Faster processing of this pointer.

src/api/custom_syntax.rs

@@ -109,6 +109,8 @@ impl Expression<'_> {
             #[cfg(not(feature = "no_module"))]
             Expr::Variable(x, ..) if !x.1.is_empty() => None,
             Expr::Variable(x, ..) => Some(x.3.as_str()),
+            #[cfg(not(feature = "no_function"))]
+            Expr::ThisPtr(..) => Some(crate::engine::KEYWORD_THIS),
             Expr::StringConstant(x, ..) => Some(x.as_str()),
             _ => None,
         }

src/ast/expr.rs

@@ -297,6 +297,8 @@ pub enum Expr {
         Option<NonZeroU8>,
         Position,
     ),
+    /// `this`.
+    ThisPtr(Position),
     /// Property access - ((getter, hash), (setter, hash), prop)
     Property(
         Box<(
@@ -375,6 +377,7 @@ impl fmt::Debug for Expr {
                     .entries(x.0.iter().map(|(k, v)| (k, v)))
                     .finish()
             }
+            Self::ThisPtr(..) => f.debug_struct("ThisPtr").finish(),
             Self::Variable(x, i, ..) => {
                 f.write_str("Variable(")?;
 
@@ -632,6 +635,7 @@ impl Expr {
             | Self::Array(..)
             | Self::Map(..)
             | Self::Variable(..)
+            | Self::ThisPtr(..)
             | Self::And(..)
             | Self::Or(..)
             | Self::Coalesce(..)
@@ -662,6 +666,7 @@ impl Expr {
             | Self::Array(.., pos)
             | Self::Map(.., pos)
             | Self::Variable(.., pos)
+            | Self::ThisPtr(pos)
             | Self::And(.., pos)
             | Self::Or(.., pos)
             | Self::Coalesce(.., pos)
@@ -725,6 +730,7 @@ impl Expr {
             | Self::Dot(.., pos)
             | Self::Index(.., pos)
             | Self::Variable(.., pos)
+            | Self::ThisPtr(pos)
             | Self::FnCall(.., pos)
             | Self::MethodCall(.., pos)
             | Self::InterpolatedString(.., pos)
@@ -816,6 +822,7 @@ impl Expr {
             | Self::StringConstant(..)
             | Self::InterpolatedString(..)
             | Self::FnCall(..)
+            | Self::ThisPtr(..)
             | Self::MethodCall(..)
             | Self::Stmt(..)
             | Self::Dot(..)

src/engine.rs

@@ -29,6 +29,7 @@ pub const KEYWORD_IS_SHARED: &str = "is_shared";
 pub const KEYWORD_IS_DEF_VAR: &str = "is_def_var";
 #[cfg(not(feature = "no_function"))]
 pub const KEYWORD_IS_DEF_FN: &str = "is_def_fn";
+#[cfg(not(feature = "no_function"))]
 pub const KEYWORD_THIS: &str = "this";
 #[cfg(not(feature = "no_function"))]
 #[cfg(not(feature = "no_module"))]

src/eval/chaining.rs

@@ -388,6 +388,23 @@ impl Engine {
         let scope2 = ();
 
         match (lhs, new_val) {
+            // this.??? or this[???]
+            (Expr::ThisPtr(var_pos), new_val) => {
+                self.track_operation(global, *var_pos)?;
+
+                #[cfg(feature = "debugging")]
+                self.run_debugger(global, caches, scope, this_ptr.as_deref_mut(), lhs)?;
+
+                if let Some(this_ptr) = this_ptr {
+                    let target = &mut this_ptr.into();
+
+                    self.eval_dot_index_chain_raw(
+                        global, caches, scope2, None, lhs, expr, target, rhs, idx_values, new_val,
+                    )
+                } else {
+                    Err(ERR::ErrorUnboundThis(*var_pos).into())
+                }
+            }
             // id.??? or id[???]
             (Expr::Variable(.., var_pos), new_val) => {
                 self.track_operation(global, *var_pos)?;

src/eval/expr.rs

@@ -2,7 +2,6 @@
 
 use super::{Caches, EvalContext, GlobalRuntimeState, Target};
 use crate::ast::Expr;
-use crate::engine::KEYWORD_THIS;
 use crate::packages::string_basic::{print_with_func, FUNC_TO_STRING};
 use crate::types::dynamic::AccessMode;
 use crate::{Dynamic, Engine, RhaiResult, RhaiResultOf, Scope, SmartString, ERR};
@@ -140,9 +139,7 @@ impl Engine {
 
         let index = match expr {
             // Check if the variable is `this`
-            Expr::Variable(v, None, ..)
+            Expr::ThisPtr(..) => {
-                if v.0.is_none() && v.1.is_empty() && v.3 == KEYWORD_THIS =>
-            {
                 return if let Some(this_ptr) = this_ptr {
                     Ok(this_ptr.into())
                 } else {
@@ -259,13 +256,9 @@ impl Engine {
                 self.eval_fn_call_expr(global, caches, scope, this_ptr, x, *pos)
             }
 
