Merge pull request 'Improve syntax and types' (#5) from feat/improve-syntax-and-types into feat/basic-type-checker

Reviewed-on: #5

examples/00_syntax_prototype/02_custom_types.py

@@ -2,10 +2,6 @@
 # ruff: disable[F821]
 from __future__ import annotations
 
-# Prototype of custom type import to use valid Python syntax
-import midas
-midas.using("02_custom_types.midas")
-
 # A data-frame using a custom type
 df: Frame[
     location: GeoLocation

examples/00_syntax_prototype/05_custom_types_v3.midas

@@ -0,0 +1,33 @@
+type Foo1 = float
+type Foo2 = float where (_ > 3)
+type Foo3 = int | float
+type Foo4 = int where (_ > 3) | float where (_ > 3)
+type Foo5 = (int | float) where (_ > 3)
+type Foo6 = {
+    foo: float
+    bar: float where (_ > 3)
+}
+
+type Foo7[T] = T where (_ > 3)
+type Foo8[A, B<:int] = {
+    a: A
+    b: B
+}
+
+type Complex = {
+    a: int
+    b: int
+}
+type Complex2 = Complex where (_.a > 3 & _.b < 5)
+
+predicate Positive(n: int) = n >= 0
+
+extend Foo1 {
+    op __add__(Foo1) -> Foo1
+}
+
+extend Foo7[T] {
+    op __add__(Foo7[T]) -> Foo7[T]
+}
+
+type Optional[T] = None | T

examples/01_simple_type_checking/02_simple_types.midas

@@ -1,6 +1,6 @@
-type Meter(float)
+type Meter = float
-type Second(float)
+type Second = float
-type MeterPerSecond(float)
+type MeterPerSecond = float
 
 extend Meter {
     op __add__(Meter) -> Meter

examples/01_simple_type_checking/02_simple_types.py

@@ -1,8 +1,6 @@
 # type: ignore
 # ruff: disable [F821]
 
-midas.using("02_simple_types.midas")
-
 distance: Meter = cast(Meter, 123.45)
 time: Second = cast(Second, 6.7)
 speed = distance / time

examples/01_simple_type_checking/03_control_flow.py

@@ -4,13 +4,20 @@ def minimum(x: int, y: int):
     else:
         return y
 
+
 a = 15
 b = 72
 c = minimum(a, b)
 
+
 def factorial(n: int) -> int:
     if n <= 1:
         return 1
     return n * factorial(n - 1)
 
-category = "Category 1" if a < 10 else "Category 2"
+
+category = "Category 1" if a < 10 else "Category 2"
+
+
+def foo() -> None:
+    pass

gen/midas.py

@@ -13,40 +13,38 @@ from midas.lexer.token import Token
 
 
 ###> Stmt | Statements
-class SimpleTypeStmt:
+class TypeStmt:
     name: Token
-    template: Optional[TemplateExpr]
+    params: list[Param]
-    base: TypeExpr
+    type: Type
-    constraint: Optional[Expr]
 
-
+    @dataclass(frozen=True, kw_only=True)
-class ComplexTypeStmt:
+    class Param:
-    name: Token
+        location: Location
-    template: Optional[TemplateExpr]
+        name: Token
-    properties: list[PropertyStmt]
+        bound: Optional[Type]
 
 
 class PropertyStmt:
     name: Token
-    type: TypeExpr
+    type: Type
-    constraint: Optional[Expr]
 
 
 class ExtendStmt:
-    type: TypeExpr
+    type: Type
     operations: list[OpStmt]
 
 
 class OpStmt:
     name: Token
-    operand: TypeExpr
+    operand: Type
-    result: TypeExpr
+    result: Type
 
 
 class PredicateStmt:
     name: Token
     subject: Token
-    type: TypeExpr
+    type: Type
     condition: Expr
 
 
@@ -54,9 +52,6 @@ class PredicateStmt:
 
 
 ###> Expr | Expressions
-class SimpleTypeExpr:
-    name: Token
-    optional: bool
 
 
 class LogicalExpr:
@@ -97,14 +92,27 @@ class WildcardExpr:
     token: Token
 
 
-class TemplateExpr:
+###<
-    type: TypeExpr
+
+###> Type | Types
 
 
-class TypeExpr:
+class NamedType:
     name: Token
-    template: Optional[TemplateExpr]
+
-    optional: bool
+
+class GenericType:
+    type: Type
+    params: list[Type]
+
+
+class ConstraintType:
+    type: Type
+    constraint: Expr
+
+
+class ComplexType:
+    properties: list[PropertyStmt]
 
 
 ###<

midas/ast/midas.py

@@ -28,10 +28,7 @@ class Stmt(ABC):
 
     class Visitor(ABC, Generic[T]):
         @abstractmethod
-        def visit_simple_type_stmt(self, stmt: SimpleTypeStmt) -> T: ...
+        def visit_type_stmt(self, stmt: TypeStmt) -> T: ...
-
-        @abstractmethod
-        def visit_complex_type_stmt(self, stmt: ComplexTypeStmt) -> T: ...
 
         @abstractmethod
         def visit_property_stmt(self, stmt: PropertyStmt) -> T: ...
@@ -47,31 +44,25 @@ class Stmt(ABC):
 
 
 @dataclass(frozen=True)
-class SimpleTypeStmt(Stmt):
+class TypeStmt(Stmt):
     name: Token
-    template: Optional[TemplateExpr]
+    params: list[Param]
-    base: TypeExpr
+    type: Type
-    constraint: Optional[Expr]
+
+    @dataclass(frozen=True, kw_only=True)
+    class Param:
+        location: Location
+        name: Token
+        bound: Optional[Type]
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
-        return visitor.visit_simple_type_stmt(self)
+        return visitor.visit_type_stmt(self)
-
-
-@dataclass(frozen=True)
-class ComplexTypeStmt(Stmt):
-    name: Token
-    template: Optional[TemplateExpr]
-    properties: list[PropertyStmt]
-
-    def accept(self, visitor: Stmt.Visitor[T]) -> T:
-        return visitor.visit_complex_type_stmt(self)
 
 
 @dataclass(frozen=True)
 class PropertyStmt(Stmt):
     name: Token
-    type: TypeExpr
+    type: Type
-    constraint: Optional[Expr]
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
         return visitor.visit_property_stmt(self)
@@ -79,7 +70,7 @@ class PropertyStmt(Stmt):
 
 @dataclass(frozen=True)
 class ExtendStmt(Stmt):
-    type: TypeExpr
+    type: Type
     operations: list[OpStmt]
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
@@ -89,8 +80,8 @@ class ExtendStmt(Stmt):
 @dataclass(frozen=True)
 class OpStmt(Stmt):
     name: Token
-    operand: TypeExpr
+    operand: Type
-    result: TypeExpr
+    result: Type
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
         return visitor.visit_op_stmt(self)
@@ -100,7 +91,7 @@ class OpStmt(Stmt):
 class PredicateStmt(Stmt):
     name: Token
     subject: Token
-    type: TypeExpr
+    type: Type
     condition: Expr
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
@@ -120,9 +111,6 @@ class Expr(ABC):
     def accept(self, visitor: Visitor[T]) -> T: ...
 
     class Visitor(ABC, Generic[T]):
-        @abstractmethod
-        def visit_simple_type_expr(self, expr: SimpleTypeExpr) -> T: ...
-
         @abstractmethod
         def visit_logical_expr(self, expr: LogicalExpr) -> T: ...
 
@@ -147,21 +135,6 @@ class Expr(ABC):
         @abstractmethod
         def visit_wildcard_expr(self, expr: WildcardExpr) -> T: ...
 
-        @abstractmethod
-        def visit_template_expr(self, expr: TemplateExpr) -> T: ...
-
-        @abstractmethod
-        def visit_type_expr(self, expr: TypeExpr) -> T: ...
-
-
-@dataclass(frozen=True)
-class SimpleTypeExpr(Expr):
-    name: Token
-    optional: bool
-
-    def accept(self, visitor: Expr.Visitor[T]) -> T:
-        return visitor.visit_simple_type_expr(self)
-
 
 @dataclass(frozen=True)
 class LogicalExpr(Expr):
@@ -233,19 +206,61 @@ class WildcardExpr(Expr):
         return visitor.visit_wildcard_expr(self)
 
 
-@dataclass(frozen=True)
+#########
-class TemplateExpr(Expr):
+# Types #
-    type: TypeExpr
+#########
 
-    def accept(self, visitor: Expr.Visitor[T]) -> T:
+
-        return visitor.visit_template_expr(self)
+@dataclass(frozen=True, kw_only=True)
+class Type(ABC):
+    location: Location
+
+    @abstractmethod
+    def accept(self, visitor: Visitor[T]) -> T: ...
+
+    class Visitor(ABC, Generic[T]):
+        @abstractmethod
+        def visit_named_type(self, type: NamedType) -> T: ...
+
+        @abstractmethod
+        def visit_generic_type(self, type: GenericType) -> T: ...
+
+        @abstractmethod
+        def visit_constraint_type(self, type: ConstraintType) -> T: ...
+
+        @abstractmethod
+        def visit_complex_type(self, type: ComplexType) -> T: ...
 
