Add custom syntax.

README.md

@@ -34,7 +34,8 @@ Features
 * Rugged - protected against malicious attacks (such as [stack-overflow](https://schungx.github.io/rhai/safety/max-call-stack.html), [over-sized data](https://schungx.github.io/rhai/safety/max-string-size.html), and [runaway scripts](https://schungx.github.io/rhai/safety/max-operations.html) etc.) that may come from untrusted third-party user-land scripts.
 * Track script evaluation [progress](https://schungx.github.io/rhai/safety/progress.html) and manually terminate a script run.
 * [Function overloading](https://schungx.github.io/rhai/language/overload.html).
-* [Operator overloading](https://schungx.github.io/rhai/rust/operators.html) and [custom operators](https://schungx.github.io/rhai/engine/custom-op.html).
+* [Operator overloading](https://schungx.github.io/rhai/rust/operators.html).
+* Support for use as a [DSL](https://schungx.github.io/rhai/engine/dsl.html) - [disabling keywords/operators](https://schungx.github.io/rhai/engine/disable.html), [custom operators](https://schungx.github.io/rhai/engine/custom-op.html).
 * Dynamic dispatch via [function pointers](https://schungx.github.io/rhai/language/fn-ptr.html).
 * Some support for [object-oriented programming (OOP)](https://schungx.github.io/rhai/language/oop.html).
 * Organize code base with dynamically-loadable [modules](https://schungx.github.io/rhai/language/modules.html).

RELEASES.md

@@ -31,6 +31,7 @@ New features
 * The boolean `^` (XOR) operator is added.
 * `FnPtr` is exposed as the function pointer type.
 * `rhai::module_resolvers::ModuleResolversCollection` added to try a list of module resolvers.
+* It is now possible to mutate the first argument of a module-qualified function call when the argument is a simple variable (but not a module constant).
 
 
 Version 0.16.1

src/engine.rs

@@ -11,6 +11,7 @@ use crate::parser::{Expr, FnAccess, ImmutableString, ReturnType, ScriptFnDef, St
 use crate::r#unsafe::unsafe_cast_var_name_to_lifetime;
 use crate::result::EvalAltResult;
 use crate::scope::{EntryType as ScopeEntryType, Scope};
+use crate::syntax::CustomSyntax;
 use crate::token::Position;
 use crate::utils::StaticVec;
 
@@ -82,8 +83,12 @@ pub const KEYWORD_THIS: &str = "this";
 pub const FN_TO_STRING: &str = "to_string";
 pub const FN_GET: &str = "get$";
 pub const FN_SET: &str = "set$";
-pub const FN_IDX_GET: &str = "$index$get$";
+pub const FN_IDX_GET: &str = "index$get$";
-pub const FN_IDX_SET: &str = "$index$set$";
+pub const FN_IDX_SET: &str = "index$set$";
+pub const MARKER_EXPR: &str = "$expr$";
+pub const MARKER_STMT: &str = "$stmt$";
+pub const MARKER_BLOCK: &str = "$block$";
+pub const MARKER_IDENT: &str = "$ident$";
 
 /// A type specifying the method of chaining.
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
@@ -273,6 +278,8 @@ pub struct Engine {
     pub(crate) disabled_symbols: Option<HashSet<String>>,
     /// A hashset containing custom keywords and precedence to recognize.
     pub(crate) custom_keywords: Option<HashMap<String, u8>>,
+    /// Custom syntax.
+    pub(crate) custom_syntax: Option<HashMap<String, CustomSyntax>>,
 
     /// Callback closure for implementing the `print` command.
     pub(crate) print: Callback<str, ()>,
@@ -322,6 +329,7 @@ impl Default for Engine {
             type_names: None,
             disabled_symbols: None,
             custom_keywords: None,
+            custom_syntax: None,
 
             // default print/debug implementations
             print: Box::new(default_print),
@@ -554,6 +562,7 @@ impl Engine {
             type_names: None,
             disabled_symbols: None,
             custom_keywords: None,
+            custom_syntax: None,
 
             print: Box::new(|_| {}),
             debug: Box::new(|_| {}),
@@ -1595,6 +1604,26 @@ impl Engine {
         }
     }
 
