Add no_inidex feature to disable arrays and indexing.

Cargo.toml

@@ -18,6 +18,12 @@ include = [
 num-traits = "*"
 
 [features]
+default = []
 debug_msgs = []
-no_stdlib = []
 unchecked = []
+no_stdlib = []
+no_index = []
+
+[profile.release]
+lto = "fat"
+codegen-units = 1

README.md

@@ -43,6 +43,7 @@ Optional features
 | `debug_msgs` | Print debug messages to stdout (using `println!`) related to function registrations and function calls.                 |
 | `no_stdlib`  | Exclude the standard library of utility functions in the build, and only include the minimum necessary functionalities. |
 | `unchecked`  | Exclude arithmetic checking in the standard library. Beware that a bad script may panic the entire system!              |
+| `no_index`   | Disable arrays and indexing features                                                                                    |
 
 Related
 -------
@@ -606,7 +607,7 @@ let booly = !true;
 Numeric functions
 -----------------
 
-The following standard functions (defined in the standard library but excluded if `no_stdlib`) operate on `i8`, `i16`, `i32`, `i64`, `f32` and `f64` only:
+The following standard functions (defined in the standard library but excluded if [`no_stdlib`](#optional-features)) operate on `i8`, `i16`, `i32`, `i64`, `f32` and `f64` only:
 
 | Function   | Description                         |
 | ---------- | ----------------------------------- |
@@ -617,7 +618,7 @@ The following standard functions (defined in the standard library but excluded i
 Floating-point functions
 ------------------------
 
-The following standard functions (defined in the standard library but excluded if `no_stdlib`) operate on `f64` only:
+The following standard functions (defined in the standard library but excluded if [`no_stdlib`](#optional-features)) operate on `f64` only:
 
 | Category         | Functions                                                    |
 | ---------------- | ------------------------------------------------------------ |
@@ -645,7 +646,7 @@ let age = 42;
 let record = full_name + ": age " + age;
 record == "Bob C. Davis: age 42";
 
-// Strings can be indexed to get a character
+// Strings can be indexed to get a character (disabled with the 'no_index' feature)
 let c = record[4];
 c == 'C';
 
@@ -669,7 +670,7 @@ record[4] = '\x58'; // 0x58 = 'X'
 record == "Bob X. Davis: age 42 ❤\n";
 ```
 
-The following standard functions (defined in the standard library but excluded if `no_stdlib`) operate on strings:
+The following standard functions (defined in the standard library but excluded if [`no_stdlib`](#optional-features)) operate on strings:
 
 | Function   | Description                                                              |
 | ---------- | ------------------------------------------------------------------------ |
@@ -716,7 +717,7 @@ Arrays
 
 You can create arrays of values, and then access them with numeric indices.
 
-The following functions (defined in the standard library but excluded if `no_stdlib`) operate on arrays:
+The following functions (defined in the standard library but excluded if [`no_stdlib`](#optional-features)) operate on arrays:
 
 | Function   | Description                                                                           |
 | ---------- | ------------------------------------------------------------------------------------- |
@@ -788,6 +789,8 @@ engine.register_fn("push",
 
 The type of a Rhai array is `rhai::Array`. `type_of()` returns `"array"`.
 
+Arrays are disabled via the [`no_index`](#optional-features) feature.
+
 Comparison operators
 --------------------
 

src/api.rs

@@ -104,8 +104,7 @@ impl<'e> Engine<'e> {
         parse(&mut tokens.peekable(), self.optimize)
     }
 
-    /// Compile a file into an AST.
+    fn read_file(filename: &str) -> Result<String, EvalAltResult> {
-    pub fn compile_file(&self, filename: &str) -> Result<AST, EvalAltResult> {
         let mut f = File::open(filename)
             .map_err(|err| EvalAltResult::ErrorReadingScriptFile(filename.into(), err))?;
 
@@ -113,19 +112,18 @@ impl<'e> Engine<'e> {
 
         f.read_to_string(&mut contents)
             .map_err(|err| EvalAltResult::ErrorReadingScriptFile(filename.into(), err))
-            .and_then(|_| self.compile(&contents).map_err(EvalAltResult::ErrorParsing))
+            .map(|_| contents)
+    }
+
+    /// Compile a file into an AST.
