Merge pull request 'Avoid raising exceptions, report diagnostics instead' (#42) from fix/remove-raises into main

Reviewed-on: #42

LICENSE

@@ -0,0 +1,202 @@
+
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+   END OF TERMS AND CONDITIONS
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+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
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+   Copyright 2026 Louis Heredero
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README.md

@@ -1,5 +1,11 @@
 <h1>Midas</h1>
 
+<p align="center">
+<img src="assets/icon.svg" width="64">
+</p>
+
+<img src="https://git.kb28.ch/HEL/midas/actions/workflows/tests.yaml/badge.svg">
+
 *Midas* is a type system to _Maintain Integrity of Data with Annotated Structures_. In Greek mythology, [Midas](https://en.wikipedia.org/wiki/Midas) was a Phrygian king who was blessed with the gift of turning everything he touched into gold.
 
 *Midas* aims at providing Python developers with a simple annotation system to enable compile-time integrity and data type checks, as well as generating runtime assertions.
@@ -22,6 +28,8 @@ This framework is being developed as part of a Bachelor's Thesis by Louis Herede
   - [Showing Type Judgements](#showing-type-judgements)
   - [Validating Definitions](#validating-definitions)
 - [Tests](#tests)
+- [Contributing](#contributing)
+- [License](#license)
 </details>
 
 
@@ -161,3 +169,16 @@ Not specifying any subcommand is equivalent to running `run -a`
 - Run specific tests: `run tests/cases/test1.py tests/cases/test2.py ...`
 - Update all tests: `update -a`
 - Update specific tests: `update tests/cases/test1.py tests/cases/test2.py ...`
+
+## Contributing
+
+Feel free to [open an issue](https://git.kb28.ch/HEL/midas/issues) to report a bug or if you experience any issues with Midas.
+
+Contributions are also welcome so feel free to [open a pull request](https://git.kb28.ch/HEL/midas/pulls).
+
+> [!NOTE]
+> As this is part of my bachelor project, I will not accept any contributions before my defense
+
+## License
+
+Midas is distributed under the terms of the Apache-2.0 license. See [LICENSE](LICENSE) for details.

docs/architecture.typ

@@ -1,150 +0,0 @@
-#import "@preview/cetz:0.5.2": canvas, draw
-
-#let diagram-only = false
-
-#set document(
-  title: [Midas Architecture],
-  //author: "Louis Heredero",
-)
-
-#set text(
-  font: "Source Sans 3",
-)
-
-#let diagram = canvas({
-  let framed = draw.content.with(
-    padding: (x: .8em, y: 1em),
-    frame: "rect",
-    stroke: black,
-  )
-  let arrow = draw.line.with(mark: (end: ">", fill: black))
-  framed(
-    (0, 0),
-    name: "python-parser",
-  )[Python parser]
-
-  draw.content(
-    (rel: (0, 1), to: "python-parser.north"),
-    padding: 5pt,
-    anchor: "south",
-    name: "source-py",
-  )[_`source.py`_]
-  arrow("source-py", "python-parser")
-
-  framed(
-    (rel: (3, 0), to: "python-parser.east"),
-    anchor: "west",
-    name: "custom-parser",
-    align(center)[Custom python\ parser],
-  )
-
-  arrow("python-parser", "custom-parser", name: "arrow-python-ast")
-  draw.content(
-    "arrow-python-ast",
-    anchor: "south",
-    padding: 5pt,
-  )[`ast.Module`]
-
-  framed(
-    (rel: (-3, -2), to: "custom-parser.south"),
-    anchor: "east",
-    name: "python-resolver",
-  )[Python Resolver]
-  arrow(
-    "custom-parser",
-    ((), "|-", "python-resolver.east"),
-    "python-resolver",
-    name: "arrow-python-custom-ast",
-  )
-  draw.content(
-    (rel: (1.5, 0), to: "arrow-python-custom-ast.end"),
-    padding: 5pt,
-    anchor: "south",
-  )[P-AST#footnote[#strong[P]ython *AST*]<fn-past>]
-  draw.content(
-    "python-resolver.west",
-    padding: 5pt,
-    anchor: "south-east",
-  )[Resolved P-AST@fn-past]
-
-  draw.circle(
-    (rel: (1, -2), to: "custom-parser.south-east"),
-    radius: .4,
-    name: "midas-loader",
-  )
-  arrow(
-    "custom-parser",
-    "midas-loader",
-    name: "arrow-load-midas",
-    mark: (end: (symbol: ">", fill: black), start: "o"),
-  )
-  draw.content(
-    "arrow-load-midas",
-    anchor: "west",
-    padding: 5pt,
-  )[```python midas.using("types.midas")```]
-
-  framed(
-    (rel: (0, -2), to: "midas-loader.south"),
-    name: "midas-parser",
-  )[Midas lexer/parser]
-  arrow("midas-loader", "midas-parser", name: "arrow-midas-source")
-  draw.content(
-    "arrow-midas-source",
-    anchor: "west",
-    padding: 5pt,
-  )[_`types.midas`_]
-
-
-  framed(
-    (rel: (-2, 0), to: "midas-parser.west"),
-    anchor: "east",
-    name: "midas-resolver",
-  )[Midas Resolver]
-  arrow("midas-parser", "midas-resolver", name: "arrow-midas-ast")
-  draw.content(
-    "arrow-midas-ast",
-    anchor: "south",
-    padding: 5pt,
-  )[M-AST#footnote[#strong[M]idas *AST*]<fn-mast>]
-
-  framed(
-    (rel: (-3, 0), to: "midas-resolver.west"),
-    anchor: "east",
-    name: "checker",
-  )[Checker]
-  arrow("midas-resolver", "checker", name: "arrow-type-ctx")
-  arrow(
-    "python-resolver",
-    ((), "-|", "checker.north"),
-    "checker",
-  )
-  draw.content(
-    "arrow-type-ctx",
-    anchor: "south",
-    padding: 5pt,
-  )[Types context]
-})
-
-#show: doc => if diagram-only {
-  set page(width: auto, height: auto, margin: .5cm)
-  diagram
-} else { doc }
-
-#align(center, title())
-
-#v(1cm)
-
-#figure(
-  diagram,
-  caption: [Midas type-checker architecture],
-)
-
-== Components
-
-- *Python parser*: builtin Python AST parser, extracts abstract syntax from the raw Python source (```python ast.parse(...)```)
-- *Custom python parser*: converts the raw Python AST into custom, more suitable constructs, especially for type annotations
-- *Python resolver*: resolves bindings and references, tracks binding scopes
-- *Midas lexer/parser*: parses a Midas type definition file and extracts its AST
-- *Midas resolver*: walks the AST and fills the environment with the defined types and operations
-- *Checker*: evaluates expressions and checks type coherence

