prepare transpiling variables

.github/workflows/test.yml

@@ -3,7 +3,7 @@ on:
     push:
         branches: 
             - main
-            - development
+            - develop
             - 'releases/**'
     pull_request:
 
@@ -16,4 +16,4 @@ jobs:
         runs-on: ubuntu-latest
         steps:
             - uses: actions/checkout@v4
-            - run: cargo test --verbose
+            - run: cargo test --verbose --all-features

src/lexical/token.rs

@@ -1,6 +1,12 @@
 //! Contains the [`Token`] struct and its related types.
 
-use std::{borrow::Cow, collections::HashMap, fmt::Display, str::FromStr, sync::OnceLock};
+use std::{
+    borrow::Cow,
+    collections::HashMap,
+    fmt::{Debug, Display},
+    str::FromStr,
+    sync::OnceLock,
+};
 
 use crate::base::{
     self,
@@ -44,6 +50,8 @@ pub enum KeywordKind {
     Tag,
     Of,
     Replace,
+    Int,
+    Bool,
 }
 
 impl Display for KeywordKind {
@@ -107,6 +115,8 @@ impl KeywordKind {
             Self::Tag => "tag",
             Self::Of => "of",
             Self::Replace => "replace",
+            Self::Int => "int",
+            Self::Bool => "bool",
         }
     }
 
@@ -141,7 +151,8 @@ pub enum Token {
     Identifier(Identifier),
     Keyword(Keyword),
     Punctuation(Punctuation),
-    Numeric(Numeric),
+    Integer(Integer),
+    Boolean(Boolean),
     Comment(Comment),
     DocComment(DocComment),
     CommandLiteral(CommandLiteral),
@@ -156,7 +167,8 @@ impl SourceElement for Token {
             Self::Identifier(token) => token.span(),
             Self::Keyword(token) => token.span(),
             Self::Punctuation(token) => token.span(),
-            Self::Numeric(token) => token.span(),
+            Self::Integer(token) => token.span(),
+            Self::Boolean(token) => token.span(),
             Self::Comment(token) => token.span(),
             Self::DocComment(token) => token.span(),
             Self::CommandLiteral(token) => token.span(),
@@ -227,20 +239,72 @@ impl SourceElement for Punctuation {
     }
 }
 
-/// Represents a hardcoded numeric literal value in the source code.
+/// Represents a hardcoded numeric integer literal value in the source code.
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
-#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct Numeric {
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Integer {
     /// Is the span that makes up the token.
     pub span: Span,
 }
 
-impl SourceElement for Numeric {
+impl SourceElement for Integer {
     fn span(&self) -> Span {
         self.span.clone()
     }
 }
 
+impl Integer {
+    /// Returns the integer value of the token.
+    #[must_use]
+    pub fn as_i64(&self) -> i64 {
+        self.span.str().parse().unwrap()
+    }
+}
+
+impl Debug for Integer {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut s = f.debug_struct("Integer");
+        s.field("value", &self.as_i64());
+        s.field("span", &self.span);
+        s.finish()
+    }
+}
+
+/// Represents a hardcoded boolean literal value in the source code.
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Boolean {
+    /// Is the span that makes up the token.
+    pub span: Span,
+}
+
+impl SourceElement for Boolean {
+    fn span(&self) -> Span {
+        self.span.clone()
+    }
+}
+
+impl Boolean {
+    /// Returns the boolean value of the token.
+    #[must_use]
+    pub fn value(&self) -> bool {
+        match self.span.str() {
+            "true" => true,
+            "false" => false,
+            _ => unreachable!("Invalid boolean literal"),
+        }
+    }
+}
+
+impl Debug for Boolean {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut s = f.debug_struct("Boolean");
+        s.field("value", &self.value());
+        s.field("span", &self.span);
+        s.finish()
+    }
+}
+
 /// Represents a hardcoded string literal value in the source code.
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -590,16 +654,13 @@ impl Token {
         let word = span.str();
 
         // Checks if the word is a keyword
-        KeywordKind::from_str(word).ok().map_or_else(
-            || Identifier { span: span.clone() }.into(),
-            |kw| {
-                Keyword {
-                    span: span.clone(),
-                    keyword: kw,
+        if let Ok(kw) = KeywordKind::from_str(word) {
+            Keyword { span, keyword: kw }.into()
+        } else if bool::from_str(word).is_ok() {
+            Boolean { span }.into()
+        } else {
+            Identifier { span }.into()
         }
-                .into()
-            },
-        )
     }
 
     /// Handles a sequence starting with a slash
@@ -684,11 +745,11 @@ impl Token {
     }
 
     /// Handles a sequence of digits
-    fn handle_numeric_literal(iter: &mut SourceIterator, start: usize) -> Self {
+    fn handle_integer_literal(iter: &mut SourceIterator, start: usize) -> Self {
         // Tokenizes the whole number part
         Self::walk_iter(iter, |character| character.is_ascii_digit());
 
-        Numeric {
+        Integer {
             span: Self::create_span(start, iter),
         }
         .into()
@@ -871,9 +932,9 @@ impl Token {
         else if character == '`' {
             Self::handle_macro_string_literal(iter, start)
         }
-        // Found numeric literal
+        // Found integer literal
         else if character.is_ascii_digit() {
-            Ok(Self::handle_numeric_literal(iter, start))
+            Ok(Self::handle_integer_literal(iter, start))
         }
         // Found a punctuation
         else if character.is_ascii_punctuation() {

src/semantic/mod.rs

@@ -11,7 +11,7 @@ use error::{
 
 use crate::{
     base::{self, source_file::SourceElement as _, Handler},
-    lexical::token::{MacroStringLiteral, MacroStringLiteralPart},
+    lexical::token::{KeywordKind, MacroStringLiteral, MacroStringLiteralPart},
     syntax::syntax_tree::{
         condition::{
             BinaryCondition, Condition, ParenthesizedCondition, PrimaryCondition, UnaryCondition,
@@ -24,7 +24,7 @@ use crate::{
                 Conditional, Else, ExecuteBlock, ExecuteBlockHead, ExecuteBlockHeadItem as _,
                 ExecuteBlockTail,
             },
-            Block, Grouping, Run, Semicolon, Statement,
+            Block, Grouping, Run, Semicolon, SemicolonStatement, Statement, VariableDeclaration,
         },
         AnyStringLiteral,
     },
@@ -291,7 +291,8 @@ impl Semicolon {
         macro_names: &HashSet<String>,
         handler: &impl Handler<base::Error>,
     ) -> Result<(), error::Error> {
-        match self.expression() {
+        match self.statement() {
+            SemicolonStatement::Expression(expr) => match expr {
                 Expression::Primary(Primary::FunctionCall(func)) => {
                     func.analyze_semantics(function_names, macro_names, handler)
                 }
@@ -302,6 +303,10 @@ impl Semicolon {
                     handler.receive(error.clone());
                     Err(error)
                 }
+            },
+            SemicolonStatement::VariableDeclaration(decl) => {
+                decl.analyze_semantics(function_names, macro_names, handler)
+            }
         }
     }
 }
@@ -456,7 +461,7 @@ impl Primary {
             Self::FunctionCall(func) => {
                 func.analyze_semantics(function_names, macro_names, handler)
             }
-            Self::Lua(_) | Self::StringLiteral(_) => Ok(()),
+            Self::Lua(_) | Self::StringLiteral(_) | Self::Integer(_) | Self::Boolean(_) => Ok(()),
             Self::MacroStringLiteral(literal) => literal.analyze_semantics(macro_names, handler),
         }
     }
@@ -514,6 +519,95 @@ impl AnyStringLiteral {
     }
 }
 