+    pub fn compile_file(&self, filename: &str) -> Result<AST, EvalAltResult> {
+        Self::read_file(filename)
+            .and_then(|contents| self.compile(&contents).map_err(|err| err.into()))
     }
 
     /// Evaluate a file.
     pub fn eval_file<T: Any + Clone>(&mut self, filename: &str) -> Result<T, EvalAltResult> {
-        let mut f = File::open(filename)
+        Self::read_file(filename).and_then(|contents| self.eval::<T>(&contents))
-            .map_err(|err| EvalAltResult::ErrorReadingScriptFile(filename.into(), err))?;
-
-        let mut contents = String::new();
-
-        f.read_to_string(&mut contents)
-            .map_err(|err| EvalAltResult::ErrorReadingScriptFile(filename.into(), err))
-            .and_then(|_| self.eval::<T>(&contents))
     }
 
     /// Evaluate a string.
@@ -164,10 +162,16 @@ impl<'e> Engine<'e> {
         retain_functions: bool,
         ast: &AST,
     ) -> Result<T, EvalAltResult> {
+        fn eval_ast_internal(
+            engine: &mut Engine,
+            scope: &mut Scope,
+            retain_functions: bool,
+            ast: &AST,
+        ) -> Result<Dynamic, EvalAltResult> {
             let AST(statements, functions) = ast;
 
             functions.iter().for_each(|f| {
-            self.script_functions.insert(
+                engine.script_functions.insert(
                     FnSpec {
                         name: f.name.clone().into(),
                         args: None,
@@ -178,13 +182,16 @@ impl<'e> Engine<'e> {
 
             let result = statements
                 .iter()
-            .try_fold(().into_dynamic(), |_, stmt| self.eval_stmt(scope, stmt));
+                .try_fold(().into_dynamic(), |_, stmt| engine.eval_stmt(scope, stmt));
 
             if !retain_functions {
-            self.clear_functions();
+                engine.clear_functions();
             }
 
-        match result {
+            result
+        }
+
+        match eval_ast_internal(self, scope, retain_functions, ast) {
             Err(EvalAltResult::Return(out, pos)) => out.downcast::<T>().map(|v| *v).map_err(|a| {
                 EvalAltResult::ErrorMismatchOutputType(
                     self.map_type_name((*a).type_name()).to_string(),
@@ -285,25 +292,14 @@ impl<'e> Engine<'e> {
         ast: &AST,
         args: A,
     ) -> Result<T, EvalAltResult> {
-        let mut arg_values = args.into_vec();
+        fn call_fn_internal(
-
+            engine: &mut Engine,
-        self.call_fn_internal(
-            name,
-            ast,
-            arg_values.iter_mut().map(|v| v.as_mut()).collect(),
-        )
-    }
-
-    pub(crate) fn call_fn_internal<T: Any + Clone>(
-        &mut self,
             name: &str,
             ast: &AST,
             args: FnCallArgs,
-    ) -> Result<T, EvalAltResult> {
+        ) -> Result<Dynamic, EvalAltResult> {
-        let pos = Default::default();
-
             ast.1.iter().for_each(|f| {
-            self.script_functions.insert(
+                engine.script_functions.insert(
                     FnSpec {
                         name: f.name.clone().into(),
                         args: None,
@@ -312,18 +308,29 @@ impl<'e> Engine<'e> {
                 );
             });
 
-        let result = self.call_fn_raw(name, args, None, pos).and_then(|b| {
+            let result = engine.call_fn_raw(name, args, None, Position::none());
+
+            engine.clear_functions();
+
+            result
+        }
+
+        let mut arg_values = args.into_vec();
+
+        call_fn_internal(
+            self,
+            name,
+            ast,
+            arg_values.iter_mut().map(|v| v.as_mut()).collect(),
+        )
+        .and_then(|b| {
             b.downcast().map(|b| *b).map_err(|a| {
                 EvalAltResult::ErrorMismatchOutputType(
                     self.map_type_name((*a).type_name()).into(),
-                    pos,
+                    Position::none(),
                 )
             })
-        });
+        })
-
-        self.clear_functions();
-
-        result
     }
 
     /// Override default action of `print` (print to stdout using `println!`)

src/builtin.rs

@@ -2,8 +2,12 @@
 //! _standard library_ of utility functions.