examples/00_syntax_prototype/01_simple_types.py

@@ -1,16 +0,0 @@
-# type: ignore
-# ruff: disable[F821]
-from __future__ import annotations
-
-# A simple data-frame with different column of various simple types
-# Columns can be named and/or typed
-df: Frame[
-    verified: bool,
-    birth_year: int,
-    height: float + ( _ > 0 ) + ( _ < 250 ),
-    name: str,
-    date: datetime,
-    float,  # unnamed
-    unknown: _,  # untyped
-    _  # unnamed and untyped
-]

examples/00_syntax_prototype/02_custom_types.midas

@@ -1,24 +0,0 @@
-// Simple custom type derived from floats
-type Latitude<float>
-type Longitude<float>
-
-// Complex custom type, containing two values accessible through properties
-type GeoLocation<Latitude, Longitude> {
-    lat: Latitude
-    lon: Longitude
-}
-
-type LatitudeDiff<float>
-type LongitudeDiff<float>
-
-// Simple operation defined on our custom types
-op <Latitude> - <Latitude> = <LatitudeDiff>
-op <Longitude> - <Longitude> = <LongitudeDiff>
-
-// Simple custom type with a constraint
-type Age<int + (0 <= _) + (_ < 150)>
-
-// Predefined custom constraints that can be referenced in other definitions
-constraint Positive = _ >= 0
-constraint StrictlyPositive = _ > 0
-//constraint Even = _ % 2 == 0

examples/00_syntax_prototype/02_custom_types.py

@@ -1,30 +0,0 @@
-# type: ignore
-# ruff: disable[F821]
-from __future__ import annotations
-
-# A data-frame using a custom type
-df: Frame[
-    location: GeoLocation
-]
-
-# Properties of a type can be used on a column of that type
-lat: Column[GeoLocation] = df["location"].lat
-lon: Column[GeoLocation] = df["location"].lon
-
-# Unregistered operations between types are not permitted
-lat + lon  # Invalid operation
-
-# Registered operations are permitted
-lat1: Latitude = lat[0]
-lat2: Latitude = lat[1]
-lat_diff: Difference[Latitude] = lat2 - lat1  # Valid operation
-
-# In addition to the type, a column can have one or more constraints, either defined inline or in a separate file
-df2: Frame[
-    age: int + (_ >= 0),
-    height: float + (_ >= 0),
-]
-df2_bis: Frame[
-    age: int + Positive,
-    height: float + Positive,
-]