+impl VariableDeclaration {
+    /// Analyzes the semantics of a variable declaration.
+    pub fn analyze_semantics(
+        &self,
+        function_names: &HashSet<String>,
+        macro_names: &HashSet<String>,
+        handler: &impl Handler<base::Error>,
+    ) -> Result<(), error::Error> {
+        match self {
+            Self::Array(array) => array.assignment().as_ref().map_or(Ok(()), |assignment| {
+                assignment
+                    .expression()
+                    .analyze_semantics(function_names, macro_names, handler)
+            }),
+            Self::Single(single) => {
+                if let Some(assignment) = single.assignment() {
+                    let err = match single.variable_type().keyword {
+                        KeywordKind::Int => !matches!(
+                            assignment.expression(),
+                            // TODO: also allow macro identifier but not macro string literal
+                            Expression::Primary(
+                                Primary::Integer(_) | Primary::Lua(_) | Primary::FunctionCall(_)
+                            )
+                        ),
+                        KeywordKind::Bool => !matches!(
+                            assignment.expression(),
+                            Expression::Primary(Primary::Boolean(_) | Primary::Lua(_))
+                        ),
+                        _ => false,
+                    };
+                    if err {
+                        let err = error::Error::UnexpectedExpression(UnexpectedExpression(
+                            assignment.expression().clone(),
+                        ));
+                        handler.receive(err.clone());
+                        return Err(err);
+                    }
+                    assignment
+                        .expression()
+                        .analyze_semantics(function_names, macro_names, handler)
+                } else {
+                    Ok(())
+                }
+            }
+            Self::Score(score) => {
+                if let Some((_, assignment)) = score.target_assignment() {
+                    // TODO: also allow macro identifier but not macro string literal
+                    if !matches!(
+                        assignment.expression(),
+                        Expression::Primary(
+                            Primary::Integer(_) | Primary::Lua(_) | Primary::FunctionCall(_)
+                        )
+                    ) {
+                        let err = error::Error::UnexpectedExpression(UnexpectedExpression(
+                            assignment.expression().clone(),
+                        ));
+                        handler.receive(err.clone());
+                        return Err(err);
+                    }
+                    assignment
+                        .expression()
+                        .analyze_semantics(function_names, macro_names, handler)
+                } else {
+                    Ok(())
+                }
+            }
+            Self::Tag(tag) => {
+                if let Some((_, assignment)) = tag.target_assignment() {
+                    if !matches!(
+                        assignment.expression(),
+                        Expression::Primary(Primary::Boolean(_) | Primary::Lua(_))
+                    ) {
+                        let err = error::Error::UnexpectedExpression(UnexpectedExpression(
+                            assignment.expression().clone(),
+                        ));
+                        handler.receive(err.clone());
+                        return Err(err);
+                    }
+                    assignment
+                        .expression()
+                        .analyze_semantics(function_names, macro_names, handler)
+                } else {
+                    Ok(())
+                }
+            }
+        }
+    }
+}
+
 impl PrimaryCondition {
     /// Analyzes the semantics of a primary condition.
     pub fn analyze_semantics(

src/serde.rs

@@ -14,6 +14,7 @@ use serde::{
 
 use crate::base::source_file::SourceFile;
 
+thread_local! {
     static DEDUPLICATE_SOURCE_FILES: LazyLock<RwLock<bool>> = LazyLock::new(|| RwLock::new(false));
 
     static SERIALIZE_DATA: LazyLock<Mutex<SerializeData>> =
@@ -21,6 +22,7 @@ static SERIALIZE_DATA: LazyLock<Mutex<SerializeData>> =
 
     static DESERIALIZE_DATA: LazyLock<RwLock<Option<DeserializeData>>> =
         LazyLock::new(|| RwLock::new(None));
+}
 
 /// Wrapper to remove duplicate source file data during (de-)serialization
 #[expect(clippy::module_name_repetitions)]
@@ -35,20 +37,27 @@ where
     where
         S: serde::Serializer,
     {
-        *DEDUPLICATE_SOURCE_FILES.write().unwrap() = true;
-        SERIALIZE_DATA.lock().unwrap().clear();
+        DEDUPLICATE_SOURCE_FILES.with(|d| *d.write().unwrap() = true);
+        SERIALIZE_DATA.with(|d| d.lock().unwrap().clear());
+        // hold guard so no other can serialize at the same time in same thread
+        let s = DEDUPLICATE_SOURCE_FILES.with(|d| {
+            let guard = d.read().unwrap();
             let mut serialized_data = flexbuffers::FlexbufferSerializer::new();
             self.0
                 .serialize(&mut serialized_data)
                 .map_err(|_| serde::ser::Error::custom("could not buffer serialization"))?;
             drop(serialized_data);
             let mut s = serializer.serialize_struct("SerdeWrapper", 3)?;
-        s.serialize_field(
-            "source_files",
-            &SERIALIZE_DATA.lock().unwrap().id_to_source_file,
-        )?;
+
+            SERIALIZE_DATA.with(|d| {
+                s.serialize_field("source_files", &d.lock().unwrap().id_to_source_file)
+            })?;
             s.serialize_field("data", &self.0)?;
-        *DEDUPLICATE_SOURCE_FILES.write().unwrap() = false;
+            drop(guard);
+            Ok(s)
+        })?;
+
+        DEDUPLICATE_SOURCE_FILES.with(|d| *d.write().unwrap() = false);
         s.end()
     }
 }
@@ -87,11 +96,13 @@ where
                 let source_files: BTreeMap<u64, SourceFile> = seq
                     .next_element()?
                     .ok_or_else(|| de::Error::invalid_length(0, &self))?;
-                *DESERIALIZE_DATA.write().unwrap() = Some(DeserializeData {
+                DESERIALIZE_DATA.with(|d| {
+                    *d.write().unwrap() = Some(DeserializeData {
                         id_to_source_file: source_files
                             .into_iter()
                             .map(|(k, v)| (k, Arc::new(v)))
                             .collect(),
+                    })
                 });
                 let data = seq
                     .next_element()?
@@ -113,12 +124,14 @@ where
                             if data.is_some() {
                                 return Err(de::Error::duplicate_field("data"));
                             }
-                            *DESERIALIZE_DATA.write().unwrap() =
+                            DESERIALIZE_DATA.with(|d| {
+                                *d.write().unwrap() =
                                     source_files.as_ref().map(|source_files| DeserializeData {
                                         id_to_source_file: source_files
                                             .iter()
                                             .map(|(&k, v)| (k, Arc::new(v.clone())))
                                             .collect(),
+                                    })
                             });
                             data = Some(map.next_value()?);
                         }
@@ -136,14 +149,14 @@ where
             }
         }
 
