Run var def filter during parsing.

src/types/error.rs

@@ -36,6 +36,8 @@ pub enum EvalAltResult {
 
     /// Shadowing of an existing variable disallowed. Wrapped value is the variable name.
     ErrorVariableExists(String, Position),
+    /// Forbidden variable name. Wrapped value is the variable name.
+    ErrorForbiddenVariable(String, Position),
     /// Access of an unknown variable. Wrapped value is the variable name.
     ErrorVariableNotFound(String, Position),
     /// Access of an unknown object map property. Wrapped value is the property name.
@@ -148,6 +150,7 @@ impl fmt::Display for EvalAltResult {
             Self::ErrorInModule(s, err, ..) => write!(f, "Error in module {}: {}", s, err)?,
 
             Self::ErrorVariableExists(s, ..) => write!(f, "Variable is already defined: {}", s)?,
+            Self::ErrorForbiddenVariable(s, ..) => write!(f, "Forbidden variable name: {}", s)?,
             Self::ErrorVariableNotFound(s, ..) => write!(f, "Variable not found: {}", s)?,
             Self::ErrorPropertyNotFound(s, ..) => write!(f, "Property not found: {}", s)?,
             Self::ErrorFunctionNotFound(s, ..) => write!(f, "Function not found: {}", s)?,
@@ -285,6 +288,7 @@ impl EvalAltResult {
             | Self::ErrorIndexingType(..)
             | Self::ErrorFor(..)
             | Self::ErrorVariableExists(..)
+            | Self::ErrorForbiddenVariable(..)
             | Self::ErrorVariableNotFound(..)
             | Self::ErrorPropertyNotFound(..)
             | Self::ErrorModuleNotFound(..)
@@ -377,6 +381,7 @@ impl EvalAltResult {
                 map.insert("type".into(), t.into());
             }
             Self::ErrorVariableExists(v, ..)
+            | Self::ErrorForbiddenVariable(v, ..)
             | Self::ErrorVariableNotFound(v, ..)
             | Self::ErrorPropertyNotFound(v, ..)
             | Self::ErrorDataRace(v, ..)
@@ -440,6 +445,7 @@ impl EvalAltResult {
             | Self::ErrorIndexingType(.., pos)
             | Self::ErrorFor(pos)
             | Self::ErrorVariableExists(.., pos)
+            | Self::ErrorForbiddenVariable(.., pos)
             | Self::ErrorVariableNotFound(.., pos)
             | Self::ErrorPropertyNotFound(.., pos)
             | Self::ErrorModuleNotFound(.., pos)
@@ -490,6 +496,7 @@ impl EvalAltResult {
             | Self::ErrorIndexingType(.., pos)
             | Self::ErrorFor(pos)
             | Self::ErrorVariableExists(.., pos)
+            | Self::ErrorForbiddenVariable(.., pos)
             | Self::ErrorVariableNotFound(.., pos)
             | Self::ErrorPropertyNotFound(.., pos)
             | Self::ErrorModuleNotFound(.., pos)

src/types/parse_error.rs

@@ -109,6 +109,8 @@ pub enum ParseErrorType {
     PropertyExpected,
     /// Missing a variable name after the `let`, `const`, `for` or `catch` keywords.
     VariableExpected,
+    /// Forbidden variable name.  Wrapped value is the variable name.
+    ForbiddenVariable(String),
     /// An identifier is a reserved symbol.
     Reserved(String),
     /// An expression is of the wrong type.
@@ -240,6 +242,7 @@ impl fmt::Display for ParseErrorType {
             Self::WrongSwitchCaseCondition => f.write_str("This switch case cannot have a condition"),
             Self::PropertyExpected => f.write_str("Expecting name of a property"),
             Self::VariableExpected => f.write_str("Expecting name of a variable"),
+            Self::ForbiddenVariable(s) => write!(f, "Forbidden variable name: {}", s),
             Self::WrongFnDefinition => f.write_str("Function definitions must be at global level and cannot be inside a block or another function"),
             Self::FnMissingName => f.write_str("Expecting function name in function declaration"),
             Self::WrongDocComment => f.write_str("Doc-comment must be followed immediately by a function definition"),

src/types/scope.rs

@@ -595,6 +595,16 @@ impl Scope<'_> {
             .zip(self.values.iter())
             .map(|((name, ..), value)| (name.as_ref(), value.is_read_only(), value))
     }
+    /// Get a reverse iterator to entries in the [`Scope`].
+    /// Shared values are not expanded.
+    #[inline]
+    pub(crate) fn iter_rev_raw(&self) -> impl Iterator<Item = (&str, bool, &Dynamic)> {
+        self.names
+            .iter()
+            .rev()
+            .zip(self.values.iter().rev())
+            .map(|((name, ..), value)| (name.as_ref(), value.is_read_only(), value))
+    }
     /// Remove a range of entries within the [`Scope`].
     ///
     /// # Panics