examples/00_syntax_prototype/03_custom_types_v2.midas

@@ -1,73 +0,0 @@
-// Simple custom type derived from float
-type Custom(float)
-
-// Simple custom types with constraints
-type Latitude(float) where (-90 <= _ <= 90)
-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)
-
-// Complex custom type, containing two values accessible through properties
-type GeoLocation {
-    lat: Latitude
-    lon: Longitude
-}
-
-// Define operations on our custom type
-extend GeoLocation {
-    // This type is compatible with the `-` operation with another GeoLocation
-    // i.e. you can subtract a GeoLocation from another GeoLocation, resulting
-    // in a Difference of GeoLocations
-    op __sub__(GeoLocation) -> Difference[GeoLocation]
-}
-
-// For complex generics, you need to specify how the genericity the properties
-// are handled
-type Difference[GeoLocation] {
-    lat: Difference[Latitude]
-    lon: Difference[Longitude]
-}
-
-// Simple operation defined on our custom types
-extend Latitude {
-    op __sub__(Latitude) -> Difference[Latitude]
-}
-
-extend Longitude {
-    op __sub__(Longitude) -> Difference[Longitude]
-}
-
-// Predefined custom predicates that can be referenced in other definitions
-predicate Positive(v: float) = v >= 0
-predicate StrictlyPositive(v: float) = v > 0
-predicate Equatorial(loc: GeoLocation) = (-10 <= loc.lat <= 10)
-predicate Arctic(loc: GeoLocation) = (loc.lat >= 66)
-
-type Person {
-    name: str
-
-    // Property with an inline constraint
-    age: int? where (0 <= _ < 150)
-
-    // Property referencing a predicate
-    height: float where StrictlyPositive
-
-    home: GeoLocation
-}
-
-// Custom complex type derived from another complex type, with a constraint
-// on a property
-// Multiple proposed syntaxes, not yet defined
-
-// Explicit, but new keyword
-type EquatorialPerson refines Person where Equatorial(_.home)
-
-// Explicit with existing keyword, might be confusing if expectations regarding 'is'
-type EquatorialPerson is Person where Equatorial(_.home)
-
-// Consistent and Python-friendly but can be confused with structural extension
-type EquatorialPerson(Person) where Equatorial(_.home)
-
-// Allow new properties, probably not useful
-type EquatorialPerson extends Person where Equatorial(_.home)

examples/00_syntax_prototype/04_functions.py

@@ -1,15 +0,0 @@
-# type: ignore
-# ruff: disable[F821]
-from __future__ import annotations
-
-
-def func(
-    col1: Column[float + (0 <= _ <= 1)],
-    col2: Column[float + (0 <= _ <= 1)],
-) -> Column[float + (0 <= _ <= 2)]:
-    result: Column[float + (0 <= _ <= 2)] = col1 + col2
-    return result
-
-
-def func2(a: int, /, b: float, *, c: str):
-    pass

examples/00_syntax_prototype/05_custom_types_v3.midas

@@ -1,33 +0,0 @@
-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/01_simple_operations.py

@@ -6,7 +6,7 @@ c = a + b  # -> int
 c = "invalid"  # -> can't assign str to int variable
 
 d = True
-e = d + d
+e = d + d  # -> addition not defined between booleans
 
 f: float = a
 

examples/01_simple_type_checking/02_simple_types.py

@@ -1,6 +1,7 @@
 # type: ignore
 # ruff: disable [F821]
 
-distance: Meter = cast(Meter, 123.45)
-time: Second = cast(Second, 6.7)
+distance = cast(Meter, 123.45)
+time = cast(Second, 6.7)
 speed = distance / time
+print(speed)

examples/01_simple_type_checking/03_control_flow.py

@@ -1,3 +1,5 @@
+# Return types must have a LUB
+# Valid
 def minimum(x: int, y: int):
     if x < y:
         return x
@@ -5,18 +7,28 @@ def minimum(x: int, y: int):
         return y
 
 
+# Invalid
+def func(a: int):
+    if a < 5:
+        return "Oops"
+    return True
+
+
 a = 15
 b = 72
 c = minimum(a, b)
 
 
+# Recursive but typable thanks to return hint
 def factorial(n: int) -> int:
     if n <= 1:
         return 1
     return n * factorial(n - 1)
 
 
-category = "Category 1" if a < 10 else "Category 2"
+# Branches must be of the same type
+category = "Category 1" if a < 10 else "Category 2"  # Valid
+category = "Category 1" if a < 10 else 3  # Invalid
 
 
 def foo() -> None:

examples/01_simple_type_checking/04_complex_types.midas

@@ -15,7 +15,9 @@ extend Coordinate {
 type Difference[T <: float] = T
 type MeterDifference = Difference[Meter]
 
-type CompDiff[T <: float] = {
+type CompDiff[T <: float] = object
+
+extend CompDiff[T <: float] {
     prop d1: Difference[T]
     prop d2: Difference[T]
 }

examples/01_simple_type_checking/04_complex_types.py

@@ -1,20 +1,20 @@
 # type: ignore
 # ruff: disable [F821]
 
-p1: Coordinate
-p2: Coordinate
+p1 = cast(Coordinate, object())
+p2 = cast(Coordinate, object())
 
 diff_x = p2.x - p1.x
 diff_y = p2.y - p1.y
 
 dist = diff_x + diff_y
 
-p2.x += cast(Meter, 1)
+p2.x += cast(Meter, 1.0)
 p2.y = True  # invalid, wrong type
 p2.z = 3  # invalid, no property 'z' on Coordinate
 p2.x.a = 3  # invalid, no properties on Meter
 
-foo: list[float] = []
+foo = cast(list[float], [])
 
 append = foo.append
 
@@ -23,7 +23,7 @@ foo.append(2)
 append(True)  # invalid, must be float
 append(2)
 
-bar: list[list[Meter]]
+bar = cast(list[list[Meter]], [])
 
 bar.append([p2.x])
 

examples/01_simple_type_checking/06_overloads.py

@@ -1,9 +1,9 @@
 # type: ignore
 # ruff: disable [F821]
 