-        *DEDUPLICATE_SOURCE_FILES.write().unwrap() = true;
-        *DESERIALIZE_DATA.write().unwrap() = None;
+        DEDUPLICATE_SOURCE_FILES.with(|d| *d.write().unwrap() = true);
+        DESERIALIZE_DATA.with(|d| *d.write().unwrap() = None);
         let res = deserializer.deserialize_struct(
             "SerdeWrapper",
             &["source_files", "data"],
             WrapperVisitor(PhantomData::<T>),
         );
-        *DEDUPLICATE_SOURCE_FILES.write().unwrap() = false;
+        DEDUPLICATE_SOURCE_FILES.with(|d| *d.write().unwrap() = false);
 
         res
     }
@@ -200,9 +213,11 @@ pub mod source_file {
     where
         S: serde::Serializer,
     {
-        if *DEDUPLICATE_SOURCE_FILES.read().unwrap() {
-            let mut data = SERIALIZE_DATA.lock().unwrap();
+        if DEDUPLICATE_SOURCE_FILES.with(|d| *d.read().unwrap()) {
+            SERIALIZE_DATA.with(|d| {
+                let mut data = d.lock().unwrap();
                 serializer.serialize_u64(data.get_id_of(this))
+            })
         } else {
             this.as_ref().serialize(serializer)
         }
@@ -212,17 +227,18 @@ pub mod source_file {
     where
         D: serde::Deserializer<'de>,
     {
-        if *DEDUPLICATE_SOURCE_FILES.read().unwrap() {
+        if DEDUPLICATE_SOURCE_FILES.with(|d| *d.read().unwrap()) {
             let id = u64::deserialize(deserializer)?;
-            Ok(DESERIALIZE_DATA
-                .read()
+            Ok(DESERIALIZE_DATA.with(|d| {
+                d.read()
                     .unwrap()
                     .as_ref()
                     .ok_or_else(|| de::Error::custom("SourceFiles do not have been loaded yet"))?
                     .id_to_source_file
                     .get(&id)
                     .map(Arc::clone)
-                .ok_or_else(|| serde::de::Error::custom("invalid source_file id"))?)
+                    .ok_or_else(|| serde::de::Error::custom("invalid source_file id"))
+            }))?
         } else {
             Ok(Arc::new(SourceFile::deserialize(deserializer)?))
         }

src/syntax/error.rs

@@ -32,7 +32,8 @@ pub enum SyntaxKind {
     Keyword(KeywordKind),
     Identifier,
     Declaration,
-    Numeric,
+    Integer,
+    Boolean,
     StringLiteral,
     MacroStringLiteral,
     AnyStringLiteral,
@@ -69,7 +70,8 @@ impl SyntaxKind {
             Self::Punctuation(char) => format!("a punctuation token `{char}`"),
             Self::Keyword(keyword) => format!("a keyword token `{}`", keyword.as_str()),
             Self::Declaration => "a declaration token".to_string(),
-            Self::Numeric => "a numeric token".to_string(),
+            Self::Integer => "an integer token".to_string(),
+            Self::Boolean => "a boolean token".to_string(),
             Self::StringLiteral => "a string literal".to_string(),
             Self::MacroStringLiteral => "a macro string literal".to_string(),
             Self::AnyStringLiteral => "a (macro) string literal".to_string(),
@@ -106,7 +108,8 @@ impl Display for UnexpectedSyntax {
             Some(Token::Punctuation(punctuation)) => {
                 format!("a punctuation token `{}`", punctuation.punctuation)
             }
-            Some(Token::Numeric(..)) => "a numeric token".to_string(),
+            Some(Token::Integer(..)) => "an integer token".to_string(),
+            Some(Token::Boolean(..)) => "a boolean token".to_string(),
             Some(Token::CommandLiteral(..)) => "a literal command token".to_string(),
             Some(Token::StringLiteral(..)) => "a string literal token".to_string(),
             Some(Token::MacroStringLiteral(..)) => "a macro string literal token".to_string(),

src/syntax/parser.rs

@@ -7,7 +7,7 @@ use crate::{
     base::{self, Handler},
     lexical::{
         token::{
-            Identifier, Keyword, KeywordKind, MacroStringLiteral, Numeric, Punctuation,
+            Identifier, Integer, Keyword, KeywordKind, MacroStringLiteral, Punctuation,
             StringLiteral, Token,
         },
         token_stream::{Delimited, Delimiter, TokenStream, TokenTree},
@@ -399,16 +399,16 @@ impl<'a> Frame<'a> {
         }
     }
 
-    /// Expects the next [`Token`] to be an [`Numeric`], and returns it.
+    /// Expects the next [`Token`] to be an [`Integer`], and returns it.
     ///
     /// # Errors
     /// If the next [`Token`] is not an [`Identifier`].
-    pub fn parse_numeric(&mut self, handler: &impl Handler<Error>) -> ParseResult<Numeric> {
+    pub fn parse_integer(&mut self, handler: &impl Handler<Error>) -> ParseResult<Integer> {
         match self.next_significant_token() {
-            Reading::Atomic(Token::Numeric(ident)) => Ok(ident),
+            Reading::Atomic(Token::Integer(ident)) => Ok(ident),
             found => {
                 let err = Error::UnexpectedSyntax(UnexpectedSyntax {
-                    expected: SyntaxKind::Numeric,
+                    expected: SyntaxKind::Integer,
                     found: found.into_token(),
                 });
                 handler.receive(err.clone());

src/syntax/syntax_tree/expression.rs

@@ -11,7 +11,8 @@ use crate::{
     },
     lexical::{
         token::{
-            Identifier, Keyword, KeywordKind, MacroStringLiteral, Punctuation, StringLiteral, Token,
+            Boolean, Identifier, Integer, Keyword, KeywordKind, MacroStringLiteral, Punctuation,
+            StringLiteral, Token,
         },
         token_stream::Delimiter,
     },
@@ -53,8 +54,10 @@ impl SourceElement for Expression {
 ///
 /// ``` ebnf
 /// Primary:
-///     FunctionCall
+///     Integer
+///     | Boolean
 ///     | StringLiteral
+///     | FunctionCall
 ///     | MacroStringLiteral
 ///     | LuaCode
 /// ```
@@ -62,8 +65,10 @@ impl SourceElement for Expression {
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, EnumAsInner)]
 pub enum Primary {
-    FunctionCall(FunctionCall),
+    Integer(Integer),
+    Boolean(Boolean),
     StringLiteral(StringLiteral),
+    FunctionCall(FunctionCall),
     MacroStringLiteral(MacroStringLiteral),
     Lua(Box<LuaCode>),
 }
@@ -71,8 +76,10 @@ pub enum Primary {
 impl SourceElement for Primary {
     fn span(&self) -> Span {
         match self {
-            Self::FunctionCall(function_call) => function_call.span(),
+            Self::Integer(int) => int.span(),
+            Self::Boolean(bool) => bool.span(),
             Self::StringLiteral(string_literal) => string_literal.span(),
+            Self::FunctionCall(function_call) => function_call.span(),
             Self::MacroStringLiteral(macro_string_literal) => macro_string_literal.span(),
             Self::Lua(lua_code) => lua_code.span(),
         }
@@ -224,6 +231,22 @@ impl<'a> Parser<'a> {
                 }
             }
 
+            // integer expression
+            Reading::Atomic(Token::Integer(int)) => {
+                // eat the int
+                self.forward();
+
+                Ok(Primary::Integer(int))
+            }
+
+            // boolean expression
+            Reading::Atomic(Token::Boolean(bool)) => {
+                // eat the bool
+                self.forward();
+
+                Ok(Primary::Boolean(bool))
+            }
+
             // string literal expression
             Reading::Atomic(Token::StringLiteral(literal)) => {
                 // eat the string literal

src/syntax/syntax_tree/statement.rs

@@ -3,27 +3,31 @@
 pub mod execute_block;
 
 use derive_more::From;
+use enum_as_inner::EnumAsInner;
 use getset::Getters;
 
 use crate::{
     base::{
         self,
         source_file::{SourceElement, Span},
-        Handler,
+        Handler, VoidHandler,
     },
     lexical::{
-        token::{CommandLiteral, DocComment, Keyword, KeywordKind, Punctuation, Token},
+        token::{
+            CommandLiteral, DocComment, Identifier, Integer, Keyword, KeywordKind, Punctuation,
+            Token,
+        },
         token_stream::Delimiter,
     },
     syntax::{
-        error::ParseResult,
+        error::{Error, ParseResult, SyntaxKind, UnexpectedSyntax},
         parser::{Parser, Reading},
     },
 };
 
 use self::execute_block::ExecuteBlock;
 