+    /// Evaluate an expression inside an AST.
+    ///
+    /// ## WARNING - Low Level API
+    ///
+    /// This function is very low level.  It evaluates an expression from an AST.
+    #[cfg(feature = "internals")]
+    #[deprecated(note = "this method is volatile and may change")]
+    pub fn eval_expr_from_ast(
+        &self,
+        scope: &mut Scope,
+        mods: &mut Imports,
+        state: &mut State,
+        lib: &Module,
+        this_ptr: &mut Option<&mut Dynamic>,
+        expr: &Expr,
+        level: usize,
+    ) -> Result<Dynamic, Box<EvalAltResult>> {
+        self.eval_expr(scope, mods, state, lib, this_ptr, expr, level)
+    }
+
     /// Evaluate an expression
     fn eval_expr(
         &self,
@@ -2026,6 +2055,12 @@ impl Engine {
             Expr::False(_) => Ok(false.into()),
             Expr::Unit(_) => Ok(().into()),
 
+            Expr::Custom(x) => {
+                let func = (x.0).1.as_ref();
+                let exprs = (x.0).0.as_ref();
+                func(self, scope, mods, state, lib, this_ptr, exprs, level)
+            }
+
             _ => unreachable!(),
         };
 

src/lib.rs

@@ -91,6 +91,7 @@ mod scope;
 mod serde;
 mod settings;
 mod stdlib;
+mod syntax;
 mod token;
 mod r#unsafe;
 mod utils;
@@ -153,13 +154,21 @@ pub use optimize::OptimizationLevel;
 
 // Expose internal data structures.
 
+#[cfg(feature = "internals")]
+#[deprecated(note = "this type is volatile and may change")]
+pub use error::LexError;
+
 #[cfg(feature = "internals")]
 #[deprecated(note = "this type is volatile and may change")]
 pub use token::{get_next_token, parse_string_literal, InputStream, Token, TokenizeState};
 
 #[cfg(feature = "internals")]
 #[deprecated(note = "this type is volatile and may change")]
-pub use parser::{Expr, ReturnType, ScriptFnDef, Stmt};
+pub use parser::{CustomExpr, Expr, ReturnType, ScriptFnDef, Stmt};
+
+#[cfg(feature = "internals")]
+#[deprecated(note = "this type is volatile and may change")]
+pub use engine::{Imports, State as EvalState};
 
 #[cfg(feature = "internals")]
 #[deprecated(note = "this type is volatile and may change")]

src/optimize.rs

@@ -2,7 +2,7 @@ use crate::any::Dynamic;
 use crate::calc_fn_hash;
 use crate::engine::{Engine, Imports, KEYWORD_DEBUG, KEYWORD_EVAL, KEYWORD_PRINT, KEYWORD_TYPE_OF};
 use crate::module::Module;
-use crate::parser::{map_dynamic_to_expr, Expr, ReturnType, ScriptFnDef, Stmt, AST};
+use crate::parser::{map_dynamic_to_expr, CustomExpr, Expr, ReturnType, ScriptFnDef, Stmt, AST};
 use crate::scope::{Entry as ScopeEntry, EntryType as ScopeEntryType, Scope};
 use crate::utils::StaticVec;
 
@@ -598,6 +598,14 @@ fn optimize_expr(expr: Expr, state: &mut State) -> Expr {
             state.find_constant(&name).expect("should find constant in scope!").clone().set_position(pos)
         }
 
+        // Custom syntax
+        Expr::Custom(x) => Expr::Custom(Box::new((
+            CustomExpr(
+                (x.0).0.into_iter().map(|expr| optimize_expr(expr, state)).collect(),
+                (x.0).1),
+            x.1
+        ))),
+
         // All other expressions - skip
         expr => expr,
     }