-foo: Foo
-t1: T1
-t2: T2
+foo = cast(Foo, object())
+t1 = cast(T1, object())
+t2 = cast(T2, object())
 
 a = foo.bar(t1)
 b = foo.bar(t2)
@@ -13,6 +13,6 @@ func = foo.bar
 c = func(t1)
 d = func(t2)
 
-t2b: T2b
+t2b = cast(T2b, object())
 
 e = foo.bar(t2b)

examples/02_demonstration/demo_stubs.pyi

@@ -1,14 +0,0 @@
-from __future__ import annotations
-from typing import Generic, TypeVar
-
-class Currency(float): ...
-
-_T0 = TypeVar("_T0", bound=Currency, covariant=True)
-
-class Price(Currency, Generic[_T0]):
-    def __add__(self, _0: Price[_T0], /) -> Price[_T0]: ...
-
-class EUR(Currency): ...
-class USD(Currency): ...
-class CHF(Currency): ...
-class Discount(float): ...

justfile

@@ -0,0 +1,14 @@
+# Local Variables:
+# mode: makefile
+# End:
+set shell := ["bash", "-uc"]
+
+build-docs:
+  typst c --root . docs/manual.typ
+  typst c --root . docs/function_subtyping.typ
+
+tests:
+  uv run -m tests
+
+check-docstrings:
+  uv run scripts/docstring_checker.py

midas/ast/printer/midas.py

@@ -1,6 +1,9 @@
+from typing import final
+
 import midas.ast.midas as m
 
 
+@final
 class MidasPrinter(
     m.Expr.Visitor[str],
     m.Stmt.Visitor[str],

midas/ast/printer/midas_ast.py

@@ -1,7 +1,10 @@
+from typing import final
+
 import midas.ast.midas as m
 from midas.ast.printer.base import AstPrinter
 
 
+@final
 class MidasAstPrinter(
     AstPrinter,
     m.Expr.Visitor[None],

midas/ast/printer/python_ast.py

@@ -1,9 +1,11 @@
 import ast
+from typing import final
 
 import midas.ast.python as p
 from midas.ast.printer.base import AstPrinter
 
 
+@final
 class PythonAstPrinter(
     AstPrinter,
     p.MidasType.Visitor[None],
@@ -115,6 +117,24 @@ class PythonAstPrinter(
                 stmt.iterator.accept(self)
             self._write_sequence("body", stmt.body, last=True)
 
+    def visit_import_stmt(self, stmt: p.ImportStmt) -> None:
+        self._write_line("ImportStmt")
+        with self._child_level(single=True):
+            self._write_sequence("imports", stmt.imports, print_func=self._print_import)
+
+    def visit_from_import_stmt(self, stmt: p.FromImportStmt) -> None:
+        self._write_line("FromImportStmt")
+        with self._child_level():
+            self._write_line(f'module: "{stmt.module}"')
+            self._write_sequence("imports", stmt.imports, print_func=self._print_import)
+            self._write_line(f"level: {stmt.level}", last=True)
+
+    def _print_import(self, import_: p.ImportAlias) -> None:
+        self._write_line("ImportAlias")
+        with self._child_level():
+            self._write_line(f'name: "{import_.name}"')
+            self._write_line(f'alias: "{import_.alias}"')
+
     def visit_raw_stmt(self, stmt: p.RawStmt) -> None:
         self._write_line("RawStmt")
         with self._child_level(single=True):

midas/checker/evaluator.py

@@ -1,5 +1,5 @@
 from dataclasses import dataclass
-from typing import Any, Callable, Optional
+from typing import Any, Callable, Optional, final
 
 import midas.ast.midas as m
 from midas.ast.location import Location
@@ -18,6 +18,7 @@ class PartialPredicate(Predicate):
     """A dictionary of already applied parameters"""
 
 
+@final
 class Evaluator(m.Expr.Visitor[Any]):
     """Helper class to evaluate an expression
 

midas/checker/frames/column_groupby_methods.py

@@ -86,6 +86,9 @@ class ColumnGroupByMethodRegistry(MethodRegistry[Call]):
 
         # TODO: maybe better to filter arguments and pass some, in case the
         # return type depends on them
+
+        # Don't catch UndefinedMethodException because all aggregation
+        # methods should be defined on columns too
         returns: Type = self.typer.call_method(
             location=call.location,
             call_expr=call.call_expr,

midas/checker/frames/frame_groupby_methods.py

@@ -53,6 +53,8 @@ class FrameGroupByMethodRegistry(MethodRegistry[Call]):
         for column in call.groupby.frame.columns:
             with self.reporter.with_context(f"in column '{column.name}'"):
                 column_groupby: ColumnGroupBy = ColumnGroupBy(column=column.type)
+                # Don't catch UndefinedMethodException because all aggregation
+                # methods should be defined on columns too
                 result_type: Type = self.typer.call_method(
                     location=call.location,
                     call_expr=call.call_expr,

midas/checker/midas.py

@@ -1,6 +1,6 @@
 import logging
 from pathlib import Path
-from typing import Optional
+from typing import Optional, final
 
 import midas.ast.midas as m
 from midas.ast.location import Location
@@ -30,6 +30,7 @@ from midas.lexer.token import Token, TokenType
 from midas.parser.midas import MidasParser
 