-use super::expression::Expression;
+use super::{expression::Expression, AnyStringLiteral};
 
 /// Represents a statement in the syntax tree.
 ///
@@ -189,7 +193,7 @@ impl SourceElement for Grouping {
 /// Syntax Synopsis:
 /// ``` ebnf
 /// Semicolon:
-///    Expression ';'
+///    SemicolonStatement ';'
 ///   ;
 /// ```
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
@@ -197,7 +201,7 @@ impl SourceElement for Grouping {
 pub struct Semicolon {
     /// The expression of the semicolon statement.
     #[get = "pub"]
-    expression: Expression,
+    statement: SemicolonStatement,
     /// The semicolon of the semicolon statement.
     #[get = "pub"]
     semicolon: Punctuation,
@@ -205,7 +209,7 @@ pub struct Semicolon {
 
 impl SourceElement for Semicolon {
     fn span(&self) -> Span {
-        self.expression
+        self.statement
             .span()
             .join(&self.semicolon.span())
             .expect("The span of the semicolon statement is invalid.")
@@ -215,8 +219,373 @@ impl SourceElement for Semicolon {
 impl Semicolon {
     /// Dissolves the [`Semicolon`] into its components.
     #[must_use]
-    pub fn dissolve(self) -> (Expression, Punctuation) {
-        (self.expression, self.semicolon)
+    pub fn dissolve(self) -> (SemicolonStatement, Punctuation) {
+        (self.statement, self.semicolon)
+    }
+}
+
+/// Represents a statement that ends with a semicolon in the syntax tree.
+///
+/// Syntax Synopsis:
+/// ``` ebnf
+/// SemicolonStatement:
+///    (Expression | VariableDeclaration)
+///    ';'
+///   ;
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, From, EnumAsInner)]
+pub enum SemicolonStatement {
+    /// An expression that ends with a semicolon.
+    Expression(Expression),
+    /// A variable declaration.
+    VariableDeclaration(VariableDeclaration),
+}
+
+impl SourceElement for SemicolonStatement {
+    fn span(&self) -> Span {
+        match self {
+            Self::Expression(expression) => expression.span(),
+            Self::VariableDeclaration(declaration) => declaration.span(),
+        }
+    }
+}
+
+/// Represents a variable declaration in the syntax tree.
+///
+/// Syntax Synopsis:
+///
+/// ```ebnf
+/// VariableDeclaration:
+///    SingleVariableDeclaration
+///    | ArrayVariableDeclaration
+///    | ScoreVariableDeclaration
+///    | TagVariableDeclaration
+///    ;
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, From, EnumAsInner)]
+#[allow(missing_docs)]
+pub enum VariableDeclaration {
+    Single(SingleVariableDeclaration),
+    Array(ArrayVariableDeclaration),
+    Score(ScoreVariableDeclaration),
+    Tag(TagVariableDeclaration),
+}
+
+impl SourceElement for VariableDeclaration {
+    fn span(&self) -> Span {
+        match self {
+            Self::Single(declaration) => declaration.span(),
+            Self::Array(declaration) => declaration.span(),
+            Self::Score(declaration) => declaration.span(),
+            Self::Tag(declaration) => declaration.span(),
+        }
+    }
+}
+
+impl VariableDeclaration {
+    /// Get the identifier of the variable declaration
+    #[must_use]
+    pub fn identifier(&self) -> &Identifier {
+        match self {
+            Self::Single(declaration) => &declaration.identifier,
+            Self::Array(declaration) => &declaration.identifier,
+            Self::Score(declaration) => &declaration.identifier,
+            Self::Tag(declaration) => &declaration.identifier,
+        }
+    }
+
+    /// Get the type of the variable declaration
+    #[must_use]
+    pub fn variable_type(&self) -> &Keyword {
+        match self {
+            Self::Single(declaration) => &declaration.variable_type,
+            Self::Array(declaration) => &declaration.variable_type,
+            Self::Score(declaration) => &declaration.int_keyword,
+            Self::Tag(declaration) => &declaration.bool_keyword,
+        }
+    }
+}
+
+/// Represents a variable assignment.
+///
+/// Syntax Synopsis:
+///
+/// ```ebnf
+/// VariableDeclarationAssignment:
+///     '=' Expression
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Getters)]
+pub struct VariableDeclarationAssignment {
+    /// The equals sign of the variable declaration.
+    #[get = "pub"]
+    equals: Punctuation,
+    /// The expression of the variable declaration.
+    #[get = "pub"]
+    expression: Expression,
+}
+
+impl SourceElement for VariableDeclarationAssignment {
+    fn span(&self) -> Span {
+        self.equals
+            .span()
+            .join(&self.expression.span())
+            .expect("The span of the variable declaration assignment is invalid.")
+    }
+}
+
+impl VariableDeclarationAssignment {
+    /// Dissolves the [`VariableDeclarationAssignment`] into its components.
+    #[must_use]
+    pub fn dissolve(self) -> (Punctuation, Expression) {
+        (self.equals, self.expression)
+    }
+}
+
+/// Represents a single variable declaration in the syntax tree.
+///
+/// Syntax Synopsis:
+///
+/// ```ebnf
+/// SingleVariableDeclaration:
+///     ('int' | 'bool') identifier VariableDeclarationAssignment?
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Getters)]
+pub struct SingleVariableDeclaration {
+    /// The type of the variable.
+    #[get = "pub"]
+    variable_type: Keyword,
+    /// The identifier of the variable.
+    #[get = "pub"]
+    identifier: Identifier,
+    /// The optional assignment of the variable.
+    #[get = "pub"]
+    assignment: Option<VariableDeclarationAssignment>,
+}
+
+impl SourceElement for SingleVariableDeclaration {
+    fn span(&self) -> Span {
+        self.variable_type
+            .span()
+            .join(
+                &self
+                    .assignment
+                    .as_ref()
+                    .map_or_else(|| self.identifier.span(), SourceElement::span),
+            )
+            .expect("The span of the single variable declaration is invalid.")
+    }
+}
+
+impl SingleVariableDeclaration {
