaryExpression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_ternary(input).0 {
             self.visit_expression(&input.condition);
             self.visit_expression(&input.if_true);
             self.visit_expression(&input.if_false);
         }
+        None
     }
 
-    pub fn visit_call(&mut self, input: &'a CallExpression) {
-        if let VisitResult::VisitChildren = self.visitor.visit_call(input) {
-            input.arguments.iter().for_each(|expr| self.visit_expression(expr));
+    fn visit_call(&mut self, input: &'a CallExpression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_call(input).0 {
+            input.arguments.iter().for_each(|expr| {
+                self.visit_expression(expr);
+            });
         }
+        None
+    }
+
+    fn visit_err(&mut self, input: &'a ErrExpression) -> Option<Self::Output> {
+        self.visitor_ref().visit_err(input);
+        None
     }
 }
 
-impl<'a, V: ExpressionVisitor<'a> + StatementVisitor<'a>> VisitorDirector<'a, V> {
-    pub fn visit_statement(&mut self, input: &'a Statement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_statement(input) {
+pub trait StatementVisitorDirector<'a>: VisitorDirector<'a> + ExpressionVisitorDirector<'a> {
+    fn visit_statement(&mut self, input: &'a Statement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_statement(input) {
             match input {
                 Statement::Return(stmt) => self.visit_return(stmt),
                 Statement::Definition(stmt) => self.visit_definition(stmt),
@@ -96,26 +111,26 @@ impl<'a, V: ExpressionVisitor<'a> + StatementVisitor<'a>> VisitorDirector<'a, V>
         }
     }
 
-    pub fn visit_return(&mut self, input: &'a ReturnStatement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_return(input) {
-            self.visit_expression(&input.expression);
+    fn visit_return(&mut self, input: &'a ReturnStatement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_return(input) {
+            self.visitor_ref().visit_expression(&input.expression);
         }
     }
 
-    pub fn visit_definition(&mut self, input: &'a DefinitionStatement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_definition(input) {
+    fn visit_definition(&mut self, input: &'a DefinitionStatement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_definition(input) {
             self.visit_expression(&input.value);
         }
     }
 
-    pub fn visit_assign(&mut self, input: &'a AssignStatement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_assign(input) {
+    fn visit_assign(&mut self, input: &'a AssignStatement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_assign(input) {
             self.visit_expression(&input.value);
         }
     }
 
-    pub fn visit_conditional(&mut self, input: &'a ConditionalStatement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_conditional(input) {
+    fn visit_conditional(&mut self, input: &'a ConditionalStatement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_conditional(input) {
             self.visit_expression(&input.condition);
             self.visit_block(&input.block);
             if let Some(stmt) = input.next.as_ref() {
@@ -124,35 +139,38 @@ impl<'a, V: ExpressionVisitor<'a> + StatementVisitor<'a>> VisitorDirector<'a, V>
         }
     }
 
-    pub fn visit_iteration(&mut self, input: &'a IterationStatement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_iteration(input) {
+    fn visit_iteration(&mut self, input: &'a IterationStatement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_iteration(input) {
             self.visit_expression(&input.start);
             self.visit_expression(&input.stop);
             self.visit_block(&input.block);
         }
     }
 
-    pub fn visit_console(&mut self, input: &'a ConsoleStatement) {
-        if let VisitResult::VisitChildren = self.visitor.visit_console(input) {
+    fn visit_console(&mut self, input: &'a ConsoleStatement) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_console(input) {
             match &input.function {
                 ConsoleFunction::Assert(expr) => self.visit_expression(expr),
                 ConsoleFunction::Error(fmt) | ConsoleFunction::Log(fmt) => {
-                    fmt.parameters.iter().for_each(|expr| self.visit_expression(expr));
-                }
+                    fmt.parameters.iter().for_each(|expr| {
+                        self.visit_expression(expr);
+                    });
+                    None
                 }
+            };
         }
     }
 
-    pub fn visit_block(&mut self, input: &'a Block) {
-        if let VisitResult::VisitChildren = self.visitor.visit_block(input) {
+    fn visit_block(&mut self, input: &'a Block) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_block(input) {
             input.statements.iter().for_each(|stmt| self.visit_statement(stmt));
         }
     }
 }
 
-impl<'a, V: ExpressionVisitor<'a> + ProgramVisitor<'a> + StatementVisitor<'a>> VisitorDirector<'a, V> {
-    pub fn visit_program(&mut self, input: &'a Program) {
-        if let VisitResult::VisitChildren = self.visitor.visit_program(input) {
+pub trait ProgramVisitorDirector<'a>: VisitorDirector<'a> + StatementVisitorDirector<'a> {
+    fn visit_program(&mut self, input: &'a Program) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_program(input) {
             input
                 .functions
                 .values()
@@ -160,8 +178,8 @@ impl<'a, V: ExpressionVisitor<'a> + ProgramVisitor<'a> + StatementVisitor<'a>> V
         }
     }
 