src/parser.rs

@@ -2,11 +2,16 @@
 
 use crate::any::{Dynamic, Union};
 use crate::calc_fn_hash;
-use crate::engine::{make_getter, make_setter, Engine, KEYWORD_THIS};
+use crate::engine::{
+    make_getter, make_setter, Engine, KEYWORD_THIS, MARKER_BLOCK, MARKER_EXPR, MARKER_IDENT,
+    MARKER_STMT,
+};
 use crate::error::{LexError, ParseError, ParseErrorType};
+use crate::fn_native::Shared;
 use crate::module::{Module, ModuleRef};
 use crate::optimize::{optimize_into_ast, OptimizationLevel};
 use crate::scope::{EntryType as ScopeEntryType, Scope};
+use crate::syntax::FnCustomSyntaxEval;
 use crate::token::{Position, Token, TokenStream};
 use crate::utils::{StaticVec, StraightHasherBuilder};
 
@@ -568,6 +573,15 @@ impl Stmt {
     }
 }
 
+#[derive(Clone)]
+pub struct CustomExpr(pub StaticVec<Expr>, pub Shared<FnCustomSyntaxEval>);
+
+impl fmt::Debug for CustomExpr {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.0, f)
+    }
+}
+
 /// An expression.
 ///
 /// Each variant is at most one pointer in size (for speed),
@@ -632,6 +646,8 @@ pub enum Expr {
     False(Position),
     /// ()
     Unit(Position),
+    /// Custom syntax
+    Custom(Box<(CustomExpr, Position)>),
 }
 
 impl Default for Expr {
@@ -726,6 +742,8 @@ impl Expr {
             Self::True(pos) | Self::False(pos) | Self::Unit(pos) => *pos,
 
             Self::Dot(x) | Self::Index(x) => x.0.position(),
+
+            Self::Custom(x) => x.1,
         }
     }
 
@@ -758,6 +776,7 @@ impl Expr {
             Self::Assignment(x) => x.3 = new_pos,
             Self::Dot(x) => x.2 = new_pos,
             Self::Index(x) => x.2 = new_pos,
+            Self::Custom(x) => x.1 = new_pos,
         }
 
         self
@@ -861,6 +880,8 @@ impl Expr {
                 Token::LeftParen => true,
                 _ => false,
             },
+
+            Self::Custom(_) => false,
         }
     }
 
@@ -2024,6 +2045,85 @@ fn parse_expr(
     settings.pos = input.peek().unwrap().1;
     settings.ensure_level_within_max_limit(state.max_expr_depth)?;
 
+    // Check if it is a custom syntax.
+    if let Some(ref custom) = state.engine.custom_syntax {
+        let (token, pos) = input.peek().unwrap();
+        let token_pos = *pos;
+
+        match token {
+            Token::Custom(key) if custom.contains_key(key) => {
+                let custom = custom.get_key_value(key).unwrap();
+                let (key, syntax) = custom;
+
+                input.next().unwrap();
+
+                let mut exprs: StaticVec<Expr> = Default::default();
+
+                // Adjust the variables stack
+                match syntax.scope_delta {
+                    delta if delta > 0 => {
+                        state.stack.push(("".to_string(), ScopeEntryType::Normal))
+                    }
+                    delta if delta < 0 && state.stack.len() <= delta.abs() as usize => {
+                        state.stack.clear()
+                    }
+                    delta if delta < 0 => state
+                        .stack
+                        .truncate(state.stack.len() - delta.abs() as usize),
+                    _ => (),
+                }
+
+                for segment in syntax.segments.iter() {
+                    settings.pos = input.peek().unwrap().1;
+                    let settings = settings.level_up();
+
+                    match segment.as_str() {
+                        MARKER_IDENT => match input.next().unwrap() {
+                            (Token::Identifier(s), pos) => {
+                                exprs.push(Expr::Variable(Box::new(((s, pos), None, 0, None))));
+                            }
+                            (_, pos) => return Err(PERR::VariableExpected.into_err(pos)),
+                        },
+                        MARKER_EXPR => exprs.push(parse_expr(input, state, lib, settings)?),
+                        MARKER_STMT => {
+                            let stmt = parse_stmt(input, state, lib, settings)?
+                                .unwrap_or_else(|| Stmt::Noop(settings.pos));
+                            let pos = stmt.position();
+                            exprs.push(Expr::Stmt(Box::new((stmt, pos))))
+                        }
+                        MARKER_BLOCK => {
+                            let stmt = parse_block(input, state, lib, settings)?;
+                            let pos = stmt.position();
+                            exprs.push(Expr::Stmt(Box::new((stmt, pos))))
+                        }
+                        s => match input.peek().unwrap() {
+                            (Token::Custom(custom), _) if custom == s => {
+                                input.next().unwrap();
+                            }
+                            (t, _) if t.syntax().as_ref() == s => {
+                                input.next().unwrap();
+                            }
+                            (_, pos) => {
+                                return Err(PERR::MissingToken(
+                                    s.to_string(),
+                                    format!("for '{}' expression", key),
+                                )
+                                .into_err(*pos))
+                            }
+                        },
+                    }
+                }
+
+                return Ok(Expr::Custom(Box::new((
+                    CustomExpr(exprs, syntax.func.clone()),
+                    token_pos,
+                ))));
+            }
+            _ => (),
+        }
+    }
+
+    // Parse expression normally.
     let lhs = parse_unary(input, state, lib, settings.level_up())?;
     parse_binary_op(input, state, lib, 1, lhs, settings.level_up())
 }
@@ -2297,7 +2397,7 @@ fn parse_import(
 fn parse_export(
     input: &mut TokenStream,
     state: &mut ParseState,
-    lib: &mut FunctionsLib,
+    _lib: &mut FunctionsLib,
     mut settings: ParseSettings,
 ) -> Result<Stmt, ParseError> {
     settings.pos = eat_token(input, Token::Export);