 
 use crate::any::Any;
-use crate::engine::{Array, Engine};
+use crate::engine::Engine;
 use crate::fn_register::RegisterFn;
+
+#[cfg(not(feature = "no_index"))]
+use crate::engine::Array;
+
 use std::{
     fmt::{Debug, Display},
     i32, i64,
@@ -15,14 +19,13 @@ use std::{
 use std::ops::{Shl, Shr};
 
 #[cfg(not(feature = "unchecked"))]
-use crate::{parser::Position, result::EvalAltResult, RegisterResultFn};
+use {
-
+    crate::{parser::Position, result::EvalAltResult, RegisterResultFn},
-#[cfg(not(feature = "unchecked"))]
+    num_traits::{
-use std::convert::TryFrom;
+        CheckedAdd, CheckedDiv, CheckedMul, CheckedNeg, CheckedRem, CheckedShl, CheckedShr,
-
+        CheckedSub,
-#[cfg(not(feature = "unchecked"))]
+    },
-use num_traits::{
+    std::convert::TryFrom,
-    CheckedAdd, CheckedDiv, CheckedMul, CheckedNeg, CheckedRem, CheckedShl, CheckedShr, CheckedSub,
 };
 
 macro_rules! reg_op {
@@ -102,6 +105,7 @@ macro_rules! reg_func2y {
 }
 
 #[cfg(not(feature = "no_stdlib"))]
+#[cfg(not(feature = "no_index"))]
 macro_rules! reg_func3 {
     ($self:expr, $x:expr, $op:expr, $v:ty, $w:ty, $r:ty, $( $y:ty ),*) => (
         $(
@@ -438,19 +442,23 @@ impl Engine<'_> {
         reg_func1!(self, "print", print, String, i8, u8, i16, u16);
         reg_func1!(self, "print", print, String, i32, i64, u32, u64);
         reg_func1!(self, "print", print, String, f32, f64, bool, char, String);
-        reg_func1!(self, "print", print_debug, String, Array);
         self.register_fn("print", || "".to_string());
         self.register_fn("print", |_: ()| "".to_string());
 
         reg_func1!(self, "debug", print_debug, String, i8, u8, i16, u16);
         reg_func1!(self, "debug", print_debug, String, i32, i64, u32, u64);
         reg_func1!(self, "debug", print_debug, String, f32, f64, bool, char);
+
+        #[cfg(not(feature = "no_index"))]
+        {
+            reg_func1!(self, "print", print_debug, String, Array);
             reg_func1!(self, "debug", print_debug, String, String, Array, ());
 
             // Register array iterator
             self.register_iterator::<Array, _>(|a| {
                 Box::new(a.downcast_ref::<Array>().unwrap().clone().into_iter())
             });
+        }
 
         // Register range function
         self.register_iterator::<Range<i64>, _>(|a| {
@@ -468,6 +476,7 @@ impl Engine<'_> {
     /// Register the built-in library.
     #[cfg(not(feature = "no_stdlib"))]
     pub(crate) fn register_stdlib(&mut self) {
+        #[cfg(not(feature = "no_index"))]
         use crate::fn_register::RegisterDynamicFn;
 
         // Advanced math functions
@@ -547,6 +556,8 @@ impl Engine<'_> {
             self.register_fn("to_int", |x: f64| x as i64);
         }
 
+        #[cfg(not(feature = "no_index"))]
+        {
             // Register array utility functions
             fn push<T: Any>(list: &mut Array, item: T) {
                 list.push(Box::new(item));
@@ -583,6 +594,7 @@ impl Engine<'_> {
                     list.truncate(len as usize);
                 }
             });
+        }
 
         // Register string concatenate functions
         fn prepend<T: Display>(x: T, y: String) -> String {
@@ -596,16 +608,20 @@ impl Engine<'_> {
             self, "+", append, String, String, i8, u8, i16, u16, i32, i64, u32, u64, f32, f64,
             bool, char
         );
-        self.register_fn("+", |x: String, y: Array| format!("{}{:?}", x, y));
         self.register_fn("+", |x: String, _: ()| format!("{}", x));
 
         reg_func2y!(
             self, "+", prepend, String, String, i8, u8, i16, u16, i32, i64, u32, u64, f32, f64,
             bool, char
         );
-        self.register_fn("+", |x: Array, y: String| format!("{:?}{}", x, y));
         self.register_fn("+", |_: (), y: String| format!("{}", y));
 
+        #[cfg(not(feature = "no_index"))]
+        {
+            self.register_fn("+", |x: String, y: Array| format!("{}{:?}", x, y));
+            self.register_fn("+", |x: Array, y: String| format!("{:?}{}", x, y));
+        }
+
         // Register string utility functions
         self.register_fn("len", |s: &mut String| s.chars().count() as i64);
         self.register_fn("contains", |s: &mut String, ch: char| s.contains(ch));

src/engine.rs

@@ -14,6 +14,7 @@ use std::{
 };
 
 /// An dynamic array of `Dynamic` values.