+    /// Dissolves the [`SingleVariableDeclaration`] into its components.
+    #[must_use]
+    pub fn dissolve(self) -> (Keyword, Identifier, Option<VariableDeclarationAssignment>) {
+        (self.variable_type, self.identifier, self.assignment)
+    }
+}
+
+/// Represents an array variable declaration in the syntax tree.
+///
+/// Syntax Synopsis:
+///
+/// ```ebnf
+/// ArrayVariableDeclaration:
+///     ('int' | 'bool') identifier '[' integer ']' VariableDeclarationAssignment?
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Getters)]
+pub struct ArrayVariableDeclaration {
+    /// The type of the variable.
+    #[get = "pub"]
+    variable_type: Keyword,
+    /// The identifier of the variable.
+    #[get = "pub"]
+    identifier: Identifier,
+    /// The opening bracket of the array.
+    #[get = "pub"]
+    open_bracket: Punctuation,
+    /// The array size
+    #[get = "pub"]
+    size: Integer,
+    /// The closing bracket of the array.
+    #[get = "pub"]
+    close_bracket: Punctuation,
+    /// The optional assignment of the variable.
+    #[get = "pub"]
+    assignment: Option<VariableDeclarationAssignment>,
+}
+
+impl SourceElement for ArrayVariableDeclaration {
+    fn span(&self) -> Span {
+        self.variable_type
+            .span()
+            .join(
+                &self
+                    .assignment
+                    .as_ref()
+                    .map_or_else(|| self.close_bracket.span(), SourceElement::span),
+            )
+            .expect("The span of the array variable declaration is invalid.")
+    }
+}
+
+impl ArrayVariableDeclaration {
+    /// Dissolves the [`ArrayVariableDeclaration`] into its components.
+    #[must_use]
+    pub fn dissolve(
+        self,
+    ) -> (
+        Keyword,
+        Identifier,
+        Punctuation,
+        Integer,
+        Punctuation,
+        Option<VariableDeclarationAssignment>,
+    ) {
+        (
+            self.variable_type,
+            self.identifier,
+            self.open_bracket,
+            self.size,
+            self.close_bracket,
+            self.assignment,
+        )
+    }
+}
+
+type CriteriaSelection = (Punctuation, AnyStringLiteral, Punctuation);
+
+/// Represents a scoreboard variable declaration in the syntax tree.
+///
+/// Syntax Synopsis:
+///
+/// ```ebnf
+/// ScoreVariableDeclaration:
+///     'int' ('<' AnyStringLiteral '>')? identifier '[' AnyStringLiteral? ']' VariableDeclarationAssignment?
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Getters)]
+pub struct ScoreVariableDeclaration {
+    /// `int` keyword
+    #[get = "pub"]
+    int_keyword: Keyword,
+    /// The scoreboard criteria
+    #[get = "pub"]
+    criteria: Option<CriteriaSelection>,
+    /// The identifier of the variable.
+    #[get = "pub"]
+    identifier: Identifier,
+    /// Opening bracket of the score variable
+    #[get = "pub"]
+    open_bracket: Punctuation,
+    /// Closing bracket of the score variable
+    #[get = "pub"]
+    close_bracket: Punctuation,
+    /// The optional assignment of the variable.
+    #[get = "pub"]
+    target_assignment: Option<(AnyStringLiteral, VariableDeclarationAssignment)>,
+}
+
+impl SourceElement for ScoreVariableDeclaration {
+    fn span(&self) -> Span {
+        self.int_keyword
+            .span()
+            .join(&self.target_assignment.as_ref().map_or_else(
+                || self.close_bracket.span(),
+                |(_, assignment)| assignment.span(),
+            ))
+            .expect("The span of the score variable declaration is invalid.")
+    }
+}
+
+impl ScoreVariableDeclaration {
+    /// Dissolves the [`ScoreVariableDeclaration`] into its components.
+    #[expect(clippy::type_complexity)]
+    #[must_use]
+    pub fn dissolve(
+        self,
+    ) -> (
+        Keyword,
+        Option<CriteriaSelection>,
+        Identifier,
+        Punctuation,
+        Punctuation,
+        Option<(AnyStringLiteral, VariableDeclarationAssignment)>,
+    ) {
+        (
+            self.int_keyword,
+            self.criteria,
+            self.identifier,
+            self.open_bracket,
+            self.close_bracket,
+            self.target_assignment,
+        )
+    }
+}
+
+/// Represents a tag variable declaration in the syntax tree.
+///
+/// Syntax Synopsis:
+///
+/// ```ebnf
+/// TagVariableDeclaration:
+///     'bool' identifier '[' AnyStringLiteral? ']' VariableDeclarationAssignment?
+/// ```
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Getters)]
+pub struct TagVariableDeclaration {
+    /// `bool` keyword
+    #[get = "pub"]
+    bool_keyword: Keyword,
+    /// The identifier of the variable.
+    #[get = "pub"]
+    identifier: Identifier,
+    /// Opening bracket of the score variable
+    #[get = "pub"]
+    open_bracket: Punctuation,
+    /// Closing bracket of the score variable
+    #[get = "pub"]
+    close_bracket: Punctuation,
+    /// The optional assignment of the variable.
+    #[get = "pub"]
+    target_assignment: Option<(AnyStringLiteral, VariableDeclarationAssignment)>,
+}
+
+impl SourceElement for TagVariableDeclaration {
+    fn span(&self) -> Span {
+        self.bool_keyword
+            .span()
+            .join(&self.target_assignment.as_ref().map_or_else(
+                || self.close_bracket.span(),
+                |(_, assignment)| assignment.span(),
+            ))
+            .expect("The span of the tag variable declaration is invalid.")
+    }
+}
+
+impl TagVariableDeclaration {
+    /// Dissolves the [`TagVariableDeclaration`] into its components.
+    #[must_use]
+    pub fn dissolve(
+        self,
+    ) -> (
+        Keyword,
+        Identifier,
+        Punctuation,
+        Punctuation,
+        Option<(AnyStringLiteral, VariableDeclarationAssignment)>,
+    ) {
+        (
+            self.bool_keyword,
+            self.identifier,
+            self.open_bracket,
+            self.close_bracket,
+            self.target_assignment,
+        )
     }
 }
 