-    pub fn visit_function(&mut self, input: &'a Function) {
-        if let VisitResult::VisitChildren = self.visitor.visit_function(input) {
+    fn visit_function(&mut self, input: &'a Function) {
+        if let VisitResult::VisitChildren = self.visitor_ref().visit_function(input) {
             self.visit_block(&input.block);
         }
     }

compiler/passes/src/symbol_table/create.rs

@@ -36,7 +36,9 @@ impl<'a> CreateSymbolTable<'a> {
     }
 }
 
-impl<'a> ExpressionVisitor<'a> for CreateSymbolTable<'a> {}
+impl<'a> ExpressionVisitor<'a> for CreateSymbolTable<'a> {
+    type Output = ();
+}
 
 impl<'a> StatementVisitor<'a> for CreateSymbolTable<'a> {}
 

compiler/passes/src/symbol_table/director.rs

@@ -0,0 +1,52 @@
+// Copyright (C) 2019-2022 Aleo Systems Inc.
+// This file is part of the Leo library.
+
+// The Leo library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// The Leo library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with the Leo library. If not, see <https://www.gnu.org/licenses/>.
+
+use leo_ast::{ExpressionVisitorDirector, ProgramVisitorDirector, StatementVisitorDirector, VisitorDirector};
+use leo_errors::emitter::Handler;
+
+use crate::CreateSymbolTable;
+
+pub(crate) struct Director<'a> {
+    visitor: CreateSymbolTable<'a>,
+}
+
+impl<'a> Director<'a> {
+    pub(crate) fn new(handler: &'a Handler) -> Self {
+        Self {
+            visitor: CreateSymbolTable::new(handler),
+        }
+    }
+}
+
+impl<'a> VisitorDirector<'a> for Director<'a> {
+    type Visitor = CreateSymbolTable<'a>;
+
+    fn visitor(self) -> Self::Visitor {
+        self.visitor
+    }
+
+    fn visitor_ref(&mut self) -> &mut Self::Visitor {
+        &mut self.visitor
+    }
+}
+
+impl<'a> ExpressionVisitorDirector<'a> for Director<'a> {
+    type Output = ();
+}
+
+impl<'a> StatementVisitorDirector<'a> for Director<'a> {}
+
+impl<'a> ProgramVisitorDirector<'a> for Director<'a> {}

compiler/passes/src/symbol_table/mod.rs

@@ -17,6 +17,9 @@
 pub mod create;
 pub use create::*;
 
+pub mod director;
+use director::*;
+
 pub mod table;
 pub use table::*;
 
@@ -28,7 +31,7 @@ pub use variable_symbol::*;
 
 use crate::Pass;
 
-use leo_ast::{Ast, VisitorDirector};
+use leo_ast::{Ast, ProgramVisitorDirector, VisitorDirector};
 use leo_errors::{emitter::Handler, Result};
 
 impl<'a> Pass<'a> for CreateSymbolTable<'a> {
@@ -36,7 +39,7 @@ impl<'a> Pass<'a> for CreateSymbolTable<'a> {
     type Output = Result<SymbolTable<'a>>;
 
     fn do_pass((ast, handler): Self::Input) -> Self::Output {
-        let mut visitor = VisitorDirector::new(CreateSymbolTable::new(handler));
+        let mut visitor = Director::new(handler);
         visitor.visit_program(ast.as_repr());
         handler.last_err()?;
 

compiler/passes/src/type_checker/check_expressions.rs

@@ -16,7 +16,6 @@
 
 use leo_ast::*;
 use leo_errors::TypeCheckerError;
-use leo_span::Span;
 
 use crate::TypeChecker;
 
@@ -38,22 +37,29 @@ fn return_incorrect_type(t1: Option<Type>, t2: Option<Type>, expected: Option<Ty
     }
 }
 