+#[cfg(not(feature = "no_index"))]
 pub type Array = Vec<Dynamic>;
 
 pub type FnCallArgs<'a> = Vec<&'a mut Variant>;
@@ -29,6 +30,7 @@ pub(crate) const FUNC_GETTER: &'static str = "get$";
 pub(crate) const FUNC_SETTER: &'static str = "set$";
 
 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
+#[cfg(not(feature = "no_index"))]
 enum IndexSourceType {
     Array,
     String,
@@ -82,8 +84,9 @@ impl Engine<'_> {
         // User-friendly names for built-in types
         let type_names = [
             (type_name::<String>(), "string"),
-            (type_name::<Array>(), "array"),
             (type_name::<Dynamic>(), "dynamic"),
+            #[cfg(not(feature = "no_index"))]
+            (type_name::<Array>(), "array"),
         ]
         .iter()
         .map(|(k, v)| (k.to_string(), v.to_string()))
@@ -251,7 +254,7 @@ impl Engine<'_> {
         match dot_rhs {
             // xxx.fn_name(args)
             Expr::FunctionCall(fn_name, args, def_val, pos) => {
-                let mut args: Array = args
+                let mut args = args
                     .iter()
                     .map(|arg| self.eval_expr(scope, arg))
                     .collect::<Result<Vec<_>, _>>()?;
@@ -271,6 +274,7 @@ impl Engine<'_> {
             }
 
             // xxx.idx_lhs[idx_expr]
+            #[cfg(not(feature = "no_index"))]
             Expr::Index(idx_lhs, idx_expr, idx_pos) => {
                 let (expr, _) = match idx_lhs.as_ref() {
                     // xxx.id[idx_expr]
@@ -309,6 +313,7 @@ impl Engine<'_> {
                         .and_then(|mut v| self.get_dot_val_helper(scope, v.as_mut(), rhs))
                 }
                 // xxx.idx_lhs[idx_expr].rhs
+                #[cfg(not(feature = "no_index"))]
                 Expr::Index(idx_lhs, idx_expr, idx_pos) => {
                     let (expr, _) = match idx_lhs.as_ref() {
                         // xxx.id[idx_expr].rhs
@@ -371,6 +376,7 @@ impl Engine<'_> {
             }
 
             // idx_lhs[idx_expr].???