src/syntax.rs

@@ -0,0 +1,132 @@
+use crate::any::Dynamic;
+use crate::engine::{Engine, Imports, State, MARKER_BLOCK, MARKER_EXPR, MARKER_IDENT, MARKER_STMT};
+use crate::error::LexError;
+use crate::fn_native::{SendSync, Shared};
+use crate::module::Module;
+use crate::parser::Expr;
+use crate::result::EvalAltResult;
+use crate::scope::Scope;
+use crate::token::{is_valid_identifier, Token};
+use crate::utils::StaticVec;
+
+use crate::stdlib::{
+    fmt,
+    rc::Rc,
+    string::{String, ToString},
+    sync::Arc,
+};
+
+/// A general function trail object.
+#[cfg(not(feature = "sync"))]
+pub type FnCustomSyntaxEval = dyn Fn(
+    &Engine,
+    &mut Scope,
+    &mut Imports,
+    &mut State,
+    &Module,
+    &mut Option<&mut Dynamic>,
+    &[Expr],
+    usize,
+) -> Result<Dynamic, Box<EvalAltResult>>;
+/// A general function trail object.
+#[cfg(feature = "sync")]
+pub type FnCustomSyntaxEval = dyn Fn(
+        &Engine,
+        &mut Scope,
+        &mut Imports,
+        &mut State,
+        &Module,
+        &mut Option<&mut Dynamic>,
+        &[Expr],
+        usize,
+    ) -> Result<Dynamic, Box<EvalAltResult>>
+    + Send
+    + Sync;
+
+#[derive(Clone)]
+pub struct CustomSyntax {
+    pub segments: StaticVec<String>,
+    pub func: Shared<FnCustomSyntaxEval>,
+    pub scope_delta: isize,
+}
+
+impl fmt::Debug for CustomSyntax {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.segments, f)
+    }
+}
+
+impl Engine {
+    pub fn add_custom_syntax<S: AsRef<str> + ToString>(
+        &mut self,
+        value: &[S],
+        scope_delta: isize,
+        func: impl Fn(
+                &Engine,
+                &mut Scope,
+                &mut Imports,
+                &mut State,
+                &Module,
+                &mut Option<&mut Dynamic>,
+                &[Expr],
+                usize,
+            ) -> Result<Dynamic, Box<EvalAltResult>>
+            + SendSync
+            + 'static,
+    ) -> Result<(), Box<LexError>> {
+        if value.is_empty() {
+            return Err(Box::new(LexError::ImproperSymbol("".to_string())));
+        }
+
+        let mut segments: StaticVec<_> = Default::default();
+
+        for s in value {
+            let seg = match s.as_ref() {
+                // Markers not in first position
+                MARKER_EXPR | MARKER_STMT | MARKER_BLOCK | MARKER_IDENT if !segments.is_empty() => {
+                    s.to_string()
+                }
+                // Standard symbols not in first position
+                s if !segments.is_empty() && Token::lookup_from_syntax(s).is_some() => s.into(),
+                // Custom keyword
+                s if is_valid_identifier(s.chars()) => {
+                    if self.custom_keywords.is_none() {
+                        self.custom_keywords = Some(Default::default());
+                    }
+
+                    if !self.custom_keywords.as_ref().unwrap().contains_key(s) {
+                        self.custom_keywords.as_mut().unwrap().insert(s.into(), 0);
+                    }
+
+                    s.into()
+                }
+                // Anything else is an error
+                _ => return Err(Box::new(LexError::ImproperSymbol(s.to_string()))),
+            };
+
+            segments.push(seg);
+        }
+
+        let key = segments.remove(0);
+
+        let syntax = CustomSyntax {
+            segments,
+            #[cfg(not(feature = "sync"))]
+            func: Rc::new(func),
+            #[cfg(feature = "sync")]
+            func: Arc::new(func),
+            scope_delta,
+        };
+
+        if self.custom_syntax.is_none() {
+            self.custom_syntax = Some(Default::default());
+        }
+
+        self.custom_syntax
+            .as_mut()
+            .unwrap()
+            .insert(key, syntax.into());
+
+        Ok(())
+    }
+}