-impl<'a> TypeChecker<'a> {
-    pub(crate) fn compare_expr_type(&mut self, expr: &Expression, expected: Option<Type>, span: Span) -> Option<Type> {
-        match expr {
-            Expression::Identifier(ident) => {
-                if let Some(var) = self.symbol_table.lookup_variable(&ident.name) {
-                    Some(self.assert_type(*var.type_, expected, span))
+impl<'a> ExpressionVisitor<'a> for TypeChecker<'a> {
+    type Output = Type;
+
+    fn visit_identifier(&mut self, input: &'a Identifier) -> (VisitResult, Option<Self::Output>) {
+        let type_ = if let Some(var) = self.symbol_table.lookup_variable(&input.name) {
+            Some(self.assert_type(*var.type_, self.expected_type))
         } else {
             self.handler
-                        .emit_err(TypeCheckerError::unknown_sym("variable", ident.name, span).into());
+                .emit_err(TypeCheckerError::unknown_sym("variable", input.name, self.span).into());
             None
+        };
+
+        (VisitResult::VisitChildren, type_)
     }
-            }
-            Expression::Value(value) => match value {
-                ValueExpression::Address(_, _) => Some(self.assert_type(Type::Address, expected, value.span())),
-                ValueExpression::Boolean(_, _) => Some(self.assert_type(Type::Boolean, expected, value.span())),
-                ValueExpression::Field(_, _) => Some(self.assert_type(Type::Field, expected, value.span())),
+
+    fn visit_value(&mut self, input: &'a ValueExpression) -> (VisitResult, Option<Self::Output>) {
+        let prev_span = self.span;
+        self.span = input.span();
+
+        let type_ = Some(match input {
+            ValueExpression::Address(_, _) => self.assert_type(Type::Address, self.expected_type),
+            ValueExpression::Boolean(_, _) => self.assert_type(Type::Boolean, self.expected_type),
+            ValueExpression::Field(_, _) => self.assert_type(Type::Field, self.expected_type),
             ValueExpression::Integer(type_, str_content, _) => {
                 match type_ {
                     IntegerType::I8 => {
@@ -65,7 +71,7 @@ impl<'a> TypeChecker<'a> {
 
                         if int.parse::<i8>().is_err() {
                             self.handler
-                                    .emit_err(TypeCheckerError::invalid_int_value(int, "i8", value.span()).into());
+                                .emit_err(TypeCheckerError::invalid_int_value(int, "i8", input.span()).into());
                         }
                     }
                     IntegerType::I16 => {
@@ -77,7 +83,7 @@ impl<'a> TypeChecker<'a> {
 
                         if int.parse::<i16>().is_err() {
                             self.handler
-                                    .emit_err(TypeCheckerError::invalid_int_value(int, "i16", value.span()).into());
+                                .emit_err(TypeCheckerError::invalid_int_value(int, "i16", input.span()).into());
                         }
                     }
                     IntegerType::I32 => {
@@ -89,7 +95,7 @@ impl<'a> TypeChecker<'a> {
 
                         if int.parse::<i32>().is_err() {
                             self.handler
-                                    .emit_err(TypeCheckerError::invalid_int_value(int, "i32", value.span()).into());
+                                .emit_err(TypeCheckerError::invalid_int_value(int, "i32", input.span()).into());
                         }
                     }
                     IntegerType::I64 => {
@@ -101,7 +107,7 @@ impl<'a> TypeChecker<'a> {
 
                         if int.parse::<i64>().is_err() {
                             self.handler
-                                    .emit_err(TypeCheckerError::invalid_int_value(int, "i64", value.span()).into());
+                                .emit_err(TypeCheckerError::invalid_int_value(int, "i64", input.span()).into());
                         }
                     }
                     IntegerType::I128 => {
@@ -113,120 +119,129 @@ impl<'a> TypeChecker<'a> {
 
                         if int.parse::<i128>().is_err() {
                             self.handler
-                                    .emit_err(TypeCheckerError::invalid_int_value(int, "i128", value.span()).into());
+                                .emit_err(TypeCheckerError::invalid_int_value(int, "i128", input.span()).into());
                         }
                     }
                     IntegerType::U8 if str_content.parse::<u8>().is_err() => self
                         .handler
-                            .emit_err(TypeCheckerError::invalid_int_value(str_content, "u8", value.span()).into()),
+                        .emit_err(TypeCheckerError::invalid_int_value(str_content, "u8", input.span()).into()),
                     IntegerType::U16 if str_content.parse::<u16>().is_err() => self
                         .handler
-                            .emit_err(TypeCheckerError::invalid_int_value(str_content, "u16", value.span()).into()),
+                        .emit_err(TypeCheckerError::invalid_int_value(str_content, "u16", input.span()).into()),
                     IntegerType::U32 if str_content.parse::<u32>().is_err() => self
                         .handler
-                            .emit_err(TypeCheckerError::invalid_int_value(str_content, "u32", value.span()).into()),
+                        .emit_err(TypeCheckerError::invalid_int_value(str_content, "u32", input.span()).into()),
                     IntegerType::U64 if str_content.parse::<u64>().is_err() => self
                         .handler
-                            .emit_err(TypeCheckerError::invalid_int_value(str_content, "u64", value.span()).into()),
+                        .emit_err(TypeCheckerError::invalid_int_value(str_content, "u64", input.span()).into()),
                     IntegerType::U128 if str_content.parse::<u128>().is_err() => self
                         .handler
-                            .emit_err(TypeCheckerError::invalid_int_value(str_content, "u128", value.span()).into()),
+                        .emit_err(TypeCheckerError::invalid_int_value(str_content, "u128", input.span()).into()),
                     _ => {}
                 }
-                    Some(self.assert_type(Type::IntegerType(*type_), expected, value.span()))
+                self.assert_type(Type::IntegerType(*type_), self.expected_type)
             }
-                ValueExpression::Group(_) => Some(self.assert_type(Type::Group, expected, value.span())),
-                ValueExpression::Scalar(_, _) => Some(self.assert_type(Type::Scalar, expected, value.span())),
+            ValueExpression::Group(_) => self.assert_type(Type::Group, self.expected_type),
+            ValueExpression::Scalar(_, _) => self.assert_type(Type::Scalar, self.expected_type),
             ValueExpression::String(_, _) => unreachable!("String types are not reachable"),
-            },
-            Expression::Binary(binary) => match binary.op {
-                BinaryOperation::And | BinaryOperation::Or => {
-                    self.assert_type(Type::Boolean, expected, binary.span());
-                    let t1 = self.compare_expr_type(&binary.left, expected, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, expected, binary.right.span());
+        });
 