 
 @dataclass(frozen=True)
-class TypeExpr(Expr):
+class NamedType(Type):
     name: Token
-    template: Optional[TemplateExpr]
-    optional: bool
 
-    def accept(self, visitor: Expr.Visitor[T]) -> T:
+    def accept(self, visitor: Type.Visitor[T]) -> T:
-        return visitor.visit_type_expr(self)
+        return visitor.visit_named_type(self)
+
+
+@dataclass(frozen=True)
+class GenericType(Type):
+    type: Type
+    params: list[Type]
+
+    def accept(self, visitor: Type.Visitor[T]) -> T:
+        return visitor.visit_generic_type(self)
+
+
+@dataclass(frozen=True)
+class ConstraintType(Type):
+    type: Type
+    constraint: Expr
+
+    def accept(self, visitor: Type.Visitor[T]) -> T:
+        return visitor.visit_constraint_type(self)
+
+
+@dataclass(frozen=True)
+class ComplexType(Type):
+    properties: list[PropertyStmt]
+
+    def accept(self, visitor: Type.Visitor[T]) -> T:
+        return visitor.visit_complex_type(self)

midas/ast/printer.py

@@ -85,40 +85,39 @@ class AstPrinter(Generic[T]):
                 child.accept(self)
 
 
-class MidasAstPrinter(AstPrinter, m.Expr.Visitor[None], m.Stmt.Visitor[None]):
+class MidasAstPrinter(
+    AstPrinter, m.Expr.Visitor[None], m.Stmt.Visitor[None], m.Type.Visitor[None]
+):
     # Statements
 
-    def visit_simple_type_stmt(self, stmt: m.SimpleTypeStmt):
+    def visit_type_stmt(self, stmt: m.TypeStmt) -> None:
-        self._write_line("SimpleTypeStmt")
+        self._write_line("TypeStmt")
         with self._child_level():
             self._write_line(f'name: "{stmt.name.lexeme}"')
-            self._write_optional_child("template", stmt.template)
+            self._write_line("params")
-            self._write_line("base")
-            with self._child_level(single=True):
-                stmt.base.accept(self)
-            self._write_optional_child("constraint", stmt.constraint, last=True)
-
-    def visit_complex_type_stmt(self, stmt: m.ComplexTypeStmt):
-        self._write_line("ComplexTypeStmt")
-        with self._child_level():
-            self._write_line(f'name: "{stmt.name.lexeme}"')
-            self._write_optional_child("template", stmt.template)
-            self._write_line("properties", last=True)
             with self._child_level():
-                for i, prop in enumerate(stmt.properties):
+                for i, param in enumerate(stmt.params):
                     self._idx = i
-                    if i == len(stmt.properties) - 1:
+                    if i == len(stmt.params) - 1:
                         self._mark_last()
-                    prop.accept(self)
+                    self._print_type_stmt_param(param)
+            self._write_line("type", last=True)
+            with self._child_level(single=True):
+                stmt.type.accept(self)
+
+    def _print_type_stmt_param(self, param: m.TypeStmt.Param) -> None:
+        self._write_line("Param")
+        with self._child_level():
+            self._write_line(f'name: "{param.name.lexeme}"')
+            self._write_optional_child("bound", param.bound, last=True)
 
     def visit_property_stmt(self, stmt: m.PropertyStmt):
         self._write_line("PropertyStmt")
         with self._child_level():
             self._write_line(f'name: "{stmt.name.lexeme}"')
-            self._write_line("type")
+            self._write_line("type", last=True)
             with self._child_level(single=True):
                 stmt.type.accept(self)
-            self._write_optional_child("constraint", stmt.constraint, last=True)
 
     def visit_extend_stmt(self, stmt: m.ExtendStmt) -> None:
         self._write_line("ExtendStmt")
@@ -161,12 +160,6 @@ class MidasAstPrinter(AstPrinter, m.Expr.Visitor[None], m.Stmt.Visitor[None]):
 
     # Expressions
 
-    def visit_simple_type_expr(self, expr: m.SimpleTypeExpr):
-        self._write_line("SimpleTypeExpr")
-        with self._child_level():
-            self._write_line(f'name: "{expr.name.lexeme}"')
-            self._write_line(f"optional: {expr.optional}", last=True)
-
     def visit_logical_expr(self, expr: m.LogicalExpr):
         self._write_line("LogicalExpr")
         with self._child_level():
@@ -230,22 +223,48 @@ class MidasAstPrinter(AstPrinter, m.Expr.Visitor[None], m.Stmt.Visitor[None]):
     def visit_wildcard_expr(self, expr: m.WildcardExpr) -> None:
         self._write_line("WildcardExpr")
 
-    def visit_template_expr(self, expr: m.TemplateExpr) -> None:
+    def visit_named_type(self, type: m.NamedType) -> None:
-        self._write_line("TemplateExpr")
+        self._write_line("NamedType")
-        with self._child_level(single=True):
+        with self._child_level():
+            self._write_line(f'name: "{type.name.lexeme}"', last=True)
+
+    def visit_generic_type(self, type: m.GenericType) -> None:
+        self._write_line("GenericType")
+        with self._child_level():
+            self._write_line("type")
+            with self._child_level():
+                type.type.accept(self)
+            self._write_line("params", last=True)
+            with self._child_level():
+                for i, param in enumerate(type.params):
+                    self._idx = i
+                    if i == len(type.params) - 1:
+                        self._mark_last()
+                    param.accept(self)
+
+    def visit_constraint_type(self, type: m.ConstraintType) -> None:
+        self._write_line("ConstraintType")
+        with self._child_level():
             self._write_line("type")
             with self._child_level(single=True):
-                expr.type.accept(self)
+                type.type.accept(self)
+            self._write_line("constraint", last=True)
+            with self._child_level(single=True):
+                type.constraint.accept(self)
 
-    def visit_type_expr(self, expr: m.TypeExpr):
+    def visit_complex_type(self, type: m.ComplexType) -> None:
-        self._write_line("TypeExpr")
+        self._write_line("ComplexType")
         with self._child_level():
-            self._write_line(f'name: "{expr.name.lexeme}"')
+            self._write_line("properties", last=True)
-            self._write_optional_child("template", expr.template)
+            with self._child_level():
-            self._write_line(f"optional: {expr.optional}", last=True)
+                for i, prop in enumerate(type.properties):
+                    self._idx = i
+                    if i == len(type.properties) - 1:
+                        self._mark_last()
+                    prop.accept(self)
 
 
-class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str]):
+class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str], m.Type.Visitor[str]):
     def __init__(self, indent: int = 4):
         self.indent: int = indent
         self.level: int = 0
@@ -253,33 +272,28 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str]):
     def indented(self, text: str) -> str:
         return " " * (self.level * self.indent) + text
 
-    def print(self, expr: m.Expr | m.Stmt):
+    def print(self, expr: m.Expr | m.Stmt | m.Type) -> str:
         self.level = 0
         return expr.accept(self)
 
-    def visit_simple_type_stmt(self, stmt: m.SimpleTypeStmt):
+    def visit_type_stmt(self, stmt: m.TypeStmt) -> str:
-        template: str = stmt.template.accept(self) if stmt.template is not None else ""
+        template: str = ""
-        res: str = f"type {stmt.name.lexeme}{template}({stmt.base.accept(self)})"
+        if len(stmt.params) != 0:
-        if stmt.constraint is not None:
+            params: list[str] = [
-            res += " where " + stmt.constraint.accept(self)
+                self._print_type_template_param(param) for param in stmt.params
+            ]
+            template = f"[{', '.join(params)}]"
+        res: str = f"type {stmt.name.lexeme}{template} = {stmt.type.accept(self)}"
         return self.indented(res)
 
-    def visit_complex_type_stmt(self, stmt: m.ComplexTypeStmt):
+    def _print_type_template_param(self, param: m.TypeStmt.Param) -> str:
-        template: str = stmt.template.accept(self) if stmt.template is not None else ""
+        res: str = param.name.lexeme
-        res: str = self.indented(f"type {stmt.name.lexeme}{template}")
+        if param.bound is not None:
-        res += " {\n"
+            res += "<:" + param.bound.accept(self)
-        self.level += 1
-        for prop in stmt.properties:
-            res += prop.accept(self)
-            res += "\n"
-        self.level -= 1
-        res += self.indented("}")
         return res
 
     def visit_property_stmt(self, stmt: m.PropertyStmt):
         res: str = f"{stmt.name.lexeme}: {stmt.type.accept(self)}"
-        if stmt.constraint is not None:
-            res += " where " + stmt.constraint.accept(self)
         return self.indented(res)
 
     def visit_extend_stmt(self, stmt: m.ExtendStmt):
@@ -289,13 +303,13 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str]):
         for op in stmt.operations:
             res += op.accept(self)
         self.level -= 1
-        res += "\n" + self.indented("}")
+        res += self.indented("}")
         return res
 
     def visit_op_stmt(self, stmt: m.OpStmt):
         operand: str = stmt.operand.accept(self)
         result: str = stmt.result.accept(self)
-        return self.indented(f"op {stmt.name.lexeme}({operand}) -> {result}")
+        return self.indented(f"op {stmt.name.lexeme}({operand}) -> {result}\n")
 
     def visit_predicate_stmt(self, stmt: m.PredicateStmt):
         name: str = stmt.name.lexeme
@@ -304,9 +318,6 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str]):
         condition: str = stmt.condition.accept(self)
         return self.indented(f"predicate {name}({subject}: {type}) = {condition}")
 
