closes #18 implement type aliases

src/frontend/ast.rs

@@ -152,6 +152,11 @@ pub enum Statement {
         generics: Vec<Type>,// TODO: add generics
         fields: Vec<(String, Type)>,
     },
+    AliasDecl {
+        name: String,
+        generics: Vec<Type>,
+        ty: Type,
+    },
 }
 
 impl Statement {
@@ -196,6 +201,10 @@ impl Statement {
     pub fn new_record_decl(name: String, generics: Vec<Type>, fields: Vec<(String, Type)>, line: usize) -> Located<Self> {
         Located::new(Self::RecordDecl { name, generics, fields }, line)
     }
+
+    pub fn new_alias_decl(name: String, generics: Vec<Type>, ty: Type, line: usize) -> Located<Self> {
+        Located::new(Self::AliasDecl { name, generics, ty }, line)
+    }
 }
 
 pub type Block = Vec<Located<Statement>>;

src/frontend/parser.rs

@@ -490,6 +490,7 @@ fn statement<'a>(parser: &mut Parser<'a>) -> Option<Located<Statement>> {
         TokenKind::LeftBrace => block_statement(parser),
         TokenKind::Return => return_statement(parser),
         TokenKind::Record => record_declaration(parser),
+        TokenKind::Type => alias_declaration(parser),
         _ => expression_statement(parser),
     }
 }
@@ -644,7 +645,24 @@ fn record_declaration<'a>(parser: &mut Parser<'a>) -> Option<Located<Statement>>
     let name = parser.previous.lexeme.to_string();
     let fields = parse_record_fields(parser)?;
     // TODO: add generic handling
-    Some(Statement::new_record_decl(name, vec![], fields, line))
+    let generics = vec![];
+    Some(Statement::new_record_decl(name, generics, fields, line))
+}
+
+fn alias_declaration<'a>(parser: &mut Parser<'a>) -> Option<Located<Statement>> {
+    // advance over the alias keyword
+    advance(parser);
+    // advance over the identifier
+    advance(parser);
+    let line = parser.previous.line;
+    let name = parser.previous.lexeme.to_string();
+    // TODO: handle generics
+    let generics = vec![];
+    // expect an equals sign
+    consume(parser, TokenKind::Eq, "Expected an equals sign after alias declaration.")?;
+    // parse the type
+    let ty = type_expr(parser)?;
+    Some(Statement::new_alias_decl(name, generics, ty, line))
 }
 
 // top level parsing =====
@@ -1003,5 +1021,22 @@ mod tests {
             ],
         });
     }
+
+    #[test]
+    fn test_alias_declaration() {
+        let scanner = Scanner::new("type Vec = [f32; 10]");
+        let mut parser = Parser::new(scanner);
+        let stmt = statement(&mut parser);
+        assert!(stmt.is_some());
+        let alias_decl = stmt.unwrap().node;
+        assert_eq!(alias_decl, Statement::AliasDecl { 
+            name: "Vec".to_string(),
+            generics: vec![],
+            ty: Type::Array {
+                element_type: Box::new(Type::F32),
+                size: 10,
+            },
+        });
+    }
 }
 

src/frontend/scanner.rs

@@ -46,6 +46,7 @@ pub enum TokenKind {
     Break,
     Continue,
     Record,
+    Type,
     // Literals
     Number,
     String,
@@ -103,6 +104,7 @@ impl Display for TokenKind {
             TokenKind::Break => write!(f, "break"),
             TokenKind::Continue => write!(f, "continue"),
             TokenKind::Record => write!(f, "record"),
+            TokenKind::Type => write!(f, "type"),
             TokenKind::Number => write!(f, "<number>"),
             TokenKind::String => write!(f, "<string>"),
             TokenKind::Char => write!(f, "<char>"),
@@ -215,6 +217,7 @@ impl<'a> Scanner<'a> {
             "break" => TokenKind::Break,
             "continue" => TokenKind::Continue,
             "record" => TokenKind::Record,
+            "type" => TokenKind::Type,
             _ => TokenKind::Identifier,
         };
 

src/frontend/types.rs

@@ -32,14 +32,6 @@ pub enum Type {
     }
 }
 
-#[derive(Debug, PartialEq, Clone)]
-pub struct Record {
-    pub name: String,
-    // type vars
-    pub generics: Vec<Type>,
-    pub fields: Vec<(String, Type)>,
-}
-
 impl Display for Type {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
@@ -83,14 +75,45 @@ impl Display for Type {
     }
 }
 
+#[derive(Debug, PartialEq, Clone)]
+pub enum Udt {
+    Record {
+        name: String,
+        generics: Vec<Type>,
+        fields: Vec<(String, Type)>,
+    },
+    Alias {
+        name: String,
+        generics: Vec<Type>,
+        ty: Type,
+    }
+}
+
+impl Udt {
+    pub fn new_record(name: String, generics: Vec<Type>, fields: Vec<(String, Type)>) -> Self {
+        Self::Record { name, generics, fields }
+    }
+
+    pub fn new_alias(name: String, generics: Vec<Type>, ty: Type) -> Self {
+        Self::Alias { name, generics, ty }
+    }
+
+    pub fn name(&self) -> &str {
+        match self {
+            Udt::Record { name, .. } => name,
+            Udt::Alias { name, .. } => name,
+        }
+    }
+}
+
 type FnSig = (Vec<Type>, Type);
 