 
+@final
 class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type]):
     """A resolver which evaluates Midas type definitions and build a registry"""
 
@@ -110,7 +111,7 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
             return self._local_variables[name]
         return self.types.get_type(name)
 
-    def get_variable(self, name: str) -> Type:
+    def get_variable(self, location: Location, name: str) -> Type:
         """Get the type of a variable
 
         This function will first look into the current predicate's parameters if
@@ -118,11 +119,9 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
         The the variable is looked up in the preamble (i.e. global environment)
 
         Args:
+            location (Location): the location of the variable reference
             name (str): the name of the variable
 
-        Raises:
-            NameError: if the variable cannot be found
-
         Returns:
             Type: the type of the variable
         """
@@ -136,7 +135,8 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
         if global_ is not None:
             return global_
 
-        raise NameError(f"Unknown variable '{name}'")
+        self.reporter.error(location, f"Unknown variable '{name}'")
+        return UnknownType()
 
     def resolve(self, stmts: list[m.Stmt]):
         """Process a sequence of statements
@@ -170,7 +170,10 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
             type = GenericType(name=name, params=params, body=type)
         else:
             type = DerivedType(name=name, type=type)
+        try:
             self.types.define_type(name, type)
+        except ValueError:
+            self.reporter.error(stmt.location, f"Type {name} already defined")
         self._local_variables.clear()
         self._current_name = None
 
@@ -178,7 +181,10 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
         name: str = stmt.name.lexeme
         self._current_name = name
         type: Type = stmt.type.accept(self)
+        try:
             self.types.define_type(name, type)
+        except ValueError:
+            self.reporter.error(stmt.location, f"Type {name} already defined")
         self._current_name = None
 
     def visit_member_stmt(self, stmt: m.MemberStmt) -> None: ...
@@ -201,6 +207,7 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
             )
 
     def visit_predicate_stmt(self, stmt: m.PredicateStmt) -> None:
+        name: str = stmt.name.lexeme
         for spec in stmt.params:
             for param in spec.mixed:
                 assert param.name is not None
@@ -222,14 +229,17 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
                     returns=type,
                 )
         self._predicate_params = {}
+        try:
             self.types.define_predicate(
-            stmt.name.lexeme,
+                name,
                 Predicate(
                     type=type,
                     body=stmt.body,
                     alias=len(params) == 0,
                 ),
             )
+        except ValueError:
+            self.reporter.error(stmt.location, f"Predicate {name} already defined")
 
     def _is_valid_predicate(self, body: Type) -> bool:
         """Check whether the given type is valid as a predicate's body
@@ -293,6 +303,9 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
         return result.result
 
     def visit_unary_expr(self, expr: m.UnaryExpr) -> Type:
+        # First evaluate operand to surface all errors
+        operand: Type = self.type_of(expr.right)
+
         # Special case because there is no __not__ dunder method
         match expr.operator:
             case Token(type=TokenType.BANG):
@@ -306,7 +319,6 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
             )
             return UnknownType()
 
-        operand: Type = self.type_of(expr.right)
         operation: Optional[Type] = self.types.lookup_member(operand, method)
         if operation is None:
             self.reporter.error(
@@ -350,7 +362,7 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
         return member
 
     def visit_variable_expr(self, expr: m.VariableExpr) -> Type:
-        return self.get_variable(expr.name.lexeme)
+        return self.get_variable(expr.location, expr.name.lexeme)
 
     def visit_grouping_expr(self, expr: m.GroupingExpr) -> Type:
         return expr.expr.accept(self)
@@ -365,12 +377,14 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
                 return self.types.get_type("float")
             case str():
                 return self.types.get_type("str")
+            case None:
+                return self.types.get_type("None")
             case _:
                 self.reporter.warning(expr.location, f"Unknown literal {expr}")
                 return UnknownType()
 
     def visit_wildcard_expr(self, expr: m.WildcardExpr) -> Type:
-        return self.get_variable("_")
+        return self.get_variable(expr.location, "_")
 
     def visit_named_type(self, type: m.NamedType) -> Type:
         name: str = type.name.lexeme
@@ -409,7 +423,7 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
         self._predicate_params = {}
         if not self.types.is_subtype(constraint_type, self._bool):
             self.reporter.error(
-                type.location,
+                type.constraint.location,
                 f"Constraint must evaluate to a boolean, got {constraint_type}",
             )
 

midas/checker/python.py

@@ -1,6 +1,6 @@
 import ast
 import logging
-from typing import Any, Optional
+from typing import Any, Optional, final
 
 import midas.ast.python as p
 from midas.ast.location import Location
@@ -48,13 +48,16 @@ TypedExpr = tuple[p.Expr, Type]
 
 
 class ReturnException(Exception):
-    pass
+    def __init__(self, stmt: p.Stmt):
+        super().__init__()
+        self.stmt: p.Stmt = stmt
 
 
 class UndefinedMethodException(Exception):
     pass
 
 
+@final
 class PythonTyper(
     p.Stmt.Visitor[None],
     p.Expr.Visitor[Type],
@@ -115,7 +118,10 @@ class PythonTyper(
         self.judgements = []
         self.evaluated_casts = []
 