-    def visit_simple_type_expr(self, expr: m.SimpleTypeExpr):
-        return f"{expr.name.lexeme}{'?' if expr.optional else ''}"
-
     def visit_logical_expr(self, expr: m.LogicalExpr):
         left: str = expr.left.accept(self)
         operator: str = expr.operator.lexeme
@@ -342,12 +353,30 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str]):
     def visit_wildcard_expr(self, expr: m.WildcardExpr):
         return "_"
 
-    def visit_template_expr(self, expr: m.TemplateExpr):
+    def visit_named_type(self, type: m.NamedType) -> str:
-        return f"[{expr.type.accept(self)}]"
+        return type.name.lexeme
 
-    def visit_type_expr(self, expr: m.TypeExpr):
+    def visit_generic_type(self, type: m.GenericType) -> str:
-        template: str = expr.template.accept(self) if expr.template is not None else ""
+        res: str = type.type.accept(self)
-        return f"{expr.name.lexeme}{template}{'?' if expr.optional else ''}"
+        if len(type.params) != 0:
+            params: list[str] = [param.accept(self) for param in type.params]
+            res += f"[{', '.join(params)}]"
+        return res
+
+    def visit_constraint_type(self, type: m.ConstraintType) -> str:
+        res: str = type.type.accept(self)
+        res += " where " + type.constraint.accept(self)
+        return res
+
+    def visit_complex_type(self, type: m.ComplexType) -> str:
+        res: str = "{\n"
+        self.level += 1
+        for prop in type.properties:
+            res += prop.accept(self)
+            res += "\n"
+        self.level -= 1
+        res += self.indented("}")
+        return res
 
 
 class PythonAstPrinter(
@@ -600,11 +629,11 @@ class PythonAstPrinter(
             self._write_line("test")
             with self._child_level(single=True):
                 expr.test.accept(self)
-            
+
             self._write_line("if_true")
             with self._child_level(single=True):
                 expr.if_true.accept(self)
-            
+
             self._write_line("if_false", last=True)
             with self._child_level(single=True):
                 expr.if_false.accept(self)

midas/checker/checker.py

@@ -9,7 +9,7 @@ from midas.ast.location import Location
 from midas.checker.diagnostic import Diagnostic, DiagnosticType
 from midas.checker.environment import Environment
 from midas.checker.operators import COMPARATOR_METHODS, OPERATOR_METHODS
-from midas.checker.types import BaseType, Function, SimpleType, Type, UnitType, UnknownType
+from midas.checker.types import Function, Type, UnitType, UnknownType
 from midas.lexer.midas import MidasLexer
 from midas.lexer.token import Token
 from midas.parser.midas import MidasParser
@@ -34,9 +34,15 @@ class Checker(
 ):
     """A type checker which can use custom type definitions"""
 
-    def __init__(self, locals: dict[p.Expr, int], file_path: Path):
+    def __init__(
+        self,
+        locals: dict[p.Expr, int],
+        source_path: Path,
+        types_paths: list[Path],
+    ):
         self.logger: logging.Logger = logging.getLogger("Checker")
-        self.file_path: Path = file_path
+        self.source_path: Path = source_path
+        self.types_paths: list[Path] = types_paths
         self.ctx: MidasResolver = MidasResolver()
         self.global_env: Environment = Environment()
         self.env: Environment = self.global_env
@@ -46,7 +52,7 @@ class Checker(
     def diagnostic(self, type: DiagnosticType, location: Location, message: str):
         self.diagnostics.append(
             Diagnostic(
-                file_path=self.file_path,
+                file_path=self.source_path,
                 location=location,
                 type=type,
                 message=message,
@@ -74,7 +80,7 @@ class Checker(
             message=message,
         )
 
-    def evaluate(self, expr: p.Expr) -> Type:
+    def type_of(self, expr: p.Expr) -> Type:
         """Evaluate the type of an expression
 
         Args:
@@ -85,13 +91,13 @@ class Checker(
         """
         return expr.accept(self)
 
-    def evaluate_block(self, block: list[p.Stmt], env: Environment) -> bool:
+    def process_block(self, block: list[p.Stmt], env: Environment) -> bool:
         """Evaluate a sequence of statements
 
         Args:
             block (list[p.Stmt]): the statements to evaluate
             env (Environment): the environment in which to evaluate
-        
+
         Returns:
             bool: whether a return statement is present in the block
         """
@@ -119,6 +125,12 @@ class Checker(
             list[Diagnostic]: the list of diagnostics (errors, warning, etc.)
         """
         self.diagnostics = []
+
+        for path in self.types_paths:
+            self.import_midas(path)
+        self.logger.debug(f"Midas types: {self.ctx._types}")
+        self.logger.debug(f"Midas operations: {self.ctx._operations}")
+
         for stmt in statements:
             stmt.accept(self)
 
@@ -140,30 +152,6 @@ class Checker(
             return self.env.get_at(distance, name)
         return self.global_env.get(name)
 
-    def parse_midas_import(self, expr: p.CallExpr) -> Optional[Path]:
-        """Parse a Midas import statement
-
-        The statement should be written as `midas.using("path/to/types.midas")`
-
-        Args:
-            expr (p.CallExpr): the import call expression
-
-        Returns:
-            Optional[Path]: the path to the imported file, or None if the expression is malformed
-        """
-        match expr:
-            case p.CallExpr(
-                callee=p.GetExpr(
-                    object=p.VariableExpr(name="midas"),
-                    name="using",
-                ),
-                arguments=[
-                    p.LiteralExpr(value=path),
-                ],
-            ):
-                return Path(path)
-        return None
-
     def import_midas(self, path: Path) -> None:
         """Import Midas definitions from a path
 
@@ -171,17 +159,14 @@ class Checker(
             path (Path): the import path
         """
         self.logger.debug(f"Importing type definitions from {path}")
-        path = (self.file_path.parent / path).resolve()
         lexer: MidasLexer = MidasLexer(path.read_text())
         tokens: list[Token] = lexer.process()
         parser: MidasParser = MidasParser(tokens)
         stmts: list[m.Stmt] = parser.parse()
         self.ctx.resolve(stmts)
-        self.logger.debug(f"Midas types: {self.ctx._types}")
-        self.logger.debug(f"Midas operations: {self.ctx._operations}")
 
     def visit_expression_stmt(self, stmt: p.ExpressionStmt) -> None:
-        self.evaluate(stmt.expr)
+        self.type_of(stmt.expr)
 
     def visit_function(self, stmt: p.Function) -> None:
         env: Environment = Environment(self.env)
@@ -223,7 +208,7 @@ class Checker(
 
         for arg in pos_args + args + kw_args:
             env.define(arg.name, arg.type)
-        
+
         returns_hint: Optional[Type] = None
         if stmt.returns is not None:
             returns_hint = stmt.returns.accept(self)
@@ -237,7 +222,7 @@ class Checker(
             )
             self.env.define(stmt.name, inside_function)
 
-        returned: bool = self.evaluate_block(stmt.body, env)
+        returned: bool = self.process_block(stmt.body, env)
         inferred_return: Type = UnknownType()
         if not returned:
             env.return_types.append(UnitType())
@@ -278,7 +263,7 @@ class Checker(
         self.env.define(stmt.name, type)
 
     def visit_assign_stmt(self, stmt: p.AssignStmt) -> None:
-        value: Type = self.evaluate(stmt.value)
+        value: Type = self.type_of(stmt.value)
         for target in stmt.targets:
             if not isinstance(target, p.VariableExpr):
                 self.logger.warning(f"Unsupported assignment to {target}")
@@ -317,8 +302,8 @@ class Checker(
             )
 
         env: Environment = Environment(self.env)
-        body_returned: bool = self.evaluate_block(stmt.body, env)
+        body_returned: bool = self.process_block(stmt.body, env)
-        else_returned: bool = self.evaluate_block(stmt.orelse, env)
+        else_returned: bool = self.process_block(stmt.orelse, env)
         self.env.return_types.extend(env.return_types)
         if body_returned and else_returned:
             raise ReturnException()
@@ -329,8 +314,8 @@ class Checker(
             self.logger.warning(f"Unsupported operator {expr.operator}")
             self.warning(expr.location, f"Unsupported operator {expr.operator}")
             return UnknownType()
-        left: Type = self.evaluate(expr.left)
+        left: Type = self.type_of(expr.left)
-        right: Type = self.evaluate(expr.right)
+        right: Type = self.type_of(expr.right)
 
         result: Optional[Type] = self.ctx.get_operation_result(left, method, right)
         if result is None:
@@ -347,8 +332,8 @@ class Checker(
             self.logger.warning(f"Unsupported operator {expr.operator}")
             self.warning(expr.location, f"Unsupported operator {expr.operator}")
             return UnknownType()
-        left: Type = self.evaluate(expr.left)
+        left: Type = self.type_of(expr.left)
-        right: Type = self.evaluate(expr.right)
+        right: Type = self.type_of(expr.right)
 
         result: Optional[Type] = self.ctx.get_operation_result(left, method, right)
         if result is None:
@@ -362,10 +347,7 @@ class Checker(
     def visit_unary_expr(self, expr: p.UnaryExpr) -> Type: ...
 