+            #[cfg(not(feature = "no_index"))]
             Expr::Index(idx_lhs, idx_expr, idx_pos) => {
                 let (src_type, src, idx, mut target) =
                     self.eval_index_expr(scope, idx_lhs, idx_expr, *idx_pos)?;
@@ -414,6 +420,7 @@ impl Engine<'_> {
     }
 
     /// Evaluate the value of an index (must evaluate to i64)
+    #[cfg(not(feature = "no_index"))]
     fn eval_index_value(
         &mut self,
         scope: &mut Scope,
@@ -426,6 +433,7 @@ impl Engine<'_> {
     }
 
     /// Get the value at the indexed position of a base type
+    #[cfg(not(feature = "no_index"))]
     fn get_indexed_value(
         &self,
         val: Dynamic,
@@ -473,6 +481,7 @@ impl Engine<'_> {
     }
 
     /// Evaluate an index expression
+    #[cfg(not(feature = "no_index"))]
     fn eval_index_expr<'a>(
         &mut self,
         scope: &mut Scope,
@@ -505,6 +514,7 @@ impl Engine<'_> {
     }
 
     /// Replace a character at an index position in a mutable string
+    #[cfg(not(feature = "no_index"))]
     fn str_replace_char(s: &mut String, idx: usize, new_ch: char) {
         let mut chars: Vec<char> = s.chars().collect();
         let ch = *chars.get(idx).expect("string index out of bounds");
@@ -518,6 +528,7 @@ impl Engine<'_> {
     }
 
     /// Update the value at an index position in a variable inside the scope
+    #[cfg(not(feature = "no_index"))]
     fn update_indexed_var_in_scope(
         src_type: IndexSourceType,
         scope: &mut Scope,
@@ -550,6 +561,7 @@ impl Engine<'_> {
     }
 
     /// Update the value at an index position
+    #[cfg(not(feature = "no_index"))]
     fn update_indexed_value(
         mut target: Dynamic,
         idx: usize,
@@ -593,6 +605,7 @@ impl Engine<'_> {
 
             // xxx.lhs[idx_expr]
             // TODO - Allow chaining of indexing!
+            #[cfg(not(feature = "no_index"))]
             Expr::Index(lhs, idx_expr, idx_pos) => match lhs.as_ref() {
                 // xxx.id[idx_expr]
                 Expr::Identifier(id, pos) => {
@@ -636,6 +649,7 @@ impl Engine<'_> {
 
                 // xxx.lhs[idx_expr].rhs
                 // TODO - Allow chaining of indexing!
+                #[cfg(not(feature = "no_index"))]
                 Expr::Index(lhs, idx_expr, idx_pos) => match lhs.as_ref() {
                     // xxx.id[idx_expr].rhs
                     Expr::Identifier(id, pos) => {
@@ -720,6 +734,7 @@ impl Engine<'_> {
 
             // lhs[idx_expr].???
             // TODO - Allow chaining of indexing!
+            #[cfg(not(feature = "no_index"))]
             Expr::Index(lhs, idx_expr, idx_pos) => {
                 let (src_type, src, idx, mut target) =
                     self.eval_index_expr(scope, lhs, idx_expr, *idx_pos)?;
@@ -762,6 +777,7 @@ impl Engine<'_> {
             }
 
             // lhs[idx_expr]
+            #[cfg(not(feature = "no_index"))]
             Expr::Index(lhs, idx_expr, idx_pos) => self
                 .eval_index_expr(scope, lhs, idx_expr, *idx_pos)
                 .map(|(_, _, _, x)| x),
@@ -785,6 +801,7 @@ impl Engine<'_> {
                     }
 
                     // idx_lhs[idx_expr] = rhs
+                    #[cfg(not(feature = "no_index"))]
                     Expr::Index(idx_lhs, idx_expr, idx_pos) => {
                         let (src_type, src, idx, _) =
                             self.eval_index_expr(scope, idx_lhs, idx_expr, *idx_pos)?;
@@ -818,6 +835,7 @@ impl Engine<'_> {
 
             Expr::Dot(lhs, rhs, _) => self.get_dot_val(scope, lhs, rhs),
 
+            #[cfg(not(feature = "no_index"))]
             Expr::Array(contents, _) => {
                 let mut arr = Vec::new();
 
@@ -836,7 +854,7 @@ impl Engine<'_> {
                 let mut args = args
                     .iter()
                     .map(|expr| self.eval_expr(scope, expr))
