Start turning AirTree statements into expressions (let)

Still many places to fix, WIP.

crates/aiken-lang/src/gen_uplc/builder.rs

@@ -659,10 +659,7 @@ pub fn erase_opaque_type_operations(
 /// Determine whether this air_tree node introduces any shadowing over `potential_matches`
 pub fn find_introduced_variables(air_tree: &AirTree) -> Vec<String> {
     match air_tree {
-        AirTree::Statement {
-            statement: AirStatement::Let { name, .. },
-            ..
-        } => vec![name.clone()],
+        AirTree::Expression(AirExpression::Let { name, .. }) => vec![name.clone()],
         AirTree::Statement {
             statement: AirStatement::TupleGuard { indices, .. },
             ..

crates/aiken-lang/src/gen_uplc/tree.rs

@@ -117,11 +117,6 @@ pub enum AirTree {
 
 #[derive(Debug, Clone, PartialEq)]
 pub enum AirStatement {
-    // Assignment
-    Let {
-        name: String,
-        value: Box<AirTree>,
-    },
     DefineFunc {
         func_name: String,
         module_name: String,
@@ -209,6 +204,13 @@ pub enum AirStatement {
 
 #[derive(Debug, Clone, PartialEq)]
 pub enum AirExpression {
+    // Assignment
+    Let {
+        name: String,
+        value: Box<AirTree>,
+        then: Box<AirTree>,
+    },
+
     // Primitives
     Int {
         value: String,
@@ -494,14 +496,12 @@ impl AirTree {
             arg: arg.into(),
         })
     }
-    pub fn let_assignment(name: impl ToString, value: AirTree) -> AirTree {
-        AirTree::Statement {
-            statement: AirStatement::Let {
-                name: name.to_string(),
-                value: value.into(),
-            },
-            hoisted_over: None,
-        }
+    pub fn let_assignment(name: impl ToString, value: AirTree, then: AirTree) -> AirTree {
+        AirTree::Expression(AirExpression::Let {
+            name: name.to_string(),
+            value: value.into(),
+            then: then.into(),
+        })
     }
     pub fn cast_from_data(value: AirTree, tipo: Rc<Type>, msg: Option<AirMsg>) -> AirTree {
         AirTree::Expression(AirExpression::CastFromData {
@@ -755,6 +755,7 @@ impl AirTree {
             hoisted_over: None,
         }
     }
+
     pub fn list_access(
         names: Vec<String>,
         tipo: Rc<Type>,
@@ -889,8 +890,6 @@ impl AirTree {
             vec![head_list],
         );
 
-        let assign = AirTree::let_assignment("_", expect_on_head);
-
         let next_call = AirTree::call(
             AirTree::var(
                 ValueConstructor::public(
@@ -918,11 +917,13 @@ impl AirTree {
             ],
         );
 
+        let assign = AirTree::let_assignment("_", expect_on_head, next_call);
+
         AirTree::list_clause(
             "__list_to_check",
             void(),
             AirTree::void(),
-            assign.hoist_over(next_call),
+            assign,
             None,
             false,
         )
@@ -941,10 +942,6 @@ impl AirTree {
                 hoisted_over: Some(exp),
             } => {
                 match statement {
-                    AirStatement::Let { value, name } => {
-                        air_vec.push(Air::Let { name: name.clone() });
-                        value.create_air_vec(air_vec);
-                    }
                     AirStatement::DefineFunc {
                         func_name,
                         module_name,
@@ -1143,6 +1140,11 @@ impl AirTree {
                 exp.create_air_vec(air_vec);
             }
             AirTree::Expression(exp) => match exp {
+                AirExpression::Let { value, then, name } => {
+                    air_vec.push(Air::Let { name: name.clone() });
+                    value.create_air_vec(air_vec);
+                    then.create_air_vec(air_vec);
+                }
                 AirExpression::Int { value } => air_vec.push(Air::Int {
                     value: value.clone(),
                 }),
@@ -1517,9 +1519,10 @@ impl AirTree {
         let mut index_count = IndexCounter::new();
         tree_path.push(current_depth, depth_index);
 
-        if let AirTree::Statement { statement, .. } = self {
-            match statement {
-                AirStatement::Let { value, .. } => {
+        match self {
+            AirTree::UnhoistedSequence(..) => unreachable!("No unhoisted sequence at this point"),
+            AirTree::Expression(expr) => match expr {
+                AirExpression::Let { value, .. } => {
                     value.do_traverse_tree_with(
                         tree_path,
                         current_depth + 1,
@@ -1528,6 +1531,9 @@ impl AirTree {
                         apply_with_func_last,
                     );
                 }
+                _ => (),
+            },
+            AirTree::Statement { statement, .. } => match statement {
                 AirStatement::DefineFunc { func_body, .. } => {
                     func_body.do_traverse_tree_with(
                         tree_path,
@@ -1628,7 +1634,7 @@ impl AirTree {
                         apply_with_func_last,
                     );
                 }
-            };
+            },
         }
 
         if !apply_with_func_last {
@@ -1649,6 +1655,15 @@ impl AirTree {
                 );
             }
             AirTree::Expression(e) => match e {
+                AirExpression::Let { then, .. } => {
+                    then.do_traverse_tree_with(
+                        tree_path,
+                        current_depth + 1,
+                        index_count.next_number(),
+                        with,
+                        apply_with_func_last,
+                    );
+                }
                 AirExpression::List { items, .. } => {
                     for item in items {
                         item.do_traverse_tree_with(
@@ -1987,15 +2002,6 @@ impl AirTree {
                     statement,
                     hoisted_over: Some(hoisted_over),
                 } => match statement {
-                    AirStatement::Let { value, .. } => {
-                        if *index == 0 {
-                            value.as_mut().do_find_air_tree_node(tree_path_iter)
-                        } else if *index == 1 {
-                            hoisted_over.as_mut().do_find_air_tree_node(tree_path_iter)
-                        } else {
-                            panic!("Tree Path index outside tree children nodes")
-                        }
-                    }
                     AirStatement::AssertConstr { constr, .. } => {
                         if *index == 0 {
                             constr.as_mut().do_find_air_tree_node(tree_path_iter)
@@ -2100,6 +2106,15 @@ impl AirTree {
                     }
                 },
                 AirTree::Expression(e) => match e {
+                    AirExpression::Let { value, then, .. } => {
+                        if *index == 0 {
+                            value.as_mut().do_find_air_tree_node(tree_path_iter)
+                        } else if *index == 1 {
+                            then.as_mut().do_find_air_tree_node(tree_path_iter)
+                        } else {
+                            panic!("Tree Path index outside tree children nodes")
+                        }
+                    }
                     AirExpression::List { items, .. }
                     | AirExpression::Tuple { items, .. }
                     | AirExpression::Builtin { args: items, .. } => {