     def visit_call_expr(self, expr: p.CallExpr) -> Type:
-        if path := self.parse_midas_import(expr):
+        callee: Type = self.type_of(expr.callee)
-            self.import_midas(path)
-            return UnknownType()
-        callee: Type = self.evaluate(expr.callee)
         if not isinstance(callee, Function):
             self.error(expr.callee.location, "Callee is not a function")
             return UnknownType()
@@ -398,7 +380,16 @@ class Checker(
     def visit_variable_expr(self, expr: p.VariableExpr) -> Type:
         return self.look_up_variable(expr.name, expr) or UnknownType()
 
-    def visit_logical_expr(self, expr: p.LogicalExpr) -> Type: ...
+    def visit_logical_expr(self, expr: p.LogicalExpr) -> Type:
+        left: Type = expr.left.accept(self)
+        right: Type = expr.right.accept(self)
+        # TODO: union type
+        if left != right:
+            self.error(
+                expr.location,
+                f"Operands must be of the same type, left={left} != right={right}",
+            )
+        return left
 
     def visit_set_expr(self, expr: p.SetExpr) -> Type: ...
 
@@ -417,7 +408,10 @@ class Checker(
         true_type: Type = expr.if_true.accept(self)
         false_type: Type = expr.if_false.accept(self)
         if true_type != false_type:
-            self.error(expr.location, f"Type mismatch in ternary if branches: true={true_type} != false={false_type}")
+            self.error(
+                expr.location,
+                f"Type mismatch in ternary if branches: true={true_type} != false={false_type}",
+            )
             return UnknownType()
         return true_type
 
@@ -448,10 +442,10 @@ class Checker(
             list[MappedArgument]: the list of mapped arguments
         """
         positional: list[tuple[p.Expr, Type]] = [
-            (arg, self.evaluate(arg)) for arg in call.arguments
+            (arg, self.type_of(arg)) for arg in call.arguments
         ]
         keywords: dict[str, tuple[p.Expr, Type]] = {
-            name: (arg, self.evaluate(arg)) for name, arg in call.keywords.items()
+            name: (arg, self.type_of(arg)) for name, arg in call.keywords.items()
         }
         set_args: set[str] = set()
 

midas/checker/types.py

@@ -9,9 +9,9 @@ class BaseType:
 
 
 @dataclass(frozen=True, kw_only=True)
-class SimpleType:
+class AliasType:
     name: str
-    base: BaseType | SimpleType
+    type: Type
 
 
 @dataclass(frozen=True, kw_only=True)
@@ -39,4 +39,9 @@ class Function:
         required: bool
 
 
-Type = BaseType | SimpleType | UnknownType | UnitType | Function
+@dataclass(frozen=True, kw_only=True)
+class ComplexType:
+    properties: dict[str, Type]
+
+
+Type = BaseType | AliasType | UnknownType | UnitType | Function | ComplexType

midas/cli/highlight.css

@@ -53,5 +53,6 @@ span {
 
     &.keyword {
         color: rgb(211, 72, 9);
+        pointer-events: none;
     }
 }

midas/cli/highlighter.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
+from dataclasses import dataclass
 from pathlib import Path
 from typing import Generic, Optional, Protocol, TextIO, TypeVar
 
@@ -8,6 +9,7 @@ import midas.ast.midas as m
 import midas.ast.python as p
 from midas.ast.location import Location
 from midas.checker.diagnostic import Diagnostic
+from midas.lexer.token import Token
 
 H = TypeVar("H", bound="Highlighter", contravariant=True)
 
@@ -22,6 +24,15 @@ class Locatable(Protocol):
     def location(self) -> Optional[Location]: ...
 
 
+@dataclass(frozen=True)
+class LocatableToken:
+    token: Token
+
+    @property
+    def location(self) -> Location:
+        return self.token.get_location()
+
+
 class Highlighter(ABC):
     BASE_CSS_PATH: Path = Path(__file__).parent / "highlight.css"
     EXTRA_CSS_PATH: Optional[Path] = None
@@ -206,34 +217,22 @@ class PythonHighlighter(
     def visit_ternary_expr(self, expr: p.TernaryExpr) -> None: ...
 
 
-class MidasHighlighter(Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None]):
+class MidasHighlighter(
+    Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[None]
+):
     EXTRA_CSS_PATH: Optional[Path] = Path(__file__).parent / "hl_midas.css"
 
     def highlight(self, node: Highlightable[MidasHighlighter]):
         node.accept(self)
 
-    def visit_simple_type_stmt(self, stmt: m.SimpleTypeStmt) -> None:
+    def visit_type_stmt(self, stmt: m.TypeStmt) -> None:
-        self.wrap(stmt, "simple-type")
+        self.wrap(stmt, "type-stmt")
-        if stmt.template is not None:
+        self.wrap(LocatableToken(stmt.name), "type-name")
-            stmt.template.accept(self)
+        stmt.type.accept(self)
-        stmt.base.accept(self)
-        if stmt.constraint is not None:
-            self.wrap(stmt.constraint, "constraint")
-            stmt.constraint.accept(self)
-
-    def visit_complex_type_stmt(self, stmt: m.ComplexTypeStmt) -> None:
-        self.wrap(stmt, "complex-type")
-        if stmt.template is not None:
-            stmt.template.accept(self)
-        for prop in stmt.properties:
-            prop.accept(self)
 
     def visit_property_stmt(self, stmt: m.PropertyStmt) -> None:
         self.wrap(stmt, "property")
         stmt.type.accept(self)
-        if stmt.constraint is not None:
-            self.wrap(stmt.constraint, "constraint")
-            stmt.constraint.accept(self)
 
     def visit_extend_stmt(self, stmt: m.ExtendStmt) -> None:
         self.wrap(stmt, "extend")
@@ -243,17 +242,16 @@ class MidasHighlighter(Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None]):
 
     def visit_op_stmt(self, stmt: m.OpStmt) -> None:
         self.wrap(stmt, "op")
+        self.wrap(LocatableToken(stmt.name), "op-name")
         stmt.operand.accept(self)
         stmt.result.accept(self)
 
     def visit_predicate_stmt(self, stmt: m.PredicateStmt) -> None:
         self.wrap(stmt, "predicate")
+        self.wrap(LocatableToken(stmt.name), "predicate-name")
         stmt.type.accept(self)
         stmt.condition.accept(self)
 
-    def visit_simple_type_expr(self, expr: m.SimpleTypeExpr) -> None:
-        self.wrap(expr, "simple-type-expr")
-
     def visit_logical_expr(self, expr: m.LogicalExpr) -> None:
         self.wrap(expr, "logical-expr")
         expr.left.accept(self)
@@ -282,14 +280,24 @@ class MidasHighlighter(Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None]):
 
     def visit_wildcard_expr(self, expr: m.WildcardExpr) -> None: ...
 