-                    .collect::<Result<Array, _>>()?;
+                    .collect::<Result<Vec<Dynamic>, _>>()?;
 
                 self.call_fn_raw(
                     fn_name,

src/lib.rs

@@ -75,9 +75,12 @@ mod scope;
 
 pub use any::{Any, AnyExt, Dynamic, Variant};
 pub use call::FuncArgs;
-pub use engine::{Array, Engine};
+pub use engine::Engine;
 pub use error::{ParseError, ParseErrorType};
 pub use fn_register::{RegisterDynamicFn, RegisterFn, RegisterResultFn};
 pub use parser::{Position, AST};
 pub use result::EvalAltResult;
 pub use scope::Scope;
+
+#[cfg(not(feature = "no_index"))]
+pub use engine::Array;

src/optimize.rs

@@ -139,11 +139,24 @@ fn optimize_expr(expr: Expr, changed: &mut bool) -> Expr {
             Box::new(optimize_expr(*rhs, changed)),
             pos,
         ),
-        Expr::Index(lhs, rhs, pos) => Expr::Index(
+        #[cfg(not(feature = "no_index"))]
-            Box::new(optimize_expr(*lhs, changed)),
+        Expr::Index(lhs, rhs, pos) => match (*lhs, *rhs) {
-            Box::new(optimize_expr(*rhs, changed)),
+            (Expr::Array(mut items, _), Expr::IntegerConstant(i, _))
+                if i >= 0
+                    && (i as usize) < items.len()
+                    && !items.iter().any(|x| x.is_constant()) =>
+            {
+                // Array where everything is a constant - promote the item
+                *changed = true;
+                items.remove(i as usize)
+            }
+            (lhs, rhs) => Expr::Index(
+                Box::new(optimize_expr(lhs, changed)),
+                Box::new(optimize_expr(rhs, changed)),
                 pos,
             ),
+        },
+        #[cfg(not(feature = "no_index"))]
         Expr::Array(items, pos) => {
             let original_len = items.len();
 

src/parser.rs

@@ -167,7 +167,9 @@ pub enum Expr {
     FunctionCall(String, Vec<Expr>, Option<Dynamic>, Position),
     Assignment(Box<Expr>, Box<Expr>, Position),
     Dot(Box<Expr>, Box<Expr>, Position),
+    #[cfg(not(feature = "no_index"))]
     Index(Box<Expr>, Box<Expr>, Position),
+    #[cfg(not(feature = "no_index"))]
     Array(Vec<Expr>, Position),
     And(Box<Expr>, Box<Expr>),
     Or(Box<Expr>, Box<Expr>),
@@ -186,16 +188,19 @@ impl Expr {
             | Expr::StringConstant(_, pos)
             | Expr::FunctionCall(_, _, _, pos)
             | Expr::Stmt(_, pos)
-            | Expr::Array(_, pos)
             | Expr::True(pos)
             | Expr::False(pos)
             | Expr::Unit(pos) => *pos,
 
-            Expr::Index(e, _, _)
+            Expr::Assignment(e, _, _) | Expr::Dot(e, _, _) | Expr::And(e, _) | Expr::Or(e, _) => {
-            | Expr::Assignment(e, _, _)
+                e.position()
-            | Expr::Dot(e, _, _)
+            }
-            | Expr::And(e, _)
+
-            | Expr::Or(e, _) => e.position(),
+            #[cfg(not(feature = "no_index"))]
+            Expr::Index(e, _, _) => e.position(),
+
+            #[cfg(not(feature = "no_index"))]
+            Expr::Array(_, pos) => *pos,
         }
     }
 
@@ -1166,6 +1171,7 @@ fn parse_call_expr<'a>(
     }
 }
 
+#[cfg(not(feature = "no_index"))]
 fn parse_index_expr<'a>(
     lhs: Box<Expr>,
     input: &mut Peekable<TokenIterator<'a>>,
@@ -1260,6 +1266,7 @@ fn parse_ident_expr<'a>(
             input.next();
             parse_call_expr(id, input, begin)
         }
+        #[cfg(not(feature = "no_index"))]
         Some(&(Token::LeftBracket, pos)) => {
             input.next();
             parse_index_expr(Box::new(Expr::Identifier(id, begin)), input, pos)
@@ -1269,6 +1276,7 @@ fn parse_ident_expr<'a>(
     }
 }
 
+#[cfg(not(feature = "no_index"))]
 fn parse_array_expr<'a>(
     input: &mut Peekable<TokenIterator<'a>>,
     begin: Position,