 #[derive(Clone)]
 pub struct TypeEnv {
     pub fn_sig: Option<FnSig>,
     parent: Option<Rc<RefCell<TypeEnv>>>,
     bindings: HashMap<String, Type>,
-    record_types: HashMap<String, Record>,
+    udts: HashMap<String, Udt>,
 }
 
 impl TypeEnv {
@@ -100,7 +123,7 @@ impl TypeEnv {
             fn_sig: None,
             parent: None,
             bindings: HashMap::new(),
-            record_types: HashMap::new(),
+            udts: HashMap::new(),
         }
     }
 
@@ -110,7 +133,7 @@ impl TypeEnv {
             fn_sig: None,
             parent: Some(Rc::new(RefCell::new(self.clone()))),
             bindings: HashMap::new(),
-            record_types: HashMap::new(),
+            udts: HashMap::new(),
         }
     }
 
@@ -120,7 +143,7 @@ impl TypeEnv {
             fn_sig: Some((params, return_type)),
             parent: Some(Rc::new(RefCell::new(self.clone()))),
             bindings: HashMap::new(),
-            record_types: HashMap::new(),
+            udts: HashMap::new(),
         }
     }
 
@@ -131,8 +154,8 @@ impl TypeEnv {
             .or_else(|| self.parent.as_ref().and_then(|p| p.borrow().get(ident)))
     }
 
-    pub fn get_record(&self, ident: &str) -> Option<Record> {
-        self.record_types.get(ident).cloned()
+    pub fn get_udt(&self, ident: &str) -> Option<Udt> {
+        self.udts.get(ident).cloned()
     }
 
     /// inserts a type into the top level type environment
@@ -144,16 +167,16 @@ impl TypeEnv {
         }
     }
 
-    pub fn insert_record_top(&mut self, record: Record) -> Result<(), String> {
+    pub fn insert_udt_top(&mut self, udt: Udt) -> Result<(), String> {
         if self.parent.is_none() {
             // ensure that the record name is not already in the type env
-            if self.record_types.contains_key(&record.name) {
-                return Err(format!("Record {} already exists in the type environment", record.name));
+            if self.udts.contains_key(udt.name()) {
+                return Err(format!("UDT {} already exists in the type environment", udt.name()));
             }
-            self.record_types.insert(record.name.clone(), record);
+            self.udts.insert(udt.name().to_string(), udt);
             Ok(())
         } else {
-            self.parent.as_ref().unwrap().borrow_mut().insert_record_top(record)
+            self.parent.as_ref().unwrap().borrow_mut().insert_udt_top(udt)
         }
     }
 

src/passes/type_pass.rs

@@ -1,4 +1,4 @@
-use crate::{Block, Expression, Program, Record, Statement, TokenKind, Type, TypeEnv};
+use crate::{Block, Expression, Program, Statement, TokenKind, Type, TypeEnv, Udt};
 
 // TODO: add handling for type var identifiers in expressions such as let x: TypeVar = 1; then x is a type var and let y = x + 1; will need resolution
 // TODO: add handling for function calls in which the the callee has type vars in its signature
@@ -13,7 +13,10 @@ fn add_udt_pass(program: &Program, type_env: &mut TypeEnv) -> Result<Program, St
     for stmt in program.statements.iter() {
         match &stmt.node {
             Statement::RecordDecl { name, fields, generics } => {
-                type_env.insert_record_top(Record { name: name.clone(), generics: generics.clone(), fields: fields.clone() })?;
+                type_env.insert_udt_top(Udt::Record { name: name.clone(), generics: generics.clone(), fields: fields.clone() })?;
+            }
+            Statement::AliasDecl { name, generics, ty } => {
+                type_env.insert_udt_top(Udt::Alias { name: name.clone(), generics: generics.clone(), ty: ty.clone() })?;
             }
             _ => new_program.add_statement(stmt.clone()),
         }
@@ -406,6 +409,22 @@ mod tests {
         env
     }
 
+    #[test]
+    fn test_alias_declaration() {
+        let mut program = Program::new();
+        program.add_statement(Statement::new_alias_decl("Vec".to_string(), vec![], Type::Array { element_type: Box::new(Type::I64), size: 10 }, 1));
+        let new_env = type_check_program(&program).unwrap();
+        assert_eq!(new_env.get_udt("Vec"), Some(Udt::Alias { name: "Vec".to_string(), generics: vec![], ty: Type::Array { element_type: Box::new(Type::I64), size: 10 } }));
+    }
+
+    #[test]
+    fn test_record_declaration() {
+        let mut program = Program::new();
+        program.add_statement(Statement::new_record_decl("Point".to_string(), vec![], vec![("x".to_string(), Type::I64), ("y".to_string(), Type::I64)], 1));
+        let new_env = type_check_program(&program).unwrap();
+        assert_eq!(new_env.get_udt("Point"), Some(Udt::Record { name: "Point".to_string(), generics: vec![], fields: vec![("x".to_string(), Type::I64), ("y".to_string(), Type::I64)] }));
+    }
+
     #[test]
     fn test_literal_types() {
         let mut env = create_test_env();