+        try:
             self.check(stmts)
+        except ReturnException as e:
+            self.reporter.error(e.stmt.location, "Return statement outside of function")
 
         return TypedAST(
             stmts=stmts,
@@ -575,7 +581,7 @@ class PythonTyper(
     def visit_return_stmt(self, stmt: p.ReturnStmt) -> None:
         type: Type = self.type_of(stmt.value) if stmt.value is not None else UnitType()
         self.env.return_types.append(type)
-        raise ReturnException()
+        raise ReturnException(stmt)
 
     def visit_if_stmt(self, stmt: p.IfStmt) -> None:
         # Not evaluated in sub-environment because assignments in the test leak out of the if
@@ -598,7 +604,7 @@ class PythonTyper(
         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()
+            raise ReturnException(stmt)
 
     def visit_pass(self, stmt: p.Pass) -> None:
         pass
@@ -626,7 +632,7 @@ class PythonTyper(
         self.env = outer_env
 
         if body_returned:
-            raise ReturnException()
+            raise ReturnException(stmt)
 
     def visit_import_stmt(self, stmt: p.ImportStmt) -> None:
         self._visit_imports(stmt.location, stmt.imports)
@@ -771,6 +777,7 @@ class PythonTyper(
         match expr.callee:
             case p.GetExpr(object=obj, name=method):
                 obj_type: Type = self.type_of(obj)
+                try:
                     return self.call_method(
                         location=expr.location,
                         call_expr=expr,
@@ -779,6 +786,12 @@ class PythonTyper(
                         positional=positional,
                         keywords=keywords,
                     )
+                except UndefinedMethodException:
+                    self.reporter.error(
+                        expr.location,
+                        f"Unknown method {method} on type {obj_type}",
+                    )
+                    return UnknownType()
 
         callee: Type = self.type_of(expr.callee)
         result: CallResult = self.dispatcher.get_result(
@@ -1000,7 +1013,11 @@ class PythonTyper(
 
         if len(node.args) != 0:
             args: list[Type] = [self.resolve_type_expr(arg) for arg in node.args]
+            try:
                 return self.types.apply_generic(base, args)
+            except Exception as e:
+                self.reporter.error(node.location, f"Cannot apply generic type: {e}")
+                return UnknownType()
         return base
 
     def visit_frame_column(self, node: p.FrameColumn) -> ColumnType:
@@ -1077,10 +1094,13 @@ class PythonTyper(
                 bound: Optional[Type] = None
                 variance: Variance = Variance.INVARIANT
                 if "bound" in call.keywords:
+                    try:
                         bound_type: p.MidasType = self._parse_type_from_expr(
                             call.keywords["bound"]
                         )
                         bound = self.resolve_type_expr(bound_type)
+                    except NotImplementedError:
+                        bound = UnknownType()
 
                 if is_kw_true("covariant"):
                     variance = Variance.COVARIANT
@@ -1095,7 +1115,13 @@ class PythonTyper(
                     else:
                         variance = Variance.CONTRAVARIANT
                 var: TypeVar = TypeVar(name=name, bound=bound, variance=variance)
+                try:
                     self.types.define_type(name, var)
+                except ValueError:
+                    self.reporter.error(
+                        call.location,
+                        f"A type or type variable with the name {name} is already defined",
+                    )
                 return var
 
             case _:
@@ -1126,6 +1152,14 @@ class PythonTyper(
                 return parser._parse_type(node.body)
             case p.VariableExpr(name=name):
                 return p.BaseType(location=location, base=name, args=())
+            case p.SubscriptExpr(object=p.VariableExpr(name=name), index=arg):
+                args: tuple[p.MidasType, ...] = (
+                    tuple(self._parse_type_from_expr(a) for a in arg.items)
+                    if isinstance(arg, p.TupleExpr)
+                    else (self._parse_type_from_expr(arg),)
+                )
+                return p.BaseType(location=location, base=name, args=args)
+
             case _:
                 raise NotImplementedError
 

midas/checker/resolver.py

@@ -1,3 +1,5 @@
+from typing import final
+
 import midas.ast.python as p
 from midas.ast.location import Location
 from midas.checker.reporter import FileReporter
@@ -6,6 +8,7 @@ from midas.checker.reporter import FileReporter
 class ResolverError(Exception): ...
 
 
+@final
 class Resolver(p.Stmt.Visitor[None], p.Expr.Visitor[None]):
     """A variable assignment and reference resolver
 

midas/checker/types.py

@@ -362,9 +362,6 @@ def substitute_typevars(type: Type, substitutions: dict[str, Type]) -> Type:
         case UnknownType() | UnitType():
             return type
 
-        case TopType() | GenericType():
-            raise NotImplementedError(f"Unsupported type {type}")
-
         # Ensure exhaustiveness
         case _:
             assert_never(type)

midas/cli/highlighter.py

@@ -3,7 +3,7 @@ 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
+from typing import Generic, Optional, Protocol, TextIO, TypeVar, final
 
 import midas.ast.midas as m
 import midas.ast.python as p
@@ -121,6 +121,7 @@ class Highlighter(ABC):
                 self.openings.setdefault((l + 1, 0), []).append(opening)
 
