Add eval_expression_tree_raw.

CHANGELOG.md

@@ -13,6 +13,7 @@ Enhancements
 ------------
 
 * `switch` cases can now include multiple values separated by `|`.
+* `EvalContext::eval_expression_tree_raw` and `Expression::eval_with_context_raw` are added to allow for not rewinding the `Scope` at the end of a statements block.
 
 
 Version 1.8.0

src/api/call_fn.rs

@@ -185,6 +185,10 @@ impl Engine {
     ///
     /// Not available under `no_function`.
     ///
+    /// # WARNING - Unstable API
+    ///
+    /// This API is volatile and may change in the future.
+    ///
     /// # WARNING - Low Level API
     ///
     /// This function is _extremely_ low level.
@@ -202,6 +206,7 @@ impl Engine {
     /// Do not use the arguments after this call. If they are needed afterwards, clone them _before_
     /// calling this function.
     #[cfg(feature = "internals")]
+    #[deprecated = "This API is NOT deprecated, but it is considered volatile and may change in the future."]
     #[inline(always)]
     pub fn call_fn_raw_raw(
         &self,

src/api/custom_syntax.rs

@@ -74,6 +74,28 @@ impl Expression<'_> {
     pub fn eval_with_context(&self, context: &mut EvalContext) -> RhaiResult {
         context.eval_expression_tree(self)
     }
+    /// Evaluate this [expression tree][Expression] within an [evaluation context][`EvalContext`].
+    ///
+    /// The following option is available:
+    ///
+    /// * whether to rewind the [`Scope`] after evaluation if the expression is a [`StmtBlock`][crate::ast::StmtBlock]
+    ///
+    /// # WARNING - Unstable API
+    ///
+    /// This API is volatile and may change in the future.
+    ///
+    /// # WARNING - Low Level API
+    ///
+    /// This function is _extremely_ low level.  It evaluates an expression from an [`AST`][crate::AST].
+    #[inline(always)]
+    pub fn eval_with_context_raw(
+        &self,
+        context: &mut EvalContext,
+        rewind_scope: bool,
+    ) -> RhaiResult {
+        #[allow(deprecated)]
+        context.eval_expression_tree_raw(self, rewind_scope)
+    }
     /// Get the value of this expression if it is a variable name or a string constant.
     ///
     /// Returns [`None`] also if the constant is not of the specified type.

src/eval/eval_context.rs

@@ -150,6 +150,32 @@ impl<'a, 's, 'ps, 'g, 'pg, 'c, 'pc, 't, 'pt> EvalContext<'a, 's, 'ps, 'g, 'pg, '
     #[cfg(not(feature = "no_custom_syntax"))]
     #[inline(always)]
     pub fn eval_expression_tree(&mut self, expr: &crate::Expression) -> crate::RhaiResult {
+        #[allow(deprecated)]
+        self.eval_expression_tree_raw(expr, true)
+    }
+    /// Evaluate an [expression tree][crate::Expression] within this [evaluation context][`EvalContext`].
+    ///
+    /// The following option is available:
+    ///
+    /// * whether to rewind the [`Scope`] after evaluation if the expression is a [`StmtBlock`][crate::ast::StmtBlock]
+    ///
+    /// # WARNING - Unstable API
+    ///
+    /// This API is volatile and may change in the future.
+    ///
+    /// # WARNING - Low Level API
+    ///
+    /// This function is _extremely_ low level.  It evaluates an expression from an [`AST`][crate::AST].
+    #[cfg(not(feature = "no_custom_syntax"))]
+    #[deprecated = "This API is NOT deprecated, but it is considered volatile and may change in the future."]
+    #[inline]
+    pub fn eval_expression_tree_raw(
+        &mut self,
+        expr: &crate::Expression,
+        rewind_scope: bool,
+    ) -> crate::RhaiResult {
+        let expr: &crate::ast::Expr = expr;
+
         let mut new_caches = Caches::new();
 
         let caches = match self.caches.as_mut() {
@@ -157,7 +183,18 @@ impl<'a, 's, 'ps, 'g, 'pg, 'c, 'pc, 't, 'pt> EvalContext<'a, 's, 'ps, 'g, 'pg, '
             None => &mut new_caches,
         };
 
-        self.engine.eval_expr(
+        match expr {
+            crate::Expr::Stmt(statements) => self.engine.eval_stmt_block(
+                self.scope,
+                self.global,
+                caches,
+                self.lib,
+                self.this_ptr,
+                &statements,
+                rewind_scope,
+                self.level,
+            ),
+            _ => self.engine.eval_expr(
                 self.scope,
                 self.global,
                 caches,
@@ -165,6 +202,7 @@ impl<'a, 's, 'ps, 'g, 'pg, 'c, 'pc, 't, 'pt> EvalContext<'a, 's, 'ps, 'g, 'pg, '
                 self.this_ptr,
                 expr,
                 self.level,
-        )
+            ),
+        }
     }
 }

src/optimizer.rs

@@ -1236,7 +1236,7 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
             if x.scope_may_be_changed {
                 state.propagate_constants = false;
             }
-            x.inputs.iter_mut().for_each(|expr| optimize_expr(expr, state, false));
+            // Do not optimize custom syntax expressions as you won't know how they would be called
         }
 
         // All other expressions - skip

tests/custom_syntax.rs

@@ -52,7 +52,13 @@ fn test_custom_syntax() -> Result<(), Box<EvalAltResult>> {
                     break;
                 }
 
+                // Do not rewind if the variable is upper-case
+                if var_name.to_uppercase() == var_name {
+                    context.eval_expression_tree_raw(stmt, false)?;
+                } else {
                     context.eval_expression_tree(stmt)?;
+                }
+
                 count += 1;
 
                 context
@@ -125,6 +131,26 @@ fn test_custom_syntax() -> Result<(), Box<EvalAltResult>> {
         )?,
         144
     );
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                let foo = 123;
+                exec [x<15] -> { let foo = x; x += 1; } while x < 42;
+                foo
+            "
+        )?,
+        123
+    );
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                let foo = 123;
+                exec [ABC<15] -> { let foo = ABC; ABC += 1; } while ABC < 42;
+                foo
+            "
+        )?,
+        14
+    );
 
     // The first symbol must be an identifier
     assert_eq!(