Better encapsulate EvalContext.

src/api/custom_syntax.rs

@@ -1,7 +1,6 @@
 //! Module implementing custom syntax for [`Engine`].
 
 use crate::ast::Expr;
-use crate::eval::Caches;
 use crate::func::native::SendSync;
 use crate::parser::ParseResult;
 use crate::tokenizer::{is_valid_identifier, Token};
@@ -140,34 +139,6 @@ impl Deref for Expression<'_> {
     }
 }
 
-impl EvalContext<'_, '_, '_, '_, '_, '_, '_, '_> {
-    /// Evaluate an [expression tree][Expression] within this [evaluation context][`EvalContext`].
-    ///
-    /// # WARNING - Low Level API
-    ///
-    /// This function is very low level.  It evaluates an expression from an [`AST`][crate::AST].
-    #[inline(always)]
-    pub fn eval_expression_tree(&mut self, expr: &Expression) -> RhaiResult {
-        let mut caches;
-
-        self.engine.eval_expr(
-            self.scope,
-            self.global,
-            match self.caches.as_mut() {
-                Some(c) => c,
-                None => {
-                    caches = Caches::new();
-                    &mut caches
-                }
-            },
-            self.lib,
-            self.this_ptr,
-            expr,
-            self.level,
-        )
-    }
-}
-
 /// Definition of a custom syntax definition.
 pub struct CustomSyntax {
     /// A parsing function to return the next token in a custom syntax based on the