 
+@final
 class PythonHighlighter(
     Highlighter,
     p.MidasType.Visitor[None],
@@ -197,6 +198,10 @@ class PythonHighlighter(
         for body_stmt in stmt.body:
             body_stmt.accept(self)
 
+    def visit_import_stmt(self, stmt: p.ImportStmt) -> None: ...
+
+    def visit_from_import_stmt(self, stmt: p.FromImportStmt) -> None: ...
+
     def visit_binary_expr(self, expr: p.BinaryExpr) -> None: ...
 
     def visit_compare_expr(self, expr: p.CompareExpr) -> None: ...
@@ -255,6 +260,7 @@ class PythonHighlighter(
     def visit_raw_stmt(self, stmt: p.RawStmt) -> None: ...
 
 
+@final
 class MidasHighlighter(
     Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[None]
 ):
@@ -263,6 +269,11 @@ class MidasHighlighter(
     def highlight(self, node: Highlightable[MidasHighlighter]):
         node.accept(self)
 
+    def visit_alias_stmt(self, stmt: m.AliasStmt) -> None:
+        self.wrap(stmt, "alias-stmt")
+        self.wrap(LocatableToken(stmt.name), "type-name")
+        stmt.type.accept(self)
+
     def visit_type_stmt(self, stmt: m.TypeStmt) -> None:
         self.wrap(stmt, "type-stmt")
         self.wrap(LocatableToken(stmt.name), "type-name")
@@ -352,6 +363,7 @@ class MidasHighlighter(
         self.wrap(column, "column")
 
 
+@final
 class DiagnosticsHighlighter(Highlighter):
     EXTRA_CSS_PATH: Optional[Path] = Path(__file__).parent / "hl_diagnostic.css"
 

midas/generator/constraints.py

@@ -1,5 +1,5 @@
 import ast
-from typing import Optional
+from typing import Optional, final
 
 import midas.ast.midas as m
 from midas.checker.registry import TypesRegistry
@@ -39,6 +39,7 @@ COMPARISON_OPERATORS: dict[TokenType, type[ast.cmpop]] = {
 }
 
 
+@final
 class ConstraintGenerator(m.Expr.Visitor[ast.expr]):
     """Class to generate Python code for constraint expressions"""
 

midas/generator/generator.py

@@ -3,7 +3,7 @@ import logging
 import shutil
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Optional, assert_never
+from typing import Optional, assert_never, final
 
 import midas.ast.midas as m
 import midas.ast.python as p
@@ -47,6 +47,7 @@ class Scope:
     """A list of aliases defined in the scope, that can be discard afterwards"""
 
 
+@final
 class Generator(p.Stmt.Visitor[ast.stmt], p.Expr.Visitor[ast.expr]):
     """
     A class to translate the custom Python AST back into raw `ast` nodes

test.py

@@ -1,33 +0,0 @@
-import json
-from pathlib import Path
-
-from midas.ast.printer import MidasAstPrinter
-from midas.lexer.midas import MidasLexer
-from midas.lexer.token import Token
-from midas.parser.midas import MidasParser
-
-
-def test_midas():
-    # Midas type definitions
-    path: Path = Path("examples") / "00_syntax_prototype" / "03_custom_types_v2.midas"
-    definitions: str = path.read_text()
-    midas_lexer: MidasLexer = MidasLexer(definitions, path.name)
-    tokens: list[Token] = midas_lexer.process()
-    # print([f"{t.type.name}('{t.lexeme}')" for t in tokens])
-    with open("tokens.json", "w") as f:
-        json.dump([f"{t.type.name}('{t.lexeme}')" for t in tokens], f, indent=4)
-
-    parser = MidasParser(tokens)
-    parsed = parser.parse()
-    print(parsed)
-    for err in parser.errors:
-        print(err.get_report())
-    printer = MidasAstPrinter()
-    for stmt in parsed:
-        if stmt is None:
-            print("None")
-            continue
-        print(printer.print(stmt))
-
-
-test_midas()

tests/cases/checker/11_function_subtyping.py

@@ -0,0 +1,44 @@
+def a1(param: int) -> float: ...
+def a2(param: float) -> int: ...
+
+
+a = a1
+a = a2
+
+
+def b1(a: int, /) -> float: ...
+def b2(b: float, /) -> int: ...
+
+
+b = b1
+b = b2
+
+
+def c1(a: int) -> None: ...
+def c2(p: float = 0, /, *, a: float = 0) -> None: ...
+
+
+c = c1
+c = c2
+
+# Invalid subtypes
+
+
+def d1(a: int) -> float: ...
+def d2(a: str) -> float: ...
+def d3(a: int) -> str: ...
+
+
+d = d1
+d = d2
+d = d3
+
+
+def e1(*, a: int = 0) -> None: ...
+def e2(*, a: int) -> None: ...
+def e3(*, a: int = 0, b: int) -> None: ...
+
+
+e = e1
+e = e2
+e = e3