-            Expr::Variable(x, index, var_pos)
+            Expr::ThisPtr(var_pos) => this_ptr
-                if index.is_none() && x.0.is_none() && x.3 == KEYWORD_THIS =>
-            {
-                this_ptr
                 .ok_or_else(|| ERR::ErrorUnboundThis(*var_pos).into())
-                    .cloned()
+                .cloned(),
-            }
 
             Expr::Variable(..) => self
                 .search_namespace(global, caches, scope, this_ptr, expr)
@@ -413,13 +406,7 @@ impl Engine {
                     .and_then(|r| self.check_data_size(r, expr.start_position()))
             }
 
-            Expr::Stmt(x) => {
+            Expr::Stmt(x) => self.eval_stmt_block(global, caches, scope, this_ptr, x, true),
-                if x.is_empty() {
-                    Ok(Dynamic::UNIT)
-                } else {
-                    self.eval_stmt_block(global, caches, scope, this_ptr, x, true)
-                }
-            }
 
             #[cfg(not(feature = "no_index"))]
             Expr::Index(..) => {

src/eval/stmt.rs

@@ -302,7 +302,26 @@ impl Engine {
             Stmt::Assignment(x, ..) => {
                 let (op_info, BinaryExpr { lhs, rhs }) = &**x;
 
-                if let Expr::Variable(x, ..) = lhs {
+                if let Expr::ThisPtr(..) = lhs {
+                    if this_ptr.is_none() {
+                        return Err(ERR::ErrorUnboundThis(lhs.position()).into());
+                    }
+
+                    #[cfg(not(feature = "no_function"))]
+                    {
+                        let rhs_val = self
+                            .eval_expr(global, caches, scope, this_ptr.as_deref_mut(), rhs)?
+                            .flatten();
+
+                        self.track_operation(global, lhs.position())?;
+
+                        let target = &mut this_ptr.unwrap().into();
+
+                        self.eval_op_assignment(global, caches, op_info, lhs, target, rhs_val)?;
+                    }
+                    #[cfg(feature = "no_function")]
+                    unreachable!();
+                } else if let Expr::Variable(x, ..) = lhs {
                     let rhs_val = self
                         .eval_expr(global, caches, scope, this_ptr.as_deref_mut(), rhs)?
                         .flatten();
@@ -342,6 +361,10 @@ impl Engine {
                         // Must be either `var[index] op= val` or `var.prop op= val`.
                         // The return value of any op-assignment (should be `()`) is thrown away and not used.
                         let _ = match lhs {
+                            // this op= rhs (handled above)
+                            Expr::ThisPtr(..) => {
+                                unreachable!("Expr::ThisPtr case is already handled")
+                            }
                             // name op= rhs (handled above)
                             Expr::Variable(..) => {
                                 unreachable!("Expr::Variable case is already handled")

src/optimizer.rs

@@ -901,8 +901,8 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
                 *expr = mem::take(&mut m.0).into_iter().find(|(x, ..)| x.as_str() == prop)
                             .map_or_else(|| Expr::Unit(*pos), |(.., mut expr)| { expr.set_position(*pos); expr });
             }
-            // var.rhs
+            // var.rhs or this.rhs
-            (Expr::Variable(..), rhs) => optimize_expr(rhs, state, true),
+            (Expr::Variable(..) | Expr::ThisPtr(..), rhs) => optimize_expr(rhs, state, true),
             // const.type_of()
             (lhs, Expr::MethodCall(x, pos)) if lhs.is_constant() && x.name == KEYWORD_TYPE_OF && x.args.is_empty() => {
                 if let Some(value) = lhs.get_literal_value() {
@@ -987,8 +987,8 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
                 state.set_dirty();
                 *expr = Expr::CharConstant(s.chars().rev().nth(i.unsigned_abs() as usize - 1).unwrap(), *pos);
             }
-            // var[rhs]
+            // var[rhs] or this[rhs]
-            (Expr::Variable(..), rhs) => optimize_expr(rhs, state, true),
+            (Expr::Variable(..) | Expr::ThisPtr(..), rhs) => optimize_expr(rhs, state, true),
             // lhs[rhs]
             (lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, true); }
         },