-                    return_incorrect_type(t1, t2, expected)
+        self.span = prev_span;
+        (VisitResult::VisitChildren, type_)
+    }
+
+    fn visit_binary(&mut self, input: &'a BinaryExpression) -> (VisitResult, Option<Self::Output>) {
+        let prev_span = self.span;
+        self.span = input.span();
+
+        /* let type_ = match input.op {
+            BinaryOperation::And | BinaryOperation::Or => {
+                self.assert_type(Type::Boolean, self.expected_type);
+                let t1 = self.compare_expr_type(&input.left, self.expected_type, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, self.expected_type, input.right.span());
+
+                return_incorrect_type(t1, t2, self.expected_type)
             }
             BinaryOperation::Add => {
-                    self.assert_field_group_scalar_int_type(expected, binary.span());
-                    let t1 = self.compare_expr_type(&binary.left, expected, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, expected, binary.right.span());
+                self.assert_field_group_scalar_int_type(self.expected_type, input.span());
+                let t1 = self.compare_expr_type(&input.left, self.expected_type, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, self.expected_type, input.right.span());
 
-                    return_incorrect_type(t1, t2, expected)
+                return_incorrect_type(t1, t2, self.expected_type)
             }
             BinaryOperation::Sub => {
-                    self.assert_field_group_int_type(expected, binary.span());
-                    let t1 = self.compare_expr_type(&binary.left, expected, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, expected, binary.right.span());
+                self.assert_field_group_int_type(self.expected_type, input.span());
+                let t1 = self.compare_expr_type(&input.left, self.expected_type, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, self.expected_type, input.right.span());
 
-                    return_incorrect_type(t1, t2, expected)
+                return_incorrect_type(t1, t2, self.expected_type)
             }
             BinaryOperation::Mul => {
-                    self.assert_field_group_int_type(expected, binary.span());
+                self.assert_field_group_int_type(self.expected_type, input.span());
 
-                    let t1 = self.compare_expr_type(&binary.left, None, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, None, binary.right.span());
+                let t1 = self.compare_expr_type(&input.left, None, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, None, input.right.span());
 
                 // Allow `group` * `scalar` multiplication.
                 match (t1.as_ref(), t2.as_ref()) {
                     (Some(Type::Group), Some(other)) => {
-                            self.assert_type(Type::Group, expected, binary.left.span());
-                            self.assert_type(*other, Some(Type::Scalar), binary.span());
+                        self.assert_type(Type::Group, self.expected_type);
+                        self.assert_type(*other, Some(Type::Scalar));
                         Some(Type::Group)
                     }
                     (Some(other), Some(Type::Group)) => {
-                            self.assert_type(Type::Group, expected, binary.left.span());
-                            self.assert_type(*other, Some(Type::Scalar), binary.span());
+                        self.assert_type(Type::Group, self.expected_type);
+                        self.assert_type(*other, Some(Type::Scalar));
                         Some(Type::Group)
                     }
                     _ => {
-                            self.assert_type(t1.unwrap(), expected, binary.left.span());
-                            self.assert_type(t2.unwrap(), expected, binary.right.span());
-                            return_incorrect_type(t1, t2, expected)
+                        self.assert_type(t1.unwrap(), self.expected_type);
+                        self.assert_type(t2.unwrap(), self.expected_type);
+                        return_incorrect_type(t1, t2, self.expected_type)
                     }
                 }
             }
             BinaryOperation::Div => {
-                    self.assert_field_int_type(expected, binary.span());
+                self.assert_field_int_type(self.expected_type, input.span());
 