src/token.rs

@@ -312,6 +312,87 @@ impl Token {
         }
     }
 
+    /// Reverse lookup a token from a piece of syntax.
+    pub fn lookup_from_syntax(syntax: &str) -> Option<Self> {
+        use Token::*;
+
+        Some(match syntax {
+            "{" => LeftBrace,
+            "}" => RightBrace,
+            "(" => LeftParen,
+            ")" => RightParen,
+            "[" => LeftBracket,
+            "]" => RightBracket,
+            "+" => Plus,
+            "-" => Minus,
+            "*" => Multiply,
+            "/" => Divide,
+            ";" => SemiColon,
+            ":" => Colon,
+            "::" => DoubleColon,
+            "," => Comma,
+            "." => Period,
+            "#{" => MapStart,
+            "=" => Equals,
+            "true" => True,
+            "false" => False,
+            "let" => Let,
+            "const" => Const,
+            "if" => If,
+            "else" => Else,
+            "while" => While,
+            "loop" => Loop,
+            "for" => For,
+            "in" => In,
+            "<" => LessThan,
+            ">" => GreaterThan,
+            "!" => Bang,
+            "<=" => LessThanEqualsTo,
+            ">=" => GreaterThanEqualsTo,
+            "==" => EqualsTo,
+            "!=" => NotEqualsTo,
+            "|" => Pipe,
+            "||" => Or,
+            "&" => Ampersand,
+            "&&" => And,
+            #[cfg(not(feature = "no_function"))]
+            "fn" => Fn,
+            "continue" => Continue,
+            "break" => Break,
+            "return" => Return,
+            "throw" => Throw,
+            "+=" => PlusAssign,
+            "-=" => MinusAssign,
+            "*=" => MultiplyAssign,
+            "/=" => DivideAssign,
+            "<<=" => LeftShiftAssign,
+            ">>=" => RightShiftAssign,
+            "&=" => AndAssign,
+            "|=" => OrAssign,
+            "^=" => XOrAssign,
+            "<<" => LeftShift,
+            ">>" => RightShift,
+            "^" => XOr,
+            "%" => Modulo,
+            "%=" => ModuloAssign,
+            "~" => PowerOf,
+            "~=" => PowerOfAssign,
+            #[cfg(not(feature = "no_function"))]
+            "private" => Private,
+            #[cfg(not(feature = "no_module"))]
+            "import" => Import,
+            #[cfg(not(feature = "no_module"))]
+            "export" => Export,
+            #[cfg(not(feature = "no_module"))]
+            "as" => As,
+            "===" | "!==" | "->" | "<-" | "=>" | ":=" | "::<" | "(*" | "*)" | "#" => {
+                Reserved(syntax.into())
+            }
+
+            _ => return None,
+        })
+    }
+
     // Is this token EOF?
     pub fn is_eof(&self) -> bool {
         use Token::*;
@@ -628,9 +709,9 @@ pub fn parse_string_literal(
 }
 