-    def visit_template_expr(self, expr: m.TemplateExpr) -> None:
+    def visit_named_type(self, type: m.NamedType) -> None:
-        self.wrap(expr, "template")
+        self.wrap(type, "named-type")
-        expr.type.accept(self)
 
-    def visit_type_expr(self, expr: m.TypeExpr) -> None:
+    def visit_generic_type(self, type: m.GenericType) -> None:
-        self.wrap(expr, "type")
+        self.wrap(type, "generic-type")
-        if expr.template is not None:
+        type.type.accept(self)
-            expr.template.accept(self)
+        for param in type.params:
+            param.accept(self)
+
+    def visit_constraint_type(self, type: m.ConstraintType) -> None:
+        self.wrap(type, "constraint-type")
+        type.type.accept(self)
+        type.constraint.accept(self)
+
+    def visit_complex_type(self, type: m.ComplexType) -> None:
+        self.wrap(type, "complex-type")
+        for prop in type.properties:
+            prop.accept(self)
 
 
 class DiagnosticsHighlighter(Highlighter):

midas/cli/hl_midas.css

@@ -5,12 +5,11 @@ span {
         font-style: italic;
     }
 
-    &.simple-type {
+    &.named-type,
-        --col: 108, 233, 108;
+    &.generic-type,
-    }
+    &.constraint-type,
-
     &.complex-type {
-        --col: 233, 206, 108;
+        --col: 150, 150, 150;
     }
 
     &.constraint {
@@ -33,10 +32,6 @@ span {
         --col: 193, 108, 233;
     }
 
-    &.simple-type-expr {
-        --col: 150, 150, 150;
-    }
-
     &.logical-expr,
     &.binary-expr,
     &.unary-expr,
@@ -48,7 +43,9 @@ span {
         --col: 163, 117, 71;
     }
 
-    &.type {
+    &.type-name,
+    &.op-name,
+    &.predicate-name {
         --col: 200, 200, 200;
         font-weight: bold;
     }

midas/cli/main.py

@@ -1,7 +1,6 @@
 import ast
 import json
 import logging
-from dataclasses import dataclass
 from pathlib import Path
 from typing import Optional, TextIO, get_args
 
@@ -9,14 +8,14 @@ import click
 
 import midas.ast.midas as m
 import midas.ast.python as p
-from midas.ast.location import Location
+from midas.ast.printer import MidasAstPrinter, MidasPrinter, PythonAstPrinter
-from midas.ast.printer import MidasAstPrinter, PythonAstPrinter
 from midas.checker.checker import Checker
 from midas.checker.diagnostic import Diagnostic
 from midas.checker.types import Type
 from midas.cli.highlighter import (
     DiagnosticsHighlighter,
     Highlighter,
+    LocatableToken,
     MidasHighlighter,
     PythonHighlighter,
 )
@@ -35,8 +34,9 @@ def midas():
 
 @midas.command()
 @click.option("-l", "--highlight", type=click.File("w"))
+@click.option("-t", "--types", type=click.File("r"), multiple=True)
 @click.argument("file", type=click.File("r"))
-def compile(highlight: Optional[TextIO], file: TextIO):
+def compile(highlight: Optional[TextIO], file: TextIO, types: tuple[TextIO]):
     logging.basicConfig(level=logging.DEBUG)
     source: str = file.read()
     tree: ast.Module = ast.parse(source, filename=file.name)
@@ -44,7 +44,12 @@ def compile(highlight: Optional[TextIO], file: TextIO):
     stmts: list[p.Stmt] = parser.parse_module(tree)
     resolver = Resolver()
     resolver.resolve(*stmts)
-    checker = Checker(resolver.locals, file_path=Path(file.name).resolve())
+    types_paths: list[Path] = [Path(t.name).resolve() for t in types]
+    checker = Checker(
+        resolver.locals,
+        source_path=Path(file.name).resolve(),
+        types_paths=types_paths,
+    )
     diagnostics: list[Diagnostic] = checker.check(stmts)
     for diagnostic in diagnostics:
         print(diagnostic)
@@ -142,14 +147,6 @@ def highlight_midas(source: str, path: str) -> Highlighter:
     for err in parser.errors:
         print(err.get_report())
 
-    @dataclass(frozen=True)
-    class LocatableToken:
-        token: Token
-
-        @property
-        def location(self) -> Location:
-            return self.token.get_location()
-
     for stmt in stmts:
         highlighter.highlight(stmt)
     for token in tokens:
@@ -176,5 +173,21 @@ def highlight(output: TextIO, file: TextIO):
     highlighter.dump(output)
 
 
+@midas.command()
+@click.option("-o", "--output", type=click.File("w"), default="-")
+@click.argument("file", type=click.File("r"))
+def format(output: TextIO, file: TextIO):
+    source: str = file.read()
+    printer = MidasPrinter()
+    lexer = MidasLexer(source, file=file.name)
+    tokens: list[Token] = lexer.process()
+    parser = MidasParser(tokens)
+    stmts: list[m.Stmt] = parser.parse()
+    for err in parser.errors:
+        print(err.get_report())
+    for stmt in stmts:
+        output.write(printer.print(stmt) + "\n")
+
+
 if __name__ == "__main__":
     midas()

midas/lexer/midas.py

@@ -40,8 +40,8 @@ class MidasLexer(Lexer):
                 self.add_token(TokenType.AND)
             case "?":
                 self.add_token(TokenType.QMARK)
-            # case ",":
+            case ",":
-            #     self.add_token(TokenType.COMMA)
+                self.add_token(TokenType.COMMA)
             case "_" if not self.is_identifier_char(self.peek_next(), start=False):
                 self.add_token(TokenType.UNDERSCORE)
             case "-" if self.match(">"):

midas/lexer/token.py

@@ -17,7 +17,7 @@ class TokenType(Enum):
     LEFT_BRACE = auto()
     RIGHT_BRACE = auto()
     COLON = auto()
-    # COMMA = auto()
+    COMMA = auto()
     UNDERSCORE = auto()
     ARROW = auto()
     AND = auto()

midas/parser/midas.py

@@ -3,21 +3,22 @@ from typing import Optional
 from midas.ast.location import Location
 from midas.ast.midas import (
     BinaryExpr,
-    ComplexTypeStmt,
+    ComplexType,
+    ConstraintType,
     Expr,
     ExtendStmt,
+    GenericType,
     GetExpr,
     GroupingExpr,
     LiteralExpr,
     LogicalExpr,
+    NamedType,
     OpStmt,
     PredicateStmt,
     PropertyStmt,
-    SimpleTypeExpr,
-    SimpleTypeStmt,
     Stmt,
-    TemplateExpr,
+    Type,
-    TypeExpr,
+    TypeStmt,
     UnaryExpr,
     VariableExpr,
     WildcardExpr,
@@ -81,7 +82,7 @@ class MidasParser(Parser):
             self.synchronize()
             return None
 
-    def type_declaration(self) -> SimpleTypeStmt | ComplexTypeStmt:
+    def type_declaration(self) -> TypeStmt:
         """Parse a type declaration
 
         A type declaration can either be a simple type alias or a new complex type.
@@ -107,33 +108,22 @@ class MidasParser(Parser):
         """
         keyword: Token = self.previous()
         name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
-        template: Optional[TemplateExpr] = None
+        params: list[TypeStmt.Param] = []
         if self.check(TokenType.LEFT_BRACKET):
-            template = self.template_expr()
+            params = self.type_stmt_params()
 
-        if self.match(TokenType.LEFT_PAREN):
+        self.consume(TokenType.EQUAL, "Expected '=' before type definition")
-            base: TypeExpr = self.type_expr()
-            self.consume(TokenType.RIGHT_PAREN, "Unclosed base type parenthesis")
-            constraint: Optional[Expr] = None
-            if self.match(TokenType.WHERE):
-                constraint = self.constraint()
-            return SimpleTypeStmt(
-                location=keyword.location_to(self.previous()),
-                name=name,
-                template=template,
-                base=base,
-                constraint=constraint,
-            )
-        else:
-            properties: list[PropertyStmt] = self.type_properties()
-            return ComplexTypeStmt(
-                location=keyword.location_to(self.previous()),
-                name=name,
-                template=template,
-                properties=properties,
-            )
 
-    def template_expr(self) -> TemplateExpr:
+        type: Type = self.type_expr()
+
+        return TypeStmt(
+            location=keyword.location_to(self.previous()),
+            name=name,
+            params=params,
+            type=type,
+        )
+
+    def type_stmt_params(self) -> list[TypeStmt.Param]:
         """Parse a generic template expression
 
         A template is written `[TypeExpr]`
@@ -141,16 +131,27 @@ class MidasParser(Parser):
         Returns:
             TemplateExpr: the parsed template expression
         """
-        left: Token = self.consume(
+        self.consume(TokenType.LEFT_BRACKET, "Missing '[' before template expression")
-            TokenType.LEFT_BRACKET, "Missing '[' before template expression"
+        params: list[TypeStmt.Param] = []
-        )
+        while not self.is_at_end() and not self.check(TokenType.RIGHT_BRACKET):
-        type: TypeExpr = self.type_expr()
+            name: Token = self.consume(TokenType.IDENTIFIER, "Expected type variable")
-        right: Token = self.consume(
+            bound: Optional[Type] = None
-            TokenType.RIGHT_BRACKET, "Missing ']' after template expression"
+            if self.match(TokenType.LESS):
-        )
+                self.consume(TokenType.COLON, "Expected ':' after '<'")
-        return TemplateExpr(location=left.location_to(right), type=type)
+                bound = self.type_expr()
+            params.append(
+                TypeStmt.Param(
+                    location=name.location_to(self.previous()),
+                    name=name,
+                    bound=bound,
+                )
+            )
+            if not self.match(TokenType.COMMA):
+                break
+        self.consume(TokenType.RIGHT_BRACKET, "Missing ']' after template expression")
+        return params
 
-    def type_expr(self) -> TypeExpr:
+    def type_expr(self) -> Type:
         """Parse a type expression
 