@@ -1320,26 +1328,28 @@ fn parse_primary<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Expr, Pa
 
     let token = input.next();
 
-    let mut follow_on = false;
+    let mut can_be_indexed = false;
 
+    #[allow(unused_mut)]
     let mut root_expr = match token {
         Some((Token::IntegerConstant(x), pos)) => Ok(Expr::IntegerConstant(x, pos)),
         Some((Token::FloatConstant(x), pos)) => Ok(Expr::FloatConstant(x, pos)),
         Some((Token::CharConstant(c), pos)) => Ok(Expr::CharConstant(c, pos)),
         Some((Token::StringConst(s), pos)) => {
-            follow_on = true;
+            can_be_indexed = true;
             Ok(Expr::StringConstant(s, pos))
         }
         Some((Token::Identifier(s), pos)) => {
-            follow_on = true;
+            can_be_indexed = true;
             parse_ident_expr(s, input, pos)
         }
         Some((Token::LeftParen, pos)) => {
-            follow_on = true;
+            can_be_indexed = true;
             parse_paren_expr(input, pos)
         }
+        #[cfg(not(feature = "no_index"))]
         Some((Token::LeftBracket, pos)) => {
-            follow_on = true;
+            can_be_indexed = true;
             parse_array_expr(input, pos)
         }
         Some((Token::True, pos)) => Ok(Expr::True(pos)),
@@ -1354,15 +1364,14 @@ fn parse_primary<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Expr, Pa
         None => Err(ParseError::new(PERR::InputPastEndOfFile, Position::eof())),
     }?;
 
-    if !follow_on {
+    if can_be_indexed {
-        return Ok(root_expr);
-    }
-
         // Tail processing all possible indexing
+        #[cfg(not(feature = "no_index"))]
         while let Some(&(Token::LeftBracket, pos)) = input.peek() {
             input.next();
             root_expr = parse_index_expr(Box::new(root_expr), input, pos)?;
         }
+    }
 
     Ok(root_expr)
 }
@@ -1408,6 +1417,7 @@ fn parse_assignment(lhs: Expr, rhs: Expr, pos: Position) -> Result<Expr, ParseEr
         match expr {
             Expr::Identifier(_, pos) => (true, *pos),
 
+            #[cfg(not(feature = "no_index"))]
             Expr::Index(idx_lhs, _, _) => match idx_lhs.as_ref() {
                 Expr::Identifier(_, _) => (true, idx_lhs.position()),
                 _ => (false, idx_lhs.position()),
@@ -1415,10 +1425,13 @@ fn parse_assignment(lhs: Expr, rhs: Expr, pos: Position) -> Result<Expr, ParseEr
 
             Expr::Dot(dot_lhs, dot_rhs, _) => match dot_lhs.as_ref() {
                 Expr::Identifier(_, _) => valid_assignment_chain(dot_rhs),
+
+                #[cfg(not(feature = "no_index"))]
                 Expr::Index(idx_lhs, _, _) => match idx_lhs.as_ref() {
                     Expr::Identifier(_, _) => valid_assignment_chain(dot_rhs),
                     _ => (false, idx_lhs.position()),
                 },
+
                 _ => (false, dot_lhs.position()),
             },
 

src/result.rs

@@ -173,6 +173,12 @@ impl From<ParseError> for EvalAltResult {
     }
 }
 
+impl<T: AsRef<str>> From<T> for EvalAltResult {
+    fn from(err: T) -> Self {
+        Self::ErrorRuntime(err.as_ref().to_string(), Position::none())
+    }
+}
+
 impl EvalAltResult {
     pub fn position(&self) -> Position {
         match self {
@@ -225,9 +231,3 @@ impl EvalAltResult {
         }
     }
 }
-
-impl<T: AsRef<str>> From<T> for EvalAltResult {
-    fn from(err: T) -> Self {
-        Self::ErrorRuntime(err.as_ref().to_string(), Position::none())
-    }
-}

src/scope.rs

@@ -93,6 +93,7 @@ impl<'a> Scope<'a> {
     }
 
     /// Get a mutable reference to a variable in the Scope and downcast it to a specific type
+    #[cfg(not(feature = "no_index"))]
     pub(crate) fn get_mut_by_type<T: Any + Clone>(&mut self, key: &str, index: usize) -> &mut T {
         self.get_mut(key, index)
             .downcast_mut::<T>()