 /// Consume the next character.
-fn eat_next(stream: &mut impl InputStream, pos: &mut Position) {
+fn eat_next(stream: &mut impl InputStream, pos: &mut Position) -> Option<char> {
-    stream.get_next();
     pos.advance();
+    stream.get_next()
 }
 
 /// Scan for a block comment until the end.
@@ -858,35 +939,8 @@ fn get_next_token_inner(
                 }
 
                 return Some((
-                    match identifier.as_str() {
+                    Token::lookup_from_syntax(&identifier)
-                        "true" => Token::True,
+                        .unwrap_or_else(|| Token::Identifier(identifier)),
-                        "false" => Token::False,
-                        "let" => Token::Let,
-                        "const" => Token::Const,
-                        "if" => Token::If,
-                        "else" => Token::Else,
-                        "while" => Token::While,
-                        "loop" => Token::Loop,
-                        "continue" => Token::Continue,
-                        "break" => Token::Break,
-                        "return" => Token::Return,
-                        "throw" => Token::Throw,
-                        "for" => Token::For,
-                        "in" => Token::In,
-                        #[cfg(not(feature = "no_function"))]
-                        "private" => Token::Private,
-                        #[cfg(not(feature = "no_module"))]
-                        "import" => Token::Import,
-                        #[cfg(not(feature = "no_module"))]
-                        "export" => Token::Export,
-                        #[cfg(not(feature = "no_module"))]
-                        "as" => Token::As,
-
-                        #[cfg(not(feature = "no_function"))]
-                        "fn" => Token::Fn,
-
-                        _ => Token::Identifier(identifier),
-                    },
                     start_pos,
                 ));
             }
@@ -947,6 +1001,7 @@ fn get_next_token_inner(
                 eat_next(stream, pos);
                 return Some((Token::MapStart, start_pos));
             }
+            ('#', _) => return Some((Token::Reserved("#".into()), start_pos)),
 
             // Operators
             ('+', '=') => {
@@ -1163,40 +1218,42 @@ fn get_next_token_inner(
 }
 
 /// A type that implements the `InputStream` trait.
-/// Multiple charaacter streams are jointed together to form one single stream.
+/// Multiple character streams are jointed together to form one single stream.
 pub struct MultiInputsStream<'a> {
     /// The input character streams.
     streams: StaticVec<Peekable<Chars<'a>>>,
+    /// The current stream index.
+    index: usize,
 }
 
 impl InputStream for MultiInputsStream<'_> {
     /// Get the next character
     fn get_next(&mut self) -> Option<char> {
         loop {
-            if self.streams.is_empty() {
+            if self.index >= self.streams.len() {
                 // No more streams
                 return None;
-            } else if let Some(ch) = self.streams[0].next() {
+            } else if let Some(ch) = self.streams[self.index].next() {
                 // Next character in current stream
                 return Some(ch);
             } else {
                 // Jump to the next stream
-                let _ = self.streams.remove(0);
+                self.index += 1;
             }
         }
     }
     /// Peek the next character
     fn peek_next(&mut self) -> Option<char> {
         loop {
-            if self.streams.is_empty() {
+            if self.index >= self.streams.len() {
                 // No more streams
                 return None;
-            } else if let Some(ch) = self.streams[0].peek() {
+            } else if let Some(&ch) = self.streams[self.index].peek() {
                 // Next character in current stream
-                return Some(*ch);
+                return Some(ch);
             } else {
                 // Jump to the next stream
-                let _ = self.streams.remove(0);
+                self.index += 1;
             }
         }
     }
@@ -1252,7 +1309,11 @@ impl<'a> Iterator for TokenIterator<'a, '_> {
                         .to_string(),
                 ))),
                 "(*" | "*)" => Token::LexError(Box::new(LERR::ImproperSymbol(
-                    "'(* .. *)' is not a valid comment style. This is not Pascal! Should it be '/* .. */'?"
+                    "'(* .. *)' is not a valid comment format. This is not Pascal! Should it be '/* .. */'?"
+                        .to_string(),
+                ))),
+                "#" => Token::LexError(Box::new(LERR::ImproperSymbol(
+                    "'#' is not a valid symbol. Should it be '#{'?"
                         .to_string(),
                 ))),
                 token => Token::LexError(Box::new(LERR::ImproperSymbol(
@@ -1298,6 +1359,7 @@ pub fn lex<'a, 'e>(input: &'a [&'a str], engine: &'e Engine) -> TokenIterator<'a
         pos: Position::new(1, 0),
         stream: MultiInputsStream {
             streams: input.iter().map(|s| s.chars().peekable()).collect(),
+            index: 0,
         },
     }
 }