         A type is an identifier, optionally followed by a template expression.
@@ -159,30 +160,82 @@ class MidasParser(Parser):
         Returns:
             TypeExpr: the parsed type expression
         """
-        name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
+        return self.constraint_type()
-        template: Optional[TemplateExpr] = None
+
+    def constraint_type(self) -> Type:
+        type: Type = self.base_type()
+        if self.match(TokenType.WHERE):
+            constraint: Expr = self.constraint()
+            return ConstraintType(
+                location=Location.span(type.location, constraint.location),
+                type=type,
+                constraint=constraint,
+            )
+        return type
+
+    def base_type(self) -> Type:
+        if self.match(TokenType.LEFT_PAREN):
+            type: Type = self.type_expr()
+            self.consume(TokenType.RIGHT_PAREN, "Unclosed parenthesis")
+            return type
+
+        if self.check(TokenType.LEFT_BRACE):
+            return self.complex_type()
+
+        return self.generic_type()
+
+    def generic_type(self) -> Type:
+        type: Type = self.named_type()
         if self.check(TokenType.LEFT_BRACKET):
-            template = self.template_expr()
+            params: list[Type] = self.type_params()
-        optional: bool = self.match(TokenType.QMARK)
+            return GenericType(
-        return TypeExpr(
+                location=Location.span(type.location, self.previous().get_location()),
-            location=name.location_to(self.previous()),
+                type=type,
+                params=params,
+            )
+        return type
+
+    def type_params(self) -> list[Type]:
+        params: list[Type] = []
+        self.consume(TokenType.LEFT_BRACKET, "Missing '[' before generic parameters")
+        while not self.is_at_end() and not self.check(TokenType.RIGHT_BRACKET):
+            params.append(self.type_expr())
+            if not self.match(TokenType.COMMA):
+                break
+        self.consume(TokenType.RIGHT_BRACKET, "Missing ']' after generic parameters")
+        return params
+
+    def named_type(self) -> Type:
+        name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
+        return NamedType(
+            location=name.get_location(),
             name=name,
-            template=template,
-            optional=optional,
         )
 
-    def simple_type_expr(self) -> SimpleTypeExpr:
+    def complex_type(self) -> Type:
-        """Parse a simple type expression
+        """Parse a type definition body
 
-        A simple type is just an identifier optionally followed by a '?'
+        A type definition body is a set of whitespace-separated
+        property statements enclosed in curly braces
 
         Returns:
-            SimpleTypeExpr: the parsed simple type expression
+            list[PropertyStmt]: the parsed type properties
         """
-        name: Token = self.consume(TokenType.IDENTIFIER, "Expected type name")
+        left: Token = self.consume(
-        optional: bool = self.match(TokenType.QMARK)
+            TokenType.LEFT_BRACE, "Expected '{' to start type body"
-        return SimpleTypeExpr(
+        )
-            location=name.location_to(self.previous()), name=name, optional=optional
+        properties: list[PropertyStmt] = []
+        names: set[str] = set()
+        while not self.check(TokenType.RIGHT_BRACE) and not self.is_at_end():
+            prop: PropertyStmt = self.property_stmt()
+            if prop.name.lexeme in names:
+                raise self.error(prop.name, "Duplicate property")
+            names.add(prop.name.lexeme)
+            properties.append(prop)
+        right: Token = self.consume(TokenType.RIGHT_BRACE, "Unclosed type body")
+        return ComplexType(
+            location=left.location_to(right),
+            properties=properties,
         )
 
     def constraint(self) -> Expr:
@@ -308,27 +361,6 @@ class MidasParser(Parser):
 
         raise self.error(self.peek(), "Expected expression")
 
-    def type_properties(self) -> list[PropertyStmt]:
-        """Parse a type definition body
-
-        A type definition body is a set of whitespace-separated
-        property statements enclosed in curly braces
-
-        Returns:
-            list[PropertyStmt]: the parsed type properties
-        """
-        self.consume(TokenType.LEFT_BRACE, "Expected '{' to start type body")
-        properties: list[PropertyStmt] = []
-        names: set[str] = set()
-        while not self.check(TokenType.RIGHT_BRACE) and not self.is_at_end():
-            prop: PropertyStmt = self.property_stmt()
-            if prop.name.lexeme in names:
-                raise self.error(prop.name, "Duplicate property")
-            names.add(prop.name.lexeme)
-            properties.append(prop)
-        self.consume(TokenType.RIGHT_BRACE, "Unclosed type body")
-        return properties
-
     def property_stmt(self) -> PropertyStmt:
         """Parse a property statement
 
@@ -339,15 +371,11 @@ class MidasParser(Parser):
         """
         name: Token = self.consume(TokenType.IDENTIFIER, "Expected property name")
         self.consume(TokenType.COLON, "Expected ':' after property name")
-        type: TypeExpr = self.type_expr()
+        type: Type = self.type_expr()
-        constraint: Optional[Expr] = None
-        if self.match(TokenType.WHERE):
-            constraint = self.constraint()
         return PropertyStmt(
             location=name.location_to(self.previous()),
             name=name,
             type=type,
-            constraint=constraint,
         )
 
     def extend_declaration(self) -> ExtendStmt:
@@ -359,7 +387,7 @@ class MidasParser(Parser):
             ExtendStmt: the parsed extension statement
         """
         keyword: Token = self.previous()
-        type: TypeExpr = self.type_expr()
+        type: Type = self.type_expr()
         self.consume(TokenType.LEFT_BRACE, "Expected '{' to start extend body")
         operations: list[OpStmt] = []
         while not self.is_at_end() and not self.check(TokenType.RIGHT_BRACE):
@@ -380,11 +408,11 @@ class MidasParser(Parser):
 
         name: Token = self.consume(TokenType.IDENTIFIER, "Expected operation name")
         self.consume(TokenType.LEFT_PAREN, "Expected '(' before operand type")
-        operand: TypeExpr = self.type_expr()
+        operand: Type = self.type_expr()
         self.consume(TokenType.RIGHT_PAREN, "Expected ')' after operand type")
 
         self.consume(TokenType.ARROW, "Expected '->' before result type")
-        result: TypeExpr = self.type_expr()
+        result: Type = self.type_expr()
 
         return OpStmt(
             location=keyword.location_to(self.previous()),
@@ -406,7 +434,7 @@ class MidasParser(Parser):
         self.consume(TokenType.LEFT_PAREN, "Expected '(' before predicate subject")
         subject: Token = self.consume(TokenType.IDENTIFIER, "Expected subject name")
         self.consume(TokenType.COLON, "Expected ':' after subject name")
-        type: TypeExpr = self.type_expr()
+        type: Type = self.type_expr()
         self.consume(TokenType.RIGHT_PAREN, "Expected ')' after predicate subject")
         self.consume(TokenType.EQUAL, "Expected '=' after predicate subject")
         condition: Expr = self.constraint()

midas/parser/python.py

@@ -87,6 +87,9 @@ class PythonParser:
             case ast.If():
                 return self.parse_if(node)
 
+            case ast.Pass():
+                return None
+
             case _:
                 print(f"Unsupported statement: {ast.unparse(node)}")
                 return None
@@ -311,6 +314,13 @@ class PythonParser:
                             constraint=right_expr,
                         )
 
+            case ast.Constant(value=None):
+                return BaseType(
+                    location=loc,
+                    base="None",
+                    param=None,
+                )
+
             case _:
                 raise UnsupportedSyntaxError(type_expr)
 

midas/resolver/builtin.py

@@ -16,6 +16,7 @@ def op(ctx: MidasResolver, t1: Type, operator: str, t2: Type, t3: Type):
         result=t3,
     )
 
+
 def basic_op(ctx: MidasResolver, type: Type, op: str):
     ctx.define_operation(
         left=type,
@@ -68,4 +69,4 @@ def define_builtins(ctx: MidasResolver):
     op(ctx, float, "__gt__", int, bool)  # float > int = bool
     op(ctx, float, "__le__", int, bool)  # float <= int = bool
     op(ctx, float, "__ge__", int, bool)  # float >= int = bool
-    op(ctx, float, "__eq__", int, bool)  # float == int = bool
+    op(ctx, float, "__eq__", int, bool)  # float == int = bool

midas/resolver/midas.py

@@ -1,11 +1,15 @@
 from typing import Optional
 
 import midas.ast.midas as m
-from midas.checker.types import BaseType, SimpleType, Type
+from midas.checker.types import (
+    AliasType,
+    Type,
+    UnknownType,
+)
 from midas.resolver.builtin import define_builtins
 
 
-class MidasResolver(m.Stmt.Visitor[None], m.Expr.Visitor[Type]):
+class MidasResolver(m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[Type]):
     """A resolver which evaluates Midas type definitions and build a registry"""
 
     def __init__(self) -> None:
@@ -94,20 +98,13 @@ class MidasResolver(m.Stmt.Visitor[None], m.Expr.Visitor[Type]):
         for stmt in stmts:
             stmt.accept(self)
 
-    def visit_simple_type_stmt(self, stmt: m.SimpleTypeStmt) -> None:
+    def visit_type_stmt(self, stmt: m.TypeStmt) -> None:
-        # TODO generics, optional, constraint
+        type: Type = stmt.type.accept(self)
-        base: Type = self.get_type(stmt.base.name.lexeme)
+        for param in stmt.params:
-        match base:
+            if param.bound is not None:
-            case BaseType() | SimpleType():
+                param.bound.accept(self)
-                type = SimpleType(
+        name: str = stmt.name.lexeme
-                    name=stmt.name.lexeme,
+        self.define_type(name, AliasType(name=name, type=type))
-                    base=base,
-                )
-                self.define_type(type.name, type)
-            case _:
-                raise TypeError(f"Invalid base {base} for simple type")
-
-    def visit_complex_type_stmt(self, stmt: m.ComplexTypeStmt) -> None: ...
 
     def visit_property_stmt(self, stmt: m.PropertyStmt) -> None: ...
 