@@ -333,17 +702,225 @@ impl<'a> Parser<'a> {
             }
 
             // semicolon statement
-            _ => {
-                let expression = self.parse_expression(handler)?;
+            _ => self.parse_semicolon(handler).map(Statement::Semicolon),
+        }
+    }
+
+    /// Parses a [`Semicolon`].
+    #[tracing::instrument(level = "trace", skip_all)]
+    pub fn parse_semicolon(
+        &mut self,
+        handler: &impl Handler<base::Error>,
+    ) -> ParseResult<Semicolon> {
+        let statement = match self.stop_at_significant() {
+            Reading::Atomic(Token::Keyword(keyword))
+                if matches!(keyword.keyword, KeywordKind::Int | KeywordKind::Bool) =>
+            {
+                self.parse_variable_declaration(handler)
+                    .map(SemicolonStatement::VariableDeclaration)
+            }
+            _ => self
+                .parse_expression(handler)
+                .map(SemicolonStatement::Expression),
+        }?;
+
         let semicolon = self.parse_punctuation(';', true, handler)?;
 
-                tracing::trace!("Parsed semicolon statement: {:?}", expression);
-
-                Ok(Statement::Semicolon(Semicolon {
-                    expression,
+        Ok(Semicolon {
+            statement,
             semicolon,
+        })
+    }
+
+    /// Parses a [`VariableDeclaration`].
+    #[tracing::instrument(level = "trace", skip_all)]
+    pub fn parse_variable_declaration(
+        &mut self,
+        handler: &impl Handler<base::Error>,
+    ) -> ParseResult<VariableDeclaration> {
+        enum IndexingType {
+            IntegerSize(Integer),
+            AnyString(AnyStringLiteral),
+            None,
+        }
+
+        let variable_type = match self.stop_at_significant() {
+            Reading::Atomic(Token::Keyword(keyword))
+                if matches!(keyword.keyword, KeywordKind::Int | KeywordKind::Bool) =>
+            {
+                self.forward();
+                keyword
+            }
+            unexpected => {
+                let err = Error::UnexpectedSyntax(UnexpectedSyntax {
+                    expected: SyntaxKind::Either(&[
+                        SyntaxKind::Keyword(KeywordKind::Int),
+                        SyntaxKind::Keyword(KeywordKind::Bool),
+                    ]),
+                    found: unexpected.into_token(),
+                });
+                handler.receive(err.clone());
+                return Err(err);
+            }
+        };
+
+        let criteria_selection = if variable_type.keyword == KeywordKind::Int {
+            self.try_parse(|p| {
+                let open = p.parse_punctuation('<', true, &VoidHandler)?;
+                let criteria = p.parse_any_string_literal(&VoidHandler)?;
+                let close = p.parse_punctuation('>', true, &VoidHandler)?;
+                Ok((open, criteria, close))
+            })
+            .ok()
+        } else {
+            None
+        };
+
+        // read identifier
+        self.stop_at_significant();
+        let identifier = self.parse_identifier(handler)?;
+
+        match self.stop_at_significant() {
+            Reading::IntoDelimited(punc) if punc.punctuation == '[' => {
+                let tree = self.step_into(
+                    Delimiter::Bracket,
+                    |p| {
+                        let res = match p.stop_at_significant() {
+                            Reading::Atomic(Token::Integer(int)) => {
+                                p.forward();
+                                IndexingType::IntegerSize(int)
+                            }
+
+                            Reading::Atomic(Token::StringLiteral(s)) => {
+                                let selector = AnyStringLiteral::from(s);
+                                p.forward();
+                                IndexingType::AnyString(selector)
+                            }
+                            Reading::Atomic(Token::MacroStringLiteral(s)) => {
+                                let selector = AnyStringLiteral::from(s);
+                                p.forward();
+                                IndexingType::AnyString(selector)
+                            }
+
+                            Reading::DelimitedEnd(punc) if punc.punctuation == ']' => {
+                                IndexingType::None
+                            }
+
+                            unexpected => {
+                                let err = Error::UnexpectedSyntax(UnexpectedSyntax {
+                                    expected: SyntaxKind::Either(&[
+                                        SyntaxKind::Integer,
+                                        SyntaxKind::AnyStringLiteral,
+                                    ]),
+                                    found: unexpected.into_token(),
+                                });
+                                handler.receive(err.clone());
+                                return Err(err);
+                            }
+                        };
+
+                        Ok(res)
+                    },
+                    handler,
+                )?;
+
+                let open_bracket = tree.open;
+                let close_bracket = tree.close;
+                let inner = tree.tree?;
+
+                match inner {
+                    IndexingType::IntegerSize(size) => {
+                        let assignment = self
+                            .try_parse(|p| {
+                                // read equals sign
+                                let equals = p.parse_punctuation('=', true, handler)?;
+
+                                // read expression
+                                let expression = p.parse_expression(handler)?;
+
+                                Ok(VariableDeclarationAssignment { equals, expression })
+                            })
+                            .ok();
+
+                        Ok(VariableDeclaration::Array(ArrayVariableDeclaration {
+                            variable_type,
+                            identifier,
+                            open_bracket,
+                            size,
+                            close_bracket,
+                            assignment,
                         }))
                     }
+                    IndexingType::AnyString(selector) => {
+                        let equals = self.parse_punctuation('=', true, handler)?;
+                        let expression = self.parse_expression(handler)?;
+
+                        let assignment = VariableDeclarationAssignment { equals, expression };
+
+                        match variable_type.keyword {
+                            KeywordKind::Int => {
+                                Ok(VariableDeclaration::Score(ScoreVariableDeclaration {
+                                    int_keyword: variable_type,
+                                    criteria: criteria_selection,
+                                    identifier,
+                                    open_bracket,
+                                    close_bracket,
+                                    target_assignment: Some((selector, assignment)),
+                                }))
+                            }
+                            KeywordKind::Bool => {
+                                Ok(VariableDeclaration::Tag(TagVariableDeclaration {
+                                    bool_keyword: variable_type,
+                                    identifier,
+                                    open_bracket,
+                                    close_bracket,
+                                    target_assignment: Some((selector, assignment)),
+                                }))
+                            }
+                            _ => unreachable!(),
+                        }
+                    }
+                    IndexingType::None => match variable_type.keyword {
+                        KeywordKind::Int => {
+                            Ok(VariableDeclaration::Score(ScoreVariableDeclaration {
+                                int_keyword: variable_type,
+                                criteria: criteria_selection,
+                                identifier,
+                                open_bracket,
+                                close_bracket,
+                                target_assignment: None,
+                            }))
+                        }
+                        KeywordKind::Bool => Ok(VariableDeclaration::Tag(TagVariableDeclaration {
+                            bool_keyword: variable_type,
+                            identifier,
+                            open_bracket,
+                            close_bracket,
+                            target_assignment: None,
+                        })),
+                        _ => unreachable!(),
+                    },
+                }
+            }
+            // SingleVariableDeclaration with Assignment
+            Reading::Atomic(Token::Punctuation(punc)) if punc.punctuation == '=' => {
+                self.forward();
+                let equals = punc;
+                let expression = self.parse_expression(handler)?;
+                let assignment = VariableDeclarationAssignment { equals, expression };
+
+                Ok(VariableDeclaration::Single(SingleVariableDeclaration {
+                    variable_type,
+                    identifier,
+                    assignment: Some(assignment),
+                }))
+            }
+            // SingleVariableDeclaration without Assignment
+            _ => Ok(VariableDeclaration::Single(SingleVariableDeclaration {
+                variable_type,
+                identifier,
+                assignment: None,
+            })),
         }
     }
 }

src/transpile/mod.rs

@@ -19,6 +19,8 @@ mod transpiler;
 #[cfg(feature = "shulkerbox")]
 #[cfg_attr(feature = "shulkerbox", doc(inline))]
 pub use transpiler::Transpiler;
+#[cfg(feature = "shulkerbox")]
+mod variables;
 
 pub mod util;
 

src/transpile/transpiler.rs

@@ -21,7 +21,7 @@ use crate::{
         program::{Namespace, ProgramFile},
         statement::{
             execute_block::{Conditional, Else, ExecuteBlock, ExecuteBlockHead, ExecuteBlockTail},
-            Statement,
+            SemicolonStatement, Statement,
         },
     },
     transpile::error::MissingFunctionDeclaration,
@@ -29,6 +29,7 @@ use crate::{
 
 use super::{
     error::{TranspileError, TranspileResult},
+    variables::{Scope, VariableType},
     FunctionData,
 };
 
@@ -74,8 +75,10 @@ impl Transpiler {
     ) -> Result<(), TranspileError> {
         tracing::trace!("Transpiling program declarations");
 
+        let scope = Scope::new();
+
         for program in programs {
-            self.transpile_program_declarations(program, handler);
+            self.transpile_program_declarations(program, &scope, handler);
         }
 
         let mut always_transpile_functions = Vec::new();
@@ -98,7 +101,7 @@ impl Transpiler {
         );
 
         for identifier_span in always_transpile_functions {
-            self.get_or_transpile_function(&identifier_span, None, handler)?;
+            self.get_or_transpile_function(&identifier_span, None, &scope, handler)?;
         }
 
         Ok(())
@@ -108,12 +111,13 @@ impl Transpiler {
     fn transpile_program_declarations(
         &mut self,
         program: &ProgramFile,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) {
         let namespace = program.namespace();
 
         for declaration in program.declarations() {
-            self.transpile_declaration(declaration, namespace, handler);
+            self.transpile_declaration(declaration, namespace, scope, handler);
         }
     }
 
@@ -123,6 +127,7 @@ impl Transpiler {
         &mut self,
         declaration: &Declaration,
         namespace: &Namespace,
+        _scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) {
         let program_identifier = declaration.span().source_file().identifier().clone();
@@ -143,7 +148,6 @@ impl Transpiler {
                         )
                     })
                     .collect();
-                #[allow(clippy::significant_drop_tightening)]
                 self.functions.insert(
                     (program_identifier, name),
                     FunctionData {
@@ -203,6 +207,7 @@ impl Transpiler {
                 if tag.replace().is_some() {
                     sb_tag.set_replace(true);
                 }
+                // TODO: handle global variables
             }
         };
     }
@@ -215,6 +220,7 @@ impl Transpiler {
         &mut self,
         identifier_span: &Span,
         arguments: Option<&[&Expression]>,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<(String, Option<BTreeMap<String, String>>)> {
         let program_identifier = identifier_span.source_file().identifier();
@@ -237,6 +243,8 @@ impl Transpiler {
         if !already_transpiled {
             tracing::trace!("Function not transpiled yet, transpiling.");
 
