feat!: reduce stack usage by selectively wrapping large values in Box

This evens out some of the large enums' sizes (e.g. Expression and Statement's)
from over 200 bytes to <=144. Further reduction could be done, as this commit
only changes the obvious ones for now.

Also moves BinaryOperation's Box up one level so it only uses one Box.

src/expr.rs

@@ -14,7 +14,7 @@ pub enum Expression {
     Boolean(bool),
     /// List expressions are constructed by plain arrays containing of an arbitrary number of expressions.
     List(Cow<'static, [Expression]>),
-    BinaryOperation(BinaryOperation),
+    BinaryOperation(Box<BinaryOperation>),
     Range(Range),
 
     Named(NamedExpression),
@@ -327,23 +327,23 @@ pub enum FibFlag {
 pub enum BinaryOperation {
     #[serde(rename = "&")]
     /// Binary AND (`&`)
-    AND(Box<Expression>, Box<Expression>),
+    AND(Expression, Expression),
 
     #[serde(rename = "|")]
     /// Binary OR (`|`)
-    OR(Box<Expression>, Box<Expression>),
+    OR(Expression, Expression),
 
     #[serde(rename = "^")]
     /// Binary XOR (`^`)
-    XOR(Box<Expression>, Box<Expression>),
+    XOR(Expression, Expression),
 
     #[serde(rename = "<<")]
     /// Left shift (`<<`)
-    LSHIFT(Box<Expression>, Box<Expression>),
+    LSHIFT(Expression, Expression),
 
     #[serde(rename = ">>")]
     /// Right shift (`>>`)
-    RSHIFT(Box<Expression>, Box<Expression>),
+    RSHIFT(Expression, Expression),
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]

src/schema.rs

@@ -140,9 +140,9 @@ pub enum FlushObject {
     /// A chain to flush (i.e., remove all rules from chain).
     Chain(Chain),
     /// A set to flush (i.e., remove all elements from set).
-    Set(Set),
+    Set(Box<Set>),
     /// A map to flush (i.e., remove all elements from map).
-    Map(Map),
+    Map(Box<Map>),
     /// A meter to flush.
     Meter(Meter),
     /// Flush the live ruleset (i.e., remove all elements from live ruleset).
@@ -774,7 +774,7 @@ pub enum LimitUnit {
 pub struct Meter {
     pub name: Cow<'static, str>,
     pub key: Expression,
-    pub stmt: Statement,
+    pub stmt: Box<Statement>,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]