tests/maps.rs

@@ -21,7 +21,7 @@ fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
                 r#"
                     let y = #{d: 1, "e": #{a: 42, b: 88, "": "hello"}, " 123 xyz": 9};
                     y.e[""][4]
-            "#
+                "#
             )?,
             'o'
         );
@@ -47,7 +47,7 @@ fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
                 let x = #{a: 1, b: 2, c: 3};
                 let c = x.remove("c");
                 x.len() + c
-           "#
+            "#
         )?,
         5
     );
@@ -58,7 +58,7 @@ fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
                 let y = #{b: 42, d: 9};
                 x.mixin(y);
                 x.len() + x.b
-           "
+            "
         )?,
         46
     );
@@ -68,7 +68,7 @@ fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
                 let x = #{a: 1, b: 2, c: 3};
                 x += #{b: 42, d: 9};
                 x.len() + x.b
-           "
+            "
         )?,
         46
     );
@@ -79,7 +79,7 @@ fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
                     let x = #{a: 1, b: 2, c: 3};
                     let y = #{b: 42, d: 9};
                     x + y
-           "
+                "
             )?
             .len(),
         4
@@ -94,27 +94,9 @@ fn test_map_assign() -> Result<(), Box<EvalAltResult>> {
 
     let x = engine.eval::<Map>(r#"let x = #{a: 1, b: true, "c$": "hello"}; x"#)?;
 
-    assert_eq!(
+    assert_eq!(x["a"].clone().cast::<INT>(), 1);
-        x.get("a")
+    assert_eq!(x["b"].clone().cast::<bool>(), true);
-            .cloned()
+    assert_eq!(x["c$"].clone().cast::<String>(), "hello");
-            .expect("should have property a")
-            .cast::<INT>(),
-        1
-    );
-    assert_eq!(
-        x.get("b")
-            .cloned()
-            .expect("should have property b")
-            .cast::<bool>(),
-        true
-    );
-    assert_eq!(
-        x.get("c$")
-            .cloned()
-            .expect("should have property c$")
-            .cast::<String>(),
-        "hello"
-    );
 
     Ok(())
 }
@@ -125,27 +107,9 @@ fn test_map_return() -> Result<(), Box<EvalAltResult>> {
 
     let x = engine.eval::<Map>(r#"#{a: 1, b: true, "c$": "hello"}"#)?;
 
-    assert_eq!(
+    assert_eq!(x["a"].clone().cast::<INT>(), 1);
-        x.get("a")
+    assert_eq!(x["b"].clone().cast::<bool>(), true);
-            .cloned()
+    assert_eq!(x["c$"].clone().cast::<String>(), "hello");
-            .expect("should have property a")
-            .cast::<INT>(),
-        1
-    );
-    assert_eq!(
-        x.get("b")
-            .cloned()
-            .expect("should have property b")
-            .cast::<bool>(),
-        true
-    );
-    assert_eq!(
-        x.get("c$")
-            .cloned()
-            .expect("should have property c$")
-            .cast::<String>(),
-        "hello"
-    );
 