+            let function_scope = scope.new_child();
+
             let statements = {
                 let functions = &self.functions;
                 let function_data = functions
@@ -257,9 +265,15 @@ impl Transpiler {
                         error
                     })?;
 
+                for (i, param) in function_data.parameters.iter().enumerate() {
+                    function_scope.set_variable(param, VariableType::FunctionArgument { index: i });
+                }
+
                 function_data.statements.clone()
             };
-            let commands = self.transpile_function(&statements, program_identifier, handler)?;
+
+            let commands =
+                self.transpile_function(&statements, program_identifier, &function_scope, handler)?;
 
             let functions = &self.functions;
             let function_data = functions
@@ -369,22 +383,22 @@ impl Transpiler {
             })
             .map(|(s, _)| s.to_owned())?;
 
-        let arg_count = arguments.iter().flat_map(|x| x.iter()).count();
-        if arg_count != parameters.len() {
+        let arg_count = arguments.map(<[&Expression]>::len);
+        if arg_count.is_some_and(|arg_count| arg_count != parameters.len()) {
             let err = TranspileError::InvalidFunctionArguments(InvalidFunctionArguments {
                 expected: parameters.len(),
-                actual: arg_count,
+                actual: arg_count.expect("checked in if condition"),
                 span: identifier_span.clone(),
             });
             handler.receive(err.clone());
             Err(err)
-        } else if arg_count > 0 {
+        } else if arg_count.is_some_and(|arg_count| arg_count > 0) {
             let mut compiled_args = Vec::new();
             let mut errs = Vec::new();
             for expression in arguments.iter().flat_map(|x| x.iter()) {
                 let value = match expression {
                     Expression::Primary(Primary::FunctionCall(func)) => self
-                        .transpile_function_call(func, handler)
+                        .transpile_function_call(func, scope, handler)
                         .map(|cmd| match cmd {
                             Command::Raw(s) => s,
                             _ => unreachable!("Function call should always return a raw command"),
@@ -392,6 +406,8 @@ impl Transpiler {
                     Expression::Primary(Primary::Lua(lua)) => {
                         lua.eval_string(handler).map(Option::unwrap_or_default)
                     }
+                    Expression::Primary(Primary::Integer(num)) => Ok(num.span.str().to_string()),
+                    Expression::Primary(Primary::Boolean(bool)) => Ok(bool.span.str().to_string()),
                     Expression::Primary(Primary::StringLiteral(string)) => {
                         Ok(string.str_content().to_string())
                     }
@@ -424,13 +440,14 @@ impl Transpiler {
         &mut self,
         statements: &[Statement],
         program_identifier: &str,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Vec<Command>> {
         let mut errors = Vec::new();
         let commands = statements
             .iter()
             .filter_map(|statement| {
-                self.transpile_statement(statement, program_identifier, handler)
+                self.transpile_statement(statement, program_identifier, scope, handler)
                     .unwrap_or_else(|err| {
                         errors.push(err);
                         None
@@ -449,6 +466,7 @@ impl Transpiler {
         &mut self,
         statement: &Statement,
         program_identifier: &str,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Option<Command>> {
         match statement {
@@ -457,7 +475,21 @@ impl Transpiler {
             }
             Statement::Run(run) => match run.expression() {
                 Expression::Primary(Primary::FunctionCall(func)) => {
-                    self.transpile_function_call(func, handler).map(Some)
+                    self.transpile_function_call(func, scope, handler).map(Some)
+                }
+                Expression::Primary(Primary::Integer(num)) => {
+                    let error = TranspileError::UnexpectedExpression(UnexpectedExpression(
+                        Expression::Primary(Primary::Integer(num.clone())),
+                    ));
+                    handler.receive(error.clone());
+                    Err(error)
+                }
+                Expression::Primary(Primary::Boolean(bool)) => {
+                    let error = TranspileError::UnexpectedExpression(UnexpectedExpression(
+                        Expression::Primary(Primary::Boolean(bool.clone())),
+                    ));
+                    handler.receive(error.clone());
+                    Err(error)
                 }
                 Expression::Primary(Primary::StringLiteral(string)) => {
                     Ok(Some(Command::Raw(string.str_content().to_string())))
@@ -473,19 +505,26 @@ impl Transpiler {
                 unreachable!("Only literal commands are allowed in functions at this time.")
             }
             Statement::ExecuteBlock(execute) => {
-                self.transpile_execute_block(execute, program_identifier, handler)
+                let child_scope = scope.new_child();
+                self.transpile_execute_block(execute, program_identifier, &child_scope, handler)
             }
             Statement::DocComment(doccomment) => {
                 let content = doccomment.content();
                 Ok(Some(Command::Comment(content.to_string())))
             }
             Statement::Grouping(group) => {
+                let child_scope = scope.new_child();
                 let statements = group.block().statements();
                 let mut errors = Vec::new();
                 let commands = statements
                     .iter()
                     .filter_map(|statement| {
-                        self.transpile_statement(statement, program_identifier, handler)
+                        self.transpile_statement(
+                            statement,
+                            program_identifier,
+                            &child_scope,
+                            handler,
+                        )
                         .unwrap_or_else(|err| {
                             errors.push(err);
                             None
@@ -501,10 +540,11 @@ impl Transpiler {
                     Ok(Some(Command::Group(commands)))
                 }
             }
-            #[allow(clippy::match_wildcard_for_single_variants)]
-            Statement::Semicolon(semi) => match semi.expression() {
+            Statement::Semicolon(semi) => match semi.statement() {
+                #[expect(clippy::match_wildcard_for_single_variants)]
+                SemicolonStatement::Expression(expr) => match expr {
                     Expression::Primary(Primary::FunctionCall(func)) => {
-                    self.transpile_function_call(func, handler).map(Some)
+                        self.transpile_function_call(func, scope, handler).map(Some)
                     }
                     unexpected => {
                         let error = TranspileError::UnexpectedExpression(UnexpectedExpression(
@@ -514,20 +554,45 @@ impl Transpiler {
                         Err(error)
                     }
                 },
+                SemicolonStatement::VariableDeclaration(decl) => {
+                    // let value = match decl {
+                    //     VariableDeclaration::Single(single) => {
+                    //         match single.variable_type().keyword {
+                    //             KeywordKind::Int => {
+                    //                 VariableType::ScoreboardValue { objective: (), name: () }
+                    //             }
+                    //         }
+                    //     }
+                    // }
+                    // TODO: only for demonstration
+                    // scope.set_variable(
+                    //     decl.identifier().span.str(),
+                    //     VariableType::Tag {
+                    //         tag_name: "TODO".to_string(),
+                    //     },
+                    // );
+                    todo!("Variable declarations are not yet supported: {decl:?}")
+                }
+            },
         }
     }
 
     fn transpile_function_call(
         &mut self,
         func: &FunctionCall,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Command> {
         let arguments = func
             .arguments()
             .as_ref()
             .map(|l| l.elements().map(Deref::deref).collect::<Vec<_>>());
-        let (location, arguments) =
-            self.get_or_transpile_function(&func.identifier().span, arguments.as_deref(), handler)?;
+        let (location, arguments) = self.get_or_transpile_function(
+            &func.identifier().span,
+            arguments.as_deref(),
+            scope,
+            handler,
+        )?;
         let mut function_call = format!("function {location}");
         if let Some(arguments) = arguments {
             use std::fmt::Write;
@@ -551,9 +616,10 @@ impl Transpiler {
         &mut self,
         execute: &ExecuteBlock,
         program_identifier: &str,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Option<Command>> {
-        self.transpile_execute_block_internal(execute, program_identifier, handler)
+        self.transpile_execute_block_internal(execute, program_identifier, scope, handler)
             .map(|ex| ex.map(Command::Execute))
     }
 