@@ -127,27 +124,40 @@ class MidasResolver(m.Stmt.Visitor[None], m.Expr.Visitor[Type]):
 
     def visit_predicate_stmt(self, stmt: m.PredicateStmt) -> None: ...
 
-    def visit_simple_type_expr(self, expr: m.SimpleTypeExpr) -> Type:
+    def visit_logical_expr(self, expr: m.LogicalExpr) -> None: ...
-        return self.get_type(expr.name.lexeme)
 
-    def visit_logical_expr(self, expr: m.LogicalExpr) -> Type: ...
+    def visit_binary_expr(self, expr: m.BinaryExpr) -> None: ...
 
-    def visit_binary_expr(self, expr: m.BinaryExpr) -> Type: ...
+    def visit_unary_expr(self, expr: m.UnaryExpr) -> None: ...
 
-    def visit_unary_expr(self, expr: m.UnaryExpr) -> Type: ...
+    def visit_get_expr(self, expr: m.GetExpr) -> None: ...
 
-    def visit_get_expr(self, expr: m.GetExpr) -> Type: ...
+    def visit_variable_expr(self, expr: m.VariableExpr) -> None: ...
 
-    def visit_variable_expr(self, expr: m.VariableExpr) -> Type: ...
+    def visit_grouping_expr(self, expr: m.GroupingExpr) -> None:
-
-    def visit_grouping_expr(self, expr: m.GroupingExpr) -> Type:
         return expr.expr.accept(self)
 
-    def visit_literal_expr(self, expr: m.LiteralExpr) -> Type: ...
+    def visit_literal_expr(self, expr: m.LiteralExpr) -> None: ...
 
-    def visit_wildcard_expr(self, expr: m.WildcardExpr) -> Type: ...
+    def visit_wildcard_expr(self, expr: m.WildcardExpr) -> None: ...
 
-    def visit_template_expr(self, expr: m.TemplateExpr) -> Type: ...
+    def visit_named_type(self, type: m.NamedType) -> Type:
+        return self.get_type(type.name.lexeme)
 
-    def visit_type_expr(self, expr: m.TypeExpr) -> Type:
+    def visit_generic_type(self, type: m.GenericType) -> Type:
-        return self.get_type(expr.name.lexeme)
+        type_: Type = type.type.accept(self)
+        params: list[Type] = [param.accept(self) for param in type.params]
+        # TODO
+        return UnknownType()
+
+    def visit_constraint_type(self, type: m.ConstraintType) -> Type:
+        type_: Type = type.type.accept(self)
+        type.constraint.accept(self)
+        # TODO
+        return UnknownType()
+
+    def visit_complex_type(self, type: m.ComplexType) -> Type:
+        for prop in type.properties:
+            prop.accept(self)
+        # TODO
+        return UnknownType()

syntax/midas.ebnf

@@ -19,16 +19,24 @@ Comparison ::= Unary (ComparisonOp Unary)*
 Equality ::= Comparison (EqualityOp Comparison)*
 Constraint ::= Equality ("&" Equality)*
 
-SimpleType ::= Identifier "?"?
+TemplateParam ::= Identifier ("<:" Type)?
-Template ::= "[" Type "]"
+Template ::= "[" (TemplateParam ("," TemplateParam)*)? "]"
-Type ::= Identifier Template? "?"?
+
+
+TypeProperty ::= Identifier ":" Type
+ComplexType ::= "{" TypeProperty* "}"
+NamedType ::= Identifier
+TypeParams ::= "[" (Type ("," Type)*)? "]"
+GenericType ::= NamedType TypeParams?
+GroupedType ::= "(" Type ")"
+BaseType ::= GroupedType | ComplexType | GenericType
+ConstraintType ::= BaseType ("where" Constraint)?
+Type ::= ConstraintType
 
-TypeProperty ::= Identifier ":" Type ("where" Constraints)?
-ComplexTypeBody ::= "{" TypeProperty* "}"
 OpDefinition ::= "op" Identifier "(" Type ")" "->" Type
 ExtendBody ::= "{" OpDefinition* "}"
 
-TypeStatement ::= "type" Identifier Template? ("(" Type ")" ("where" Constraint)? | ComplexTypeBody)
+TypeStatement ::= "type" Identifier Template? "=" Type
 ExtendStatement ::= "extend" Type ExtendBody
 PredicateStatement ::= "predicate" Identifier "(" Identifier ":" Type ")" "=" Constraint
 

syntax/midas.typ

@@ -43,28 +43,52 @@ svg.railroad .terminal rect {
 {[`constraint` 'equality'*"&"]}
 ```
 
-#let simple-type = ```
+#let template-param = ```
-{[`simple-type` 'identifier' <!, "?">]}
+{[`template-param` 'identifier' <!, ["<:" 'type']>]}
 ```
 
 #let template = ```
-{[`template` "[" 'type' "]"]}
+{[`template` "[" <!, 'template-param'*","> "]"]}
-```
-
-#let type = ```
-{[`type` 'identifier' <!, 'template'> <!, "?">]}
 ```
 
 #let type-property = ```
-{[`type-property` 'identifier' ":" 'type' <!, ["where" 'constraint']>]}
+{[`type-property` 'identifier' ":" 'type']}
 ```
 
-#let type-body = ```
+#let complex-type = ```
-{[`type-body` "{" <!, 'type-property'*!> "}"]}
+{[`complex-type` "{" <!, 'type-property'*!> "}"]}
+```
+
+#let named-type = ```
+{[`named-type` 'identifier']}
+```
+
+#let type-params = ```
+{[`type-params` "[" <!, 'type'*","> "]"]}
+```
+
+#let generic-type = ```
+{[`generic-type` 'named-type' <!, 'type-params'>]}
+```
+
+#let grouped-type = ```
+{[`grouped-type` "(" 'type' ")"]}
+```
+
+#let base-type = ```
+{[`base-type` <'grouped-type', 'complex-type', 'generic-type'>]}
+```
+
+#let constraint-type = ```
+{[`constraint-type` 'base-type' <!, ["where" 'constraint']>]}
+```
+
+#let type = ```
+{[`type` 'constraint-type']}
 ```
 
 #let type-statement = ```
-{[`type-statement` "type" 'identifier' <!, 'template'> <[["(" 'type' ")"] <!, ["where" 'constraint']>], 'type-body'>]}
+{[`type-statement` "type" 'identifier' <!, 'template'> "=" 'type']}
 ```
 
 #let op-definition = ```
@@ -92,11 +116,17 @@ svg.railroad .terminal rect {
   comparison: comparison,
   equality: equality,
   constraint: constraint,
-  simple-type: simple-type,
+  template-param: template-param,
   template: template,
-  type: type,
   type-property: type-property,
-  type-body: type-body,
+  complex-type: complex-type,
+  named-type: named-type,
+  type-params: type-params,
+  generic-type: generic-type,
+  grouped-type: grouped-type,
+  base-type: base-type,
+  constraint-type: constraint-type,
+  type: type,
   type-statement: type-statement,
   op-definition: op-definition,
   extend-statement: extend-statement,
@@ -107,10 +137,16 @@ svg.railroad .terminal rect {
 #let inline = (
   "grouping",
   "value",
+  "template-param",
   "template",
-  "simple-type",
   "type-property",
-  "type-body",
+  "complex-type",
+  "type-params",
+  "named-type",
+  "grouped-type",
+  "generic-type",
+  "base-type",
+  "constraint-type",
   "op-definition",
   "type-statement",
   "extend-statement",

tests/cases/checker/04_custom_types.midas

@@ -1,6 +1,6 @@
-type Meter(float)
+type Meter = float
-type Second(float)
+type Second = float
-type MeterPerSecond(float)
+type MeterPerSecond = float
 
 extend Meter {
     op __add__(Meter) -> Meter

tests/cases/checker/04_custom_types.py

@@ -1,8 +1,6 @@
 # type: ignore
 # ruff: disable [F821]
 
-midas.using("04_custom_types.midas")
-
 distance: Meter = cast(Meter, 123.45)
 time: Second = cast(Second, 6.7)
 speed = distance / time

tests/cases/midas-parser/01_simple_types.midas

@@ -1,15 +1,15 @@
 // Simple custom type derived from float
-type Custom(float)
+type Custom = float
 