src/parser.rs

@@ -7,7 +7,7 @@ use crate::ast::{
     FnCallHashes, Ident, Namespace, OpAssignment, RangeCase, ScriptFnDef, Stmt, StmtBlock,
     StmtBlockContainer, SwitchCasesCollection,
 };
-use crate::engine::{Precedence, KEYWORD_THIS, OP_CONTAINS, OP_NOT};
+use crate::engine::{Precedence, OP_CONTAINS, OP_NOT};
 use crate::eval::{Caches, GlobalRuntimeState};
 use crate::func::{hashing::get_hasher, StraightHashMap};
 use crate::tokenizer::{
@@ -1750,22 +1750,20 @@ impl Engine {
                             settings.pos,
                         )
                     }
-                    // Access to `this` as a variable is OK within a function scope
+                    // Access to `this` as a variable
                     #[cfg(not(feature = "no_function"))]
-                    _ if *s == KEYWORD_THIS && settings.has_flag(ParseSettingFlags::FN_SCOPE) => {
+                    _ if *s == crate::engine::KEYWORD_THIS => {
-                        Expr::Variable(
+                        // OK within a function scope
-                            (None, ns, 0, state.get_interned_string(*s)).into(),
+                        if settings.has_flag(ParseSettingFlags::FN_SCOPE) {
-                            None,
+                            Expr::ThisPtr(settings.pos)
-                            settings.pos,
+                        } else {
-                        )
-                    }
                             // Cannot access to `this` as a variable not in a function scope
-                    _ if *s == KEYWORD_THIS => {
                             let msg = format!("'{s}' can only be used in functions");
                             return Err(
                                 LexError::ImproperSymbol(s.to_string(), msg).into_err(settings.pos)
                             );
                         }
+                    }
                     _ => return Err(PERR::Reserved(s.to_string()).into_err(settings.pos)),
                 }
             }
@@ -2148,10 +2146,8 @@ impl Engine {
         };
 
         match lhs {
-            // const_expr = rhs
+            // this = rhs
-            ref expr if expr.is_constant() => {
+            Expr::ThisPtr(_) => Ok(Stmt::Assignment((op_info, (lhs, rhs).into()).into())),
-                Err(PERR::AssignmentToConstant(String::new()).into_err(lhs.start_position()))
-            }
             // var (non-indexed) = rhs
             Expr::Variable(ref x, None, _) if x.0.is_none() => {
                 Ok(Stmt::Assignment((op_info, (lhs, rhs).into()).into()))
@@ -2186,8 +2182,8 @@ impl Engine {
                 match valid_lvalue {
                     None => {
                         match x.lhs {
-                            // var[???] = rhs, var.??? = rhs
+                            // var[???] = rhs, this[???] = rhs, var.??? = rhs, this.??? = rhs
-                            Expr::Variable(..) => {
+                            Expr::Variable(..) | Expr::ThisPtr(..) => {
                                 Ok(Stmt::Assignment((op_info, (lhs, rhs).into()).into()))
                             }
                             // expr[???] = rhs, expr.??? = rhs
@@ -2200,6 +2196,10 @@ impl Engine {
                     }
                 }
             }
+            // const_expr = rhs
+            ref expr if expr.is_constant() => {
+                Err(PERR::AssignmentToConstant(String::new()).into_err(lhs.start_position()))
+            }
             // ??? && ??? = rhs, ??? || ??? = rhs, xxx ?? xxx = rhs
             Expr::And(..) | Expr::Or(..) | Expr::Coalesce(..) if !op_info.is_op_assignment() => {
                 Err(LexError::ImproperSymbol(

src/types/dynamic.rs

@@ -1186,6 +1186,7 @@ impl Dynamic {
     /// it is cloned into a [`Dynamic`] with a normal value.
     ///
     /// Returns itself if types mismatched.
+    #[allow(unused_mut)]
     pub(crate) fn try_cast_raw<T: Any>(mut self) -> Result<T, Self> {
         // Coded this way in order to maximally leverage potentials for dead-code removal.