     Ok(())
 }
@@ -167,7 +131,7 @@ fn test_map_for() -> Result<(), Box<EvalAltResult>> {
                     }
 
                     s
-        "#
+                "#
             )?
             .len(),
         11
@@ -188,41 +152,11 @@ fn test_map_json() -> Result<(), Box<EvalAltResult>> {
 
     assert!(!map.contains_key("x"));
 
-    assert_eq!(
+    assert_eq!(map["a"].clone().cast::<INT>(), 1);
-        map.get("a")
+    assert_eq!(map["b"].clone().cast::<bool>(), true);
-            .cloned()
+    assert_eq!(map["c"].clone().cast::<INT>(), 42);
-            .expect("should have property a")
+    assert_eq!(map["$d e f!"].clone().cast::<String>(), "hello");
-            .cast::<INT>(),
+    assert_eq!(map["z"].clone().cast::<()>(), ());
-        1
-    );
-    assert_eq!(
-        map.get("b")
-            .cloned()
-            .expect("should have property b")
-            .cast::<bool>(),
-        true
-    );
-    assert_eq!(
-        map.get("c")
-            .cloned()
-            .expect("should have property a")
-            .cast::<INT>(),
-        42
-    );
-    assert_eq!(
-        map.get("$d e f!")
-            .cloned()
-            .expect("should have property $d e f!")
-            .cast::<String>(),
-        "hello"
-    );
-    assert_eq!(
-        map.get("z")
-            .cloned()
-            .expect("should have property z")
-            .cast::<()>(),
-        ()
-    );
 
     #[cfg(not(feature = "no_index"))]
     {
@@ -241,7 +175,7 @@ fn test_map_json() -> Result<(), Box<EvalAltResult>> {
                         }
 
                         s
-        "#
+                    "#
                 )?
                 .len(),
             11
@@ -265,7 +199,7 @@ fn test_map_oop() -> Result<(), Box<EvalAltResult>> {
 
                 obj.action(2);
                 obj.data
-        "#,
+            "#,
         )?,
         42
     );

tests/syntax.rs

@@ -0,0 +1,69 @@
+#![cfg(feature = "internals")]
+use rhai::{
+    Dynamic, Engine, EvalAltResult, EvalState, Expr, Imports, LexError, Module, Scope, INT,
+};
+
+#[test]
+fn test_custom_syntax() -> Result<(), Box<EvalAltResult>> {
+    let mut engine = Engine::new();
+
+    engine
+        .add_custom_syntax(
+            &["do", "$ident$", "$block$", "while", "$expr$"],
+            1,
+            |engine: &Engine,
+             scope: &mut Scope,
+             mods: &mut Imports,
+             state: &mut EvalState,
+             lib: &Module,
+             this_ptr: &mut Option<&mut Dynamic>,
+             exprs: &[Expr],
+             level: usize| {
+                let var_name = match exprs.get(0).unwrap() {
+                    Expr::Variable(s) => (s.0).0.clone(),
+                    _ => unreachable!(),
+                };
+                let stmt = exprs.get(1).unwrap();
+                let expr = exprs.get(2).unwrap();
+
+                scope.push(var_name, 0 as INT);
+
+                loop {
+                    engine.eval_expr_from_ast(scope, mods, state, lib, this_ptr, stmt, level)?;
+
+                    if !engine
+                        .eval_expr_from_ast(scope, mods, state, lib, this_ptr, expr, level)?
+                        .as_bool()
+                        .map_err(|_| {
+                            EvalAltResult::ErrorBooleanArgMismatch(
+                                "do-while".into(),
+                                expr.position(),
+                            )
+                        })?
+                    {
+                        break;
+                    }
+                }
+
+                Ok(().into())
+            },
+        )
+        .unwrap();
+
+    assert!(matches!(
+        *engine.add_custom_syntax(&["!"], 0, |_, _, _, _, _, _, _, _| Ok(().into())).expect_err("should error"),
+        LexError::ImproperSymbol(s) if s == "!"
+    ));
+
+    assert_eq!(
+        engine.eval::<INT>(
+            r"
+                do x { x += 1 } while x < 42;
+                x
+            "
+        )?,
+        42
+    );
+
+    Ok(())
+}