tests/cases/checker/11_function_subtyping.py.ref.json

@@ -0,0 +1,881 @@
+{
+  "diagnostics": [
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          1,
+          29
+        ],
+        "end": [
+          1,
+          32
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=1, col_offset=29, end_lineno=1, end_col_offset=32), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          1,
+          22
+        ],
+        "end": [
+          1,
+          27
+        ]
+      },
+      "message": "Return type mismatch, annotated float but returns None"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          2,
+          29
+        ],
+        "end": [
+          2,
+          32
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=2, col_offset=29, end_lineno=2, end_col_offset=32), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          2,
+          24
+        ],
+        "end": [
+          2,
+          27
+        ]
+      },
+      "message": "Return type mismatch, annotated int but returns None"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          9,
+          28
+        ],
+        "end": [
+          9,
+          31
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=9, col_offset=28, end_lineno=9, end_col_offset=31), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          9,
+          21
+        ],
+        "end": [
+          9,
+          26
+        ]
+      },
+      "message": "Return type mismatch, annotated float but returns None"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          10,
+          28
+        ],
+        "end": [
+          10,
+          31
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=10, col_offset=28, end_lineno=10, end_col_offset=31), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          10,
+          23
+        ],
+        "end": [
+          10,
+          26
+        ]
+      },
+      "message": "Return type mismatch, annotated int but returns None"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          17,
+          24
+        ],
+        "end": [
+          17,
+          27
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=17, col_offset=24, end_lineno=17, end_col_offset=27), value=Ellipsis)"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          18,
+          50
+        ],
+        "end": [
+          18,
+          53
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=18, col_offset=50, end_lineno=18, end_col_offset=53), value=Ellipsis)"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          27,
+          25
+        ],
+        "end": [
+          27,
+          28
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=27, col_offset=25, end_lineno=27, end_col_offset=28), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          27,
+          18
+        ],
+        "end": [
+          27,
+          23
+        ]
+      },
+      "message": "Return type mismatch, annotated float but returns None"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          28,
+          25
+        ],
+        "end": [
+          28,
+          28
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=28, col_offset=25, end_lineno=28, end_col_offset=28), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          28,
+          18
+        ],
+        "end": [
+          28,
+          23
+        ]
+      },
+      "message": "Return type mismatch, annotated float but returns None"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          29,
+          23
+        ],
+        "end": [
+          29,
+          26
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=29, col_offset=23, end_lineno=29, end_col_offset=26), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          29,
+          18
+        ],
+        "end": [
+          29,
+          21
+        ]
+      },
+      "message": "Return type mismatch, annotated str but returns None"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          33,
+          0
+        ],
+        "end": [
+          33,
+          6
+        ]
+      },
+      "message": "Cannot assign (a: str) -> float to variable 'd' of type (a: int) -> float"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          34,
+          0
+        ],
+        "end": [
+          34,
+          6
+        ]
+      },
+      "message": "Cannot assign (a: int) -> str to variable 'd' of type (a: int) -> float"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          37,
+          31
+        ],
+        "end": [
+          37,
+          34
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=37, col_offset=31, end_lineno=37, end_col_offset=34), value=Ellipsis)"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          38,
+          27
+        ],
+        "end": [
+          38,
+          30
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=38, col_offset=27, end_lineno=38, end_col_offset=30), value=Ellipsis)"
+    },
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          39,
+          39
+        ],
+        "end": [
+          39,
+          42
+        ]
+      },
+      "message": "Unknown literal LiteralExpr(location=Location(lineno=39, col_offset=39, end_lineno=39, end_col_offset=42), value=Ellipsis)"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          43,
+          0
+        ],
+        "end": [
+          43,
+          6
+        ]
+      },
+      "message": "Cannot assign (*, a: int) -> None to variable 'e' of type (*, a: int?) -> None"
+    },
+    {
+      "type": "Error",
+      "location": {
+        "start": [
+          44,
+          0
+        ],
+        "end": [
+          44,
+          6
+        ]
+      },
+      "message": "Cannot assign (*, a: int?, b: int) -> None to variable 'e' of type (*, a: int?) -> None"
+    }
+  ],
+  "judgments": [
+    {
+      "location": {
+        "from": "L1:29",
+        "to": "L1:32"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L2:29",
+        "to": "L2:32"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L5:4",
+        "to": "L5:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "a1"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [
+            {
+              "pos": 0,
+              "name": "param",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "kw": []
+        },
+        "returns": {
+          "name": "float"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L6:4",
+        "to": "L6:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "a2"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [
+            {
+              "pos": 0,
+              "name": "param",
+              "type": {
+                "name": "float"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "kw": []
+        },
+        "returns": {
+          "name": "int"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L9:28",
+        "to": "L9:31"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L10:28",
+        "to": "L10:31"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L13:4",
+        "to": "L13:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "b1"
+      },
+      "type": {
+        "params": {
+          "pos": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "mixed": [],
+          "kw": []
+        },
+        "returns": {
+          "name": "float"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L14:4",
+        "to": "L14:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "b2"
+      },
+      "type": {
+        "params": {
+          "pos": [
+            {
+              "pos": 0,
+              "name": "b",
+              "type": {
+                "name": "float"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "mixed": [],
+          "kw": []
+        },
+        "returns