@@ -561,6 +627,7 @@ impl Transpiler {
         &mut self,
         execute: &ExecuteBlock,
         program_identifier: &str,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Option<Execute>> {
         match execute {
@@ -572,7 +639,7 @@ impl Transpiler {
                             .statements()
                             .iter()
                             .filter_map(|s| {
-                                self.transpile_statement(s, program_identifier, handler)
+                                self.transpile_statement(s, program_identifier, scope, handler)
                                     .unwrap_or_else(|err| {
                                         errors.push(err);
                                         None
@@ -593,11 +660,12 @@ impl Transpiler {
                         .transpile_execute_block_internal(
                             execute_block,
                             program_identifier,
+                            scope,
                             handler,
                         ),
                 }?;
 
-                self.combine_execute_head_tail(head, tail, program_identifier, handler)
+                self.combine_execute_head_tail(head, tail, program_identifier, scope, handler)
             }
             ExecuteBlock::IfElse(cond, block, el) => {
                 let statements = block.statements();
@@ -608,7 +676,7 @@ impl Transpiler {
                     let commands = statements
                         .iter()
                         .filter_map(|statement| {
-                            self.transpile_statement(statement, program_identifier, handler)
+                            self.transpile_statement(statement, program_identifier, scope, handler)
                                 .unwrap_or_else(|err| {
                                     errors.push(err);
                                     None
@@ -620,7 +688,7 @@ impl Transpiler {
                     }
                     Some(Execute::Runs(commands))
                 } else {
-                    self.transpile_statement(&statements[0], program_identifier, handler)?
+                    self.transpile_statement(&statements[0], program_identifier, scope, handler)?
                         .map(|cmd| Execute::Run(Box::new(cmd)))
                 };
 
@@ -632,6 +700,7 @@ impl Transpiler {
                             then,
                             Some(el),
                             program_identifier,
+                            scope,
                             handler,
                         )
                     },
@@ -646,6 +715,7 @@ impl Transpiler {
         then: Execute,
         el: Option<&Else>,
         program_identifier: &str,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Option<Execute>> {
         let (_, cond) = cond.clone().dissolve();
@@ -659,7 +729,7 @@ impl Transpiler {
                 if statements.is_empty() {
                     None
                 } else if statements.len() == 1 {
-                    self.transpile_statement(&statements[0], program_identifier, handler)
+                    self.transpile_statement(&statements[0], program_identifier, scope, handler)
                         .unwrap_or_else(|err| {
                             errors.push(err);
                             None
@@ -669,7 +739,7 @@ impl Transpiler {
                     let commands = statements
                         .iter()
                         .filter_map(|statement| {
-                            self.transpile_statement(statement, program_identifier, handler)
+                            self.transpile_statement(statement, program_identifier, scope, handler)
                                 .unwrap_or_else(|err| {
                                     errors.push(err);
                                     None
@@ -697,12 +767,20 @@ impl Transpiler {
         head: &ExecuteBlockHead,
         tail: Option<Execute>,
         program_identifier: &str,
+        scope: &Scope,
         handler: &impl Handler<base::Error>,
     ) -> TranspileResult<Option<Execute>> {
         Ok(match head {
             ExecuteBlockHead::Conditional(cond) => {
                 if let Some(tail) = tail {
-                    self.transpile_conditional(cond, tail, None, program_identifier, handler)?
+                    self.transpile_conditional(
+                        cond,
+                        tail,
+                        None,
+                        program_identifier,
+                        scope,
+                        handler,
+                    )?
                 } else {
                     None
                 }

src/transpile/util.rs

@@ -47,11 +47,11 @@ pub fn identifier_to_macro(ident: &str) -> std::borrow::Cow<str> {
     if ident.contains("__")
         || ident
             .chars()
-            .any(|c| !(c == '_' && c.is_ascii_alphanumeric()))
+            .any(|c| c == '_' || !c.is_ascii_alphanumeric())
     {
         let new_ident = ident
             .chars()
-            .filter(|c| *c == '_' || c.is_ascii_alphanumeric())
+            .filter(|c| *c != '_' && c.is_ascii_alphanumeric())
             .collect::<String>();
 
         let chksum = md5::hash(ident).to_hex_lowercase();

src/transpile/variables.rs

@@ -0,0 +1,117 @@
+#![expect(unused)]
+
+use std::{collections::HashMap, sync::RwLock};
+
+use super::Transpiler;
+
+#[derive(Debug, Clone)]
+pub enum VariableType {
+    FunctionArgument {
+        index: usize,
+    },
+    Scoreboard {
+        objective: String,
+    },
+    ScoreboardValue {
+        objective: String,
+        name: String,
+    },
+    ScoreboardArray {
+        objective: String,
+        names: Vec<String>,
+    },
+    Tag {
+        tag_name: String,
+    },
+    BooleanStorage {
+        storage_name: String,
+        path: String,
+    },
+    BooleanStorageArray {
+        storage_name: String,
+        paths: Vec<String>,
+    },
+}
+
+#[derive(Debug, Default)]
+pub struct Scope<'a> {
+    parent: Option<&'a Scope<'a>>,
+    variables: RwLock<HashMap<String, VariableType>>,
+}
+
+impl<'a> Scope<'a> {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn new_child(&'a self) -> Self {
+        Self {
+            parent: Some(self),
+            variables: RwLock::new(HashMap::new()),
+        }
+    }
+
+    pub fn get_variable(&self, name: &str) -> Option<VariableType> {
+        let var = self.variables.read().unwrap().get(name).cloned();
+        if var.is_some() {
+            var
+        } else {
+            self.parent.and_then(|parent| parent.get_variable(name))
+        }
+    }
+
+    pub fn set_variable(&self, name: &str, var: VariableType) {
+        self.variables
+            .write()
+            .unwrap()
+            .insert(name.to_string(), var);
+    }
+
+    pub fn get_parent(&self) -> Option<&'a Self> {
+        self.parent
+    }
+}
+
+impl Transpiler {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_scope() {
+        let scope = Scope::new();
+        {
+            let mut variables = scope.variables.write().unwrap();
+            variables.insert(
+                "test".to_string(),
+                VariableType::Scoreboard {
+                    objective: "test".to_string(),
+                },
+            );
+        }
+        match scope.get_variable("test") {
+            Some(VariableType::Scoreboard { objective }) => assert_eq!(objective, "test"),
+            _ => panic!("Incorrect Variable"),
+        }
+    }
+
+    #[test]
+    fn test_parent() {
+        let scope = Scope::new();
+        {
+            let mut variables = scope.variables.write().unwrap();
+            variables.insert(
+                "test".to_string(),
+                VariableType::Scoreboard {
+                    objective: "test".to_string(),
+                },
+            );
+        }
+        let child = scope.new_child();
+        match child.get_variable("test") {
+            Some(VariableType::Scoreboard { objective }) => assert_eq!(objective, "test"),
+            _ => panic!("Incorrect Variable"),
+        }
+    }
+}