-                    let t1 = self.compare_expr_type(&binary.left, expected, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, expected, binary.right.span());
-                    return_incorrect_type(t1, t2, expected)
+                let t1 = self.compare_expr_type(&input.left, self.expected_type, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, self.expected_type, input.right.span());
+                return_incorrect_type(t1, t2, self.expected_type)
             }
             BinaryOperation::Pow => {
-                    let t1 = self.compare_expr_type(&binary.left, None, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, None, binary.right.span());
+                let t1 = self.compare_expr_type(&input.left, None, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, None, input.right.span());
 
                 match (t1.as_ref(), t2.as_ref()) {
                     // Type A must be an int.
                     // Type B must be a unsigned int.
                     (Some(Type::IntegerType(_)), Some(Type::IntegerType(itype))) if !itype.is_signed() => {
-                            self.assert_type(t1.unwrap(), expected, binary.span());
+                        self.assert_type(t1.unwrap(), self.expected_type);
                     }
                     // Type A was an int.
                     // But Type B was not a unsigned int.
                     (Some(Type::IntegerType(_)), Some(t)) => {
                         self.handler.emit_err(
-                                TypeCheckerError::incorrect_pow_exponent_type("unsigned int", t, binary.right.span())
+                            TypeCheckerError::incorrect_pow_exponent_type("unsigned int", t, input.right.span())
                                 .into(),
                         );
                     }
                     // Type A must be a field.
                     // Type B must be an int.
                     (Some(Type::Field), Some(Type::IntegerType(_))) => {
-                            self.assert_type(Type::Field, expected, binary.span());
+                        self.assert_type(Type::Field, self.expected_type);
                     }
                     // Type A was a field.
                     // But Type B was not an int.
                     (Some(Type::Field), Some(t)) => {
                         self.handler.emit_err(
-                                TypeCheckerError::incorrect_pow_exponent_type("int", t, binary.right.span()).into(),
+                            TypeCheckerError::incorrect_pow_exponent_type("int", t, input.right.span()).into(),
                         );
                     }
                     // The base is some type thats not an int or field.
                     (Some(t), _) => {
                         self.handler
-                                .emit_err(TypeCheckerError::incorrect_pow_base_type(t, binary.left.span()).into());
+                            .emit_err(TypeCheckerError::incorrect_pow_base_type(t, input.left.span()).into());
                     }
                     _ => {}
                 }
@@ -234,96 +249,27 @@ impl<'a> TypeChecker<'a> {
                 t1
             }
             BinaryOperation::Eq | BinaryOperation::Ne => {
-                    let t1 = self.compare_expr_type(&binary.left, None, binary.left.span());
-                    let t2 = self.compare_expr_type(&binary.right, None, binary.right.span());
+                let t1 = self.compare_expr_type(&input.left, None, input.left.span());
+                let t2 = self.compare_expr_type(&input.right, None, input.right.span());
 
-                    self.assert_eq_types(t1, t2, binary.span());
+                self.assert_eq_types(t1, t2, input.span());
 
                 Some(Type::Boolean)
             }
             BinaryOperation::Lt | BinaryOperation::Gt | BinaryOperation::Le | BinaryOperation::Ge => {
-                    let t1 = self.compare_expr_type(&binary.left, None, binary.left.span());
-                    self.assert_field_scalar_int_type(t1, binary.left.span());
+                let t1 = self.compare_expr_type(&input.left, None, input.left.span());
+                self.assert_field_scalar_int_type(t1, input.left.span());
 
-                    let t2 = self.compare_expr_type(&binary.right, None, binary.right.span());
-                    self.assert_field_scalar_int_type(t2, binary.right.span());
+                let t2 = self.compare_expr_type(&input.right, None, input.right.span());
+                self.assert_field_scalar_int_type(t2, input.right.span());
 
-                    self.assert_eq_types(t1, t2, binary.span());
+                self.assert_eq_types(t1, t2, input.span());
 