 // Simple custom types with constraints
-type Latitude(float) where (-90 <= _ <= 90)
+type Latitude = float where (-90 <= _ <= 90)
-type Longitude(float) where (-180 <= _ <= 180)
+type Longitude = float where (-180 <= _ <= 180)
 
 // Generic custom type (a Difference of T is derived from T, e.g. a difference of floats is a float
-type Difference[T](T)
+type Difference[T] = T
 
 // Complex custom type, containing two values accessible through properties
-type GeoLocation {
+type GeoLocation = {
     lat: Latitude
     lon: Longitude
 }
@@ -24,7 +24,7 @@ extend GeoLocation {
 
 // For complex generics, you need to specify how the genericity the properties
 // are handled
-type Difference[GeoLocation] {
+type Difference[GeoLocation] = {
     lat: Difference[Latitude]
     lon: Difference[Longitude]
 }
@@ -44,11 +44,11 @@ predicate StrictlyPositive(v: float) = v > 0
 predicate Equatorial(loc: GeoLocation) = (-10 <= loc.lat <= 10)
 predicate Arctic(loc: GeoLocation) = (loc.lat >= 66)
 
-type Person {
+type Person = {
     name: str
 
     // Property with an inline constraint
-    age: int? where (0 <= _ < 150)
+    age: Optional[int where (0 <= _ < 150)]
 
     // Property referencing a predicate
     height: float where StrictlyPositive

tests/cases/python-parser/02_custom_types.py

@@ -2,10 +2,6 @@
 # ruff: disable[F821]
 from __future__ import annotations
 
-import midas
-
-midas.using("02_custom_types.midas")
-
 df: Frame[
     location: GeoLocation
 ]

tests/cases/python-parser/02_custom_types.py.ref.json

@@ -1,26 +1,5 @@
 {
   "stmts": [
-    {
-      "_type": "ExpressionStmt",
-      "expr": {
-        "_type": "CallExpr",
-        "callee": {
-          "_type": "GetExpr",
-          "object": {
-            "_type": "VariableExpr",
-            "name": "midas"
-          },
-          "name": "using"
-        },
-        "arguments": [
-          {
-            "_type": "LiteralExpr",
-            "value": "02_custom_types.midas"
-          }
-        ],
-        "keywords": {}
-      }
-    },
     {
       "_type": "TypeAssign",
       "name": "df",

tests/checker.py

@@ -33,6 +33,10 @@ class CheckerTester(Tester):
         if not path.is_file():
             raise TypeError(f"Test '{path}' is not a file")
 
+        types_paths: list[Path] = []
+        types_path: Path = path.with_suffix(".midas")
+        if types_path.exists():
+            types_paths.append(types_path)
         source: str = path.read_text()
         tree: ast.Module = ast.parse(source, filename=path)
         parser = PythonParser()
@@ -40,7 +44,11 @@ class CheckerTester(Tester):
         resolver = Resolver()
         resolver.resolve(*stmts)
         result: CaseResult = CaseResult()
-        checker = Checker(resolver.locals, file_path=path)
+        checker = Checker(
+            resolver.locals,
+            source_path=path,
+            types_paths=types_paths,
+        )
         diagnostics: list[Diagnostic] = checker.check(stmts)
         for diagnostic in diagnostics:
             result.diagnostics.append(

tests/serializer/midas.py

@@ -2,56 +2,60 @@ from typing import Optional, Sequence
 
 from midas.ast.midas import (
     BinaryExpr,
-    ComplexTypeStmt,
+    ComplexType,
+    ConstraintType,
     Expr,
     ExtendStmt,
+    GenericType,
     GetExpr,
     GroupingExpr,
     LiteralExpr,
     LogicalExpr,
+    NamedType,
     OpStmt,
     PredicateStmt,
     PropertyStmt,
-    SimpleTypeExpr,
-    SimpleTypeStmt,
     Stmt,
-    TemplateExpr,
+    Type,
-    TypeExpr,
+    TypeStmt,
     UnaryExpr,
     VariableExpr,
     WildcardExpr,
 )
 
 
-class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
+class MidasAstJsonSerializer(
+    Stmt.Visitor[dict], Expr.Visitor[dict], Type.Visitor[dict]
+):
     """An AST serializer which produces a JSON-compatible structure"""
 
     def serialize(self, stmts: list[Stmt]) -> list[dict]:
         return [stmt.accept(self) for stmt in stmts]
 
-    def _serialize_optional(self, element: Optional[Stmt | Expr]) -> Optional[dict]:
+    def _serialize_optional(
+        self, element: Optional[Stmt | Expr | Type]
+    ) -> Optional[dict]:
         if element is None:
             return None
         return element.accept(self)
 
-    def _serialize_list(self, elements: Sequence[Stmt | Expr]) -> list[dict]:
+    def _serialize_list(self, elements: Sequence[Stmt | Expr | Type]) -> list[dict]:
         return [element.accept(self) for element in elements]
 
-    def visit_simple_type_stmt(self, stmt: SimpleTypeStmt) -> dict:
+    def visit_type_stmt(self, stmt: TypeStmt) -> dict:
         return {
-            "_type": "SimpleTypeStmt",
+            "_type": "TypeStmt",
             "name": stmt.name.lexeme,
-            "template": self._serialize_optional(stmt.template),
+            "params": [
-            "base": stmt.base.accept(self),
+                self._serialize_type_stmt_template_param(param) for param in stmt.params
-            "constraint": self._serialize_optional(stmt.constraint),
+            ],
+            "type": stmt.type.accept(self),
         }
 
-    def visit_complex_type_stmt(self, stmt: ComplexTypeStmt) -> dict:
+    def _serialize_type_stmt_template_param(self, param: TypeStmt.Param) -> dict:
         return {
-            "_type": "ComplexTypeStmt",
+            "name": param.name.lexeme,
-            "name": stmt.name.lexeme,
+            "bound": self._serialize_optional(param.bound),
-            "template": self._serialize_optional(stmt.template),
-            "properties": self._serialize_list(stmt.properties),
         }
 
     def visit_property_stmt(self, stmt: PropertyStmt) -> dict:
@@ -59,7 +63,6 @@ class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
             "_type": "PropertyStmt",
             "name": stmt.name.lexeme,
             "type": stmt.type.accept(self),
-            "constraint": self._serialize_optional(stmt.constraint),
         }
 
     def visit_extend_stmt(self, stmt: ExtendStmt) -> dict:
@@ -86,13 +89,6 @@ class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
             "condition": stmt.condition.accept(self),
         }
 
-    def visit_simple_type_expr(self, expr: SimpleTypeExpr) -> dict:
-        return {
-            "_type": "SimpleTypeExpr",
-            "name": expr.name.lexeme,
-            "optional": expr.optional,
-        }
-
     def visit_logical_expr(self, expr: LogicalExpr) -> dict:
         return {
             "_type": "LogicalExpr",
@@ -144,16 +140,28 @@ class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
     def visit_wildcard_expr(self, expr: WildcardExpr) -> dict:
         return {"_type": "WildcardExpr"}
 
-    def visit_template_expr(self, expr: TemplateExpr) -> dict:
+    def visit_named_type(self, type: NamedType) -> dict:
         return {
-            "_type": "TemplateExpr",
+            "_type": "NamedType",
-            "type": expr.type.accept(self),
+            "name": type.name.lexeme,
         }
 
-    def visit_type_expr(self, expr: TypeExpr) -> dict:
+    def visit_generic_type(self, type: GenericType) -> dict:
         return {
-            "_type": "TypeExpr",
+            "_type": "GenericType",
-            "name": expr.name.lexeme,
+            "type": type.type.accept(self),
-            "template": self._serialize_optional(expr.template),
+            "params": self._serialize_list(type.params),
-            "optional": expr.optional,
+        }
+
+    def visit_constraint_type(self, type: ConstraintType) -> dict:
+        return {
+            "_type": "ConstraintType",
+            "type": type.type.accept(self),
+            "constraint": type.constraint.accept(self),
+        }
+
+    def visit_complex_type(self, type: ComplexType) -> dict:
+        return {
+            "_type": "ComplexType",
+            "properties": self._serialize_list(type.properties),
         }

tests/serializer/python.py

@@ -22,6 +22,7 @@ from midas.ast.python import (
     ReturnStmt,
     SetExpr,
     Stmt,
+    TernaryExpr,
     TypeAssign,
     UnaryExpr,
     VariableExpr,
@@ -245,3 +246,11 @@ class PythonAstJsonSerializer(
             "type": expr.type.accept(self),
             "expr": expr.expr.accept(self),
         }
+
+    def visit_ternary_expr(self, expr: TernaryExpr) -> dict:
+        return {
+            "_type": "TernaryExpr",
+            "test": expr.test.accept(self),
+            "if_true": expr.if_true.accept(self),
+            "if_false": expr.if_false.accept(self),
+        }