Remove union types

I will need to implement polymorphism later to allow for functions like `len` to work. Len currently relies on saying that its argument is either a list or a string, as strings are not a subtype of lists.

ppp_ast.py

@@ -1,6 +1,6 @@
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
-from typing import Dict, List, Optional, Tuple, Union
+from typing import Dict, List, Optional, Tuple
 
 ### Types ###
 
@@ -15,13 +15,6 @@ class TupleTypeExpr(TypeExpression):
 	def represent(self) -> str:
 		assert False, ("Unimplemented")
 
-@dataclass
-class UnionTypeExpr(TypeExpression):
-	types: List[TypeExpression]
-
-	def represent(self) -> str:
-		assert False, ("Unimplemented")
-
 @dataclass
 class ListTypeExpr(TypeExpression):
 	type: TypeExpression

ppp_interpreter.py

@@ -1,5 +1,5 @@
 from dataclasses import dataclass
-from typing import Dict, List as List_, Optional, Tuple, Union
+from typing import Dict, List as List_, Optional, Tuple
 
 from ppp_ast import *
 from ppp_lexer import Lexer
@@ -7,7 +7,7 @@ from ppp_object import Bool, EnumValue, Function, Int, Object, Str, Struct, Tupl
 from ppp_parser import is_valid_target, parse_statement
 from ppp_tokens import EofToken
 from ppp_stdlib import variables
-from ppp_types import EnumType, FunctionType, GenericType, Int as IntType, ListType, ReturnType, Str as StrType, StructType, TupleType, Type, TypeType, UnionType, VariableType, Void as VoidType
+from ppp_types import EnumType, FunctionType, GenericType, Int as IntType, ListType, ReturnType, Str as StrType, StructType, TupleType, Type, TypeType, VariableType, Void as VoidType
 
 @dataclass
 class Declared:
@@ -31,7 +31,7 @@ class Constant:
 	def from_obj(obj: Object) -> 'Declared':
 		return Declared(obj.get_type(), obj)
 
-VariableState = Union[Declared, Undeclared, Constant]
+VariableState = Declared | Undeclared | Constant
 
 Module = Dict[str, VariableState]
 
@@ -340,8 +340,6 @@ def calculate_type_expression(expression: TypeExpression, program: ProgramState,
 			return ListType(calculate_type_expression(type_, program, must_resolve))
 		case TupleTypeExpr(types_):
 			return TupleType([calculate_type_expression(type, program, must_resolve) for type in types_])
-		case UnionTypeExpr(types_):
-			return UnionType([calculate_type_expression(type, program, must_resolve) for type in types_])
 		case FunctionTypeExpr(arguments_, return_type_):
 			return FunctionType([calculate_type_expression(argument, program, must_resolve) for argument in arguments_], calculate_type_expression(return_type_, program, must_resolve))
 		case TypeSpecification(type_, types_):
@@ -413,7 +411,7 @@ class BreakResult:
 class NothingResult:
 	pass
 
-StatementsResult = Union[ReturnResult, ContinueResult, BreakResult, NothingResult]
+StatementsResult = ReturnResult | ContinueResult | BreakResult | NothingResult
 
 def interpret_statements(statements: List_[Statement], program: ProgramState) -> StatementsResult:
 	for statement in statements:

ppp_object.py

@@ -2,7 +2,7 @@
 
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
-from typing import Callable, Dict, List as List_, Tuple as Tuple_, Union as Union_
+from typing import Callable, Dict, List as List_, Tuple as Tuple_
 
 from ppp_ast import Statement
 from ppp_types import ArrayType, EnumType, FunctionType, ListType, ReturnType, StructType, TupleType, Type, Int as IntType, Str as StrType, Bool as BoolType, Void as VoidType, TypeType

ppp_parser.py

@@ -23,22 +23,11 @@ def parse_type_primary(lexer: Lexer) -> TypeExpression:
 	if lexer.take_token(SymbolToken(Symbol.Open)):
 		if lexer.take_token(SymbolToken(Symbol.Close)): return TupleTypeExpr([])
 