                 Some(Type::Boolean)
             }
-            },
-            Expression::Unary(unary) => match unary.op {
-                UnaryOperation::Not => {
-                    self.assert_type(Type::Boolean, expected, unary.span());
-                    self.compare_expr_type(&unary.inner, expected, unary.inner.span())
-                }
-                UnaryOperation::Negate => {
-                    let prior_negate_state = self.negate;
-                    self.negate = true;
-                    let type_ = self.compare_expr_type(&unary.inner, expected, unary.inner.span());
-                    self.negate = prior_negate_state;
-                    match type_.as_ref() {
-                        Some(
-                            Type::IntegerType(
-                                IntegerType::I8
-                                | IntegerType::I16
-                                | IntegerType::I32
-                                | IntegerType::I64
-                                | IntegerType::I128,
-                            )
-                            | Type::Field
-                            | Type::Group,
-                        ) => {}
-                        Some(t) => self
-                            .handler
-                            .emit_err(TypeCheckerError::type_is_not_negatable(t, unary.inner.span()).into()),
-                        _ => {}
-                    };
-                    type_
-                }
-            },
-            Expression::Ternary(ternary) => {
-                self.compare_expr_type(&ternary.condition, Some(Type::Boolean), ternary.condition.span());
-                let t1 = self.compare_expr_type(&ternary.if_true, expected, ternary.if_true.span());
-                let t2 = self.compare_expr_type(&ternary.if_false, expected, ternary.if_false.span());
-                return_incorrect_type(t1, t2, expected)
-            }
-            Expression::Call(call) => match &*call.function {
-                Expression::Identifier(ident) => {
-                    if let Some(func) = self.symbol_table.lookup_fn(&ident.name) {
-                        let ret = self.assert_type(func.output, expected, ident.span());
+        }; */
 
-                        if func.input.len() != call.arguments.len() {
-                            self.handler.emit_err(
-                                TypeCheckerError::incorrect_num_args_to_call(
-                                    func.input.len(),
-                                    call.arguments.len(),
-                                    call.span(),
-                                )
-                                .into(),
-                            );
-                        }
-
-                        func.input
-                            .iter()
-                            .zip(call.arguments.iter())
-                            .for_each(|(expected, argument)| {
-                                self.compare_expr_type(argument, Some(expected.get_variable().type_), argument.span());
-                            });
-
-                        Some(ret)
-                    } else {
-                        self.handler
-                            .emit_err(TypeCheckerError::unknown_sym("function", &ident.name, ident.span()).into());
-                        None
+        self.span = prev_span;
+        (VisitResult::VisitChildren, None)
     }
 }
-                expr => self.compare_expr_type(expr, expected, call.span()),
-            },
-            Expression::Err(_) => None,
-        }
-    }
-}
-
-impl<'a> ExpressionVisitor<'a> for TypeChecker<'a> {}

compiler/passes/src/type_checker/check_statements.rs

@@ -27,7 +27,7 @@ impl<'a> StatementVisitor<'a> for TypeChecker<'a> {
 
         // Would never be None.
         let func_output_type = self.symbol_table.lookup_fn(&parent).map(|f| f.output);
-        self.compare_expr_type(&input.expression, func_output_type, input.expression.span());
+        // self.compare_expr_type(&input.expression, func_output_type, input.expression.span());
 
         VisitResult::VisitChildren
     }
@@ -51,7 +51,7 @@ impl<'a> StatementVisitor<'a> for TypeChecker<'a> {
                 self.handler.emit_err(err);
             }
 
-            self.compare_expr_type(&input.value, Some(input.type_), input.value.span());
+            // self.compare_expr_type(&input.value, Some(input.type_), input.value.span());
         });
 
         VisitResult::VisitChildren
@@ -80,14 +80,14 @@ impl<'a> StatementVisitor<'a> for TypeChecker<'a> {
         };
 
         if var_type.is_some() {
-            self.compare_expr_type(&input.value, var_type, input.value.span());
+            // self.compare_expr_type(&input.value, var_type, input.value.span());
         }
 
         VisitResult::VisitChildren
     }
 
     fn visit_conditional(&mut self, input: &'a ConditionalStatement) -> VisitResult {
-        self.compare_expr_type(&input.condition, Some(Type::Boolean), input.condition.span());
+        // self.compare_expr_type(&input.condition, Some(Type::Boolean), input.condition.span());
 
         VisitResult::VisitChildren
     }
@@ -104,8 +104,8 @@ impl<'a> StatementVisitor<'a> for TypeChecker<'a> {
             self.handler.emit_err(err);
         }
 
-        self.compare_expr_type(&input.start, Some(input.type_), input.start.span());
-        self.compare_expr_type(&input.stop, Some(input.type_), input.stop.span());
+        // self.compare_expr_type(&input.start, Some(input.type_), input.start.span());
+        // self.compare_expr_type(&input.stop, Some(input.type_), input.stop.span());
 
         VisitResult::VisitChildren
     }
@@ -113,7 +113,7 @@ impl<'a> StatementVisitor<'a> for TypeChecker<'a> {
     fn visit_console(&mut self, input: &'a ConsoleStatement) -> VisitResult {
         match &input.function {
             ConsoleFunction::Assert(expr) => {
-                self.compare_expr_type(expr, Some(Type::Boolean), expr.span());
+                // self.compare_expr_type(expr, Some(Type::Boolean), expr.span());
             }
             ConsoleFunction::Error(_) | ConsoleFunction::Log(_) => {
                 // TODO: undetermined

compiler/passes/src/type_checker/checker.rs

@@ -25,6 +25,8 @@ pub struct TypeChecker<'a> {
     pub(crate) handler: &'a Handler,
     pub(crate) parent: Option<Symbol>,
     pub(crate) negate: bool,
+    pub(crate) expected_type: Option<Type>,
+    pub(crate) span: Span,
 }
 
 const INT_TYPES: [Type; 10] = [
@@ -74,6 +76,8 @@ impl<'a> TypeChecker<'a> {
             handler,
             parent: None,
             negate: false,
+            expected_type: None,
+            span: Default::default(),
         }
     }
 
@@ -91,11 +95,11 @@ impl<'a> TypeChecker<'a> {
     }
 
     /// Returns the given type if it equals the expected type or the expected type is none.
-    pub(crate) fn assert_type(&self, type_: Type, expected: Option<Type>, span: Span) -> Type {
+    pub(crate) fn assert_type(&mut self, type_: Type, expected: Option<Type>) -> Type {
         if let Some(expected) = expected {
             if type_ != expected {
                 self.handler
-                    .emit_err(TypeCheckerError::type_should_be(type_, expected, span).into());
+                    .emit_err(TypeCheckerError::type_should_be(type_, expected, self.span).into());
             }
         }
 

compiler/passes/src/type_checker/director.rs

@@ -0,0 +1,200 @@
+// Copyright (C) 2019-2022 Aleo Systems Inc.
+// This file is part of the Leo library.
+
+// The Leo library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// The Leo library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with the Leo library. If not, see <https://www.gnu.org/licenses/>.
+
+use leo_ast::*;
+use leo_errors::{emitter::Handler, TypeCheckerError};
+
+use crate::{SymbolTable, TypeChecker};
+
+pub(crate) struct Director<'a> {
+    visitor: TypeChecker<'a>,
+}
+
+impl<'a> Director<'a> {
+    pub(crate) fn new(symbol_table: &'a mut SymbolTable<'a>, handler: &'a Handler) -> Self {
+        Self {
+            visitor: TypeChecker::new(symbol_table, handler),
+        }
+    }
+}
+
+impl<'a> VisitorDirector<'a> for Director<'a> {
+    type Visitor = TypeChecker<'a>;
+
+    fn visitor(self) -> Self::Visitor {
+        self.visitor
+    }
+
+    fn visitor_ref(&mut self) -> &mut Self::Visitor {
+        &mut self.visitor
+    }
+}
+
+fn return_incorrect_type(t1: Option<Type>, t2: Option<Type>, expected: Option<Type>) -> Option<Type> {
+    match (t1, t2) {
+        (Some(t1), Some(t2)) if t1 == t2 => Some(t1),
+        (Some(t1), Some(t2)) => {
+            if let Some(expected) = expected {
+                if t1 != expected {
+                    Some(t1)
+                } else {
+                    Some(t2)
+                }
+            } else {
+                Some(t1)
+            }
+        }
+        (None, Some(_)) | (Some(_), None) | (None, None) => None,
+    }
+}
+
+impl<'a> ExpressionVisitorDirector<'a> for Director<'a> {
+    type Output = Type;
+
+    fn visit_expression(&mut self, input: &'a Expression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor.visit_expression(input).0 {
+            return match input {
+                Expression::Identifier(expr) => self.visit_identifier(expr),
+                Expression::Value(expr) => self.visit_value(expr),
+                Expression::Binary(expr) => self.visit_binary(expr),
+                Expression::Unary(expr) => self.visit_unary(expr),
+                Expression::Ternary(expr) => self.visit_ternary(expr),
+                Expression::Call(expr) => self.visit_call(expr),
+                Expression::Err(expr) => self.visit_err(expr),
+            };
+        }
+
+        None
+    }
+
+    fn visit_identifier(&mut self, input: &'a Identifier) -> Option<Self::Output> {
+        self.visitor.visit_identifier(input).1
+    }
+
+    fn visit_value(&mut self, input: &'a ValueExpression) -> Option<Self::Output> {
+        self.visitor.visit_value(input).1
+    }
+
+    fn visit_binary(&mut self, input: &'a BinaryExpression) -> Option<Self::Output> {
+        match self.visitor.visit_binary(input) {
+            (VisitResult::VisitChildren, expected) => {
+                let t1 = self.visit_expression(&input.left);
+                let t2 = self.visit_expression(&input.right);
+
+                return_incorrect_type(t1, t2, self.visitor.expected_type)
+            }
+            _ => None,
+        }
+    }
+
+    fn visit_unary(&mut self, input: &'a UnaryExpression) -> Option<Self::Output> {
+        match input.op {
+            UnaryOperation::Not => {
+                self.visitor.assert_type(Type::Boolean, self.visitor.expected_type);
+                self.visit_expression(&input.inner)
+            }
+            UnaryOperation::Negate => {
+                let prior_negate_state = self.visitor.negate;
+                self.visitor.negate = true;
+
+                let type_ = self.visit_expression(&input.inner);
+                self.visitor.negate = prior_negate_state;
+                match type_.as_ref() {
+                    Some(
+                        Type::IntegerType(
+                            IntegerType::I8
+                            | IntegerType::I16
+                            | IntegerType::I32
+                            | IntegerType::I64
+                            | IntegerType::I128,
+                        )
+                        | Type::Field
+                        | Type::Group,
+                    ) => {}
+                    Some(t) => self
+                        .visitor
+                        .handler
+                        .emit_err(TypeCheckerError::type_is_not_negatable(t, input.inner.span()).into()),
+                    _ => {}
+                };
+                type_
+            }
+        }
+    }
+
+    fn visit_ternary(&mut self, input: &'a TernaryExpression) -> Option<Self::Output> {
+        if let VisitResult::VisitChildren = self.visitor.visit_ternary(input).0 {
+            let prev_expected_type = self.visitor.expected_type;
+            self.visitor.expected_type = Some(Type::Boolean);
+            self.visit_expression(&input.condition);
+            self.visitor.expected_type = prev_expected_type;
+
+            let t1 = self.visit_expression(&input.if_true);
+            let t2 = self.visit_expression(&input.if_false);
+
+            return return_incorrect_type(t1, t2, self.visitor.expected_type);
+        }
+
+        None
+    }
+
+    fn visit_call(&mut self, input: &'a CallExpression) -> Option<Self::Output> {
+        match &*input.function {
+            Expression::Identifier(ident) => {
+                if let Some(func) = self.visitor.symbol_table.clone().lookup_fn(&ident.name) {
+                    let ret = self.visitor.assert_type(func.output, self.visitor.expected_type);
+
+                    if func.input.len() != input.arguments.len() {
+                        self.visitor.handler.emit_err(
+                            TypeCheckerError::incorrect_num_args_to_call(
+                                func.input.len(),
+                                input.arguments.len(),
+                                input.span(),
+                            )
+                            .into(),
+                        );
+                    }
+
+                    func.input
+                        .iter()
+                        .zip(input.arguments.iter())
+                        .for_each(|(expected, argument)| {
+                            let prev_expected_type = self.visitor.expected_type;
+                            self.visitor.expected_type = Some(expected.get_variable().type_);
+                            self.visit_expression(argument);
+                            self.visitor.expected_type = prev_expected_type;
+                        });
+
+                    Some(ret)
+                } else {
+                    self.visitor
+                        .handler
+                        .emit_err(TypeCheckerError::unknown_sym("function", &ident.name, ident.span()).into());
+                    None
+                }
+            }
+            expr => self.visit_expression(expr),
+        }
+    }
+
+    fn visit_err(&mut self, input: &'a ErrExpression) -> Option<Self::Output> {
+        self.visitor.visit_err(input).1
+    }
+}
+
+impl<'a> StatementVisitorDirector<'a> for Director<'a> {}
+
+impl<'a> ProgramVisitorDirector<'a> for Director<'a> {}

compiler/passes/src/type_checker/mod.rs

@@ -26,9 +26,12 @@ pub use check_statements::*;
 pub mod checker;
 pub use checker::*;
 
+pub mod director;
+use director::*;
+
 use crate::{Pass, SymbolTable};
 
-use leo_ast::{Ast, VisitorDirector};
+use leo_ast::{Ast, ProgramVisitorDirector};
 use leo_errors::{emitter::Handler, Result};
 
 impl<'a> Pass<'a> for TypeChecker<'a> {
@@ -36,7 +39,7 @@ impl<'a> Pass<'a> for TypeChecker<'a> {
     type Output = Result<()>;
 
     fn do_pass((ast, symbol_table, handler): Self::Input) -> Self::Output {
-        let mut visitor = VisitorDirector::new(TypeChecker::new(symbol_table, handler));
+        let mut visitor = Director::new(symbol_table, handler);
         visitor.visit_program(ast.as_repr());
         handler.last_err()?;