-		def parse_union(lexer: Lexer) -> TypeExpression:
-			union_types: List[TypeExpression] = [parse_type(lexer)]
-			while lexer.take_token(SymbolToken(Symbol.Pipe)):
-				union_types.append(parse_type(lexer))
-			if len(union_types) == 1:
-				return union_types[0]
-			return UnionTypeExpr(union_types)
-
-		types: List[TypeExpression] = [parse_union(lexer)]
+		types: List[TypeExpression] = [parse_type(lexer)]
 		while lexer.take_token(SymbolToken(Symbol.Comma)):
-			types.append(parse_union(lexer))
+			types.append(parse_type(lexer))
 		lexer.assert_token(SymbolToken(Symbol.Close))
-		if len(types) == 1 and isinstance(types[0], UnionTypeExpr):
-			base_type = types[0]
-		else:
-			base_type = TupleTypeExpr(types)
+		base_type = TupleTypeExpr(types)
 	elif lexer.take_token(SymbolToken(Symbol.OpenSquare)):
 		type = parse_type(lexer)
 		lexer.assert_token(SymbolToken(Symbol.CloseSquare))

ppp_stdlib.py

@@ -2,7 +2,7 @@ from typing import Callable, Dict, List, Tuple
 
 from ppp_ast import Statements
 from ppp_object import Bool, EnumValue, Int, Object, Function, Str, TypeObject, Void, List as ListObject
-from ppp_types import Bool as BoolType, FunctionType, GenericType, Int as IntType, Str as StrType, Type, TypeType, VariableType, Void as VoidType, Object as ObjectType, UnionType, ListType
+from ppp_types import Bool as BoolType, FunctionType, GenericType, Int as IntType, Str as StrType, Type, TypeType, VariableType, Void as VoidType, Object as ObjectType, ListType
 
 
 def PythonFunction(name: str, parameters: List[Tuple[str, Type]], return_type: Type, func: Callable[..., Object]) -> Object:
@@ -41,7 +41,8 @@ def len_impl(list_: Object) -> Object:
 		case _: assert False, ("Unimplemented", list_)
 	assert False
 
-Len = PythonFunction("len", [('list', UnionType([ListType(VariableType("")), StrType]))], IntType, len_impl)
+# TODO: Use polymorphism to make this work for both list<T> and str
+# Len = PythonFunction("len", [('list', UnionType([ListType(VariableType("")), StrType]))], IntType, len_impl)
 
 def str_to_int_impl(str_: Object) -> Object:
 	assert isinstance(str_, Str)
@@ -99,7 +100,7 @@ variables: Dict[str, Object] = {
 	'void': VoidTypeObj,
 	'debug_print': DebugPrint,
 	'read': Read,
-	'len': Len,
+	# 'len': Len,
 	'str_to_int': StrToInt,
 	'none': NoneObj,
 	'range': Range,

ppp_tokens.py

@@ -1,7 +1,5 @@
 from dataclasses import dataclass
 from enum import Enum
-from typing import List, Literal, Tuple, Union
-
 
 class Keyword(Enum):
 	Enum = 'enum'
@@ -88,14 +86,7 @@ class SymbolToken:
 @dataclass
 class EofToken: pass
 
-TokenContents = Union[
-	KeywordToken,
-	IdentifierToken,
-	NumberToken,
-	StringToken,
-	SymbolToken,
-	EofToken
-]
+TokenContents = KeywordToken | IdentifierToken | NumberToken | StringToken | SymbolToken | EofToken
 
 @dataclass
 class Token:

ppp_types.py

@@ -1,7 +1,7 @@
 
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
-from typing import Dict, List, Tuple, Union
+from typing import Dict, List, Tuple
 
 import sys
 sys.setrecursionlimit(1000)
@@ -40,10 +40,6 @@ class Type(ABC):
 			case VariableType(self_name), VariableType(other_name):
 				return self_name == other_name
 			case _, VariableType(""): return True
-			case type, UnionType(types):
-				for union_type in types:
-					if type.is_subtype_of(union_type): return True
-				return False
 			case BoolType(), BoolType(): return True
 			case type, ObjectType(): return True
 			case type_a, type_b if type_a.__class__ != type_b.__class__: return False
@@ -164,21 +160,6 @@ class FunctionType(Type):
 		is_new_return_type, new_return_type = self.return_type.new_fill(types, stack+[id(self)])
 		return (is_new_arguments or is_new_return_type, FunctionType(new_arguments, new_return_type))
 
-@dataclass
-class UnionType(Type):
-	types: List[Type]
-
-	def fill(self, types: Dict[str, Type], stack: List[int]) -> Type:
-		if id(self) in stack: return self
-		self.types = [type.fill(types, stack+[id(self)]) for type in self.types]
-		return self
-
-	def new_fill(self, types: Dict[str, Type], stack: List[int]) -> Tuple[bool, Type]:
-		is_new, new_types = self.new_fill_list(self.types, types, stack)
-		return (is_new, UnionType(new_types))
-
-	def represent(self) -> str: return '('+'|'.join([type.represent() for type in self.types])+')'
-
 class ObjectType(Primitive):
 	def represent(self) -> str: return 'object'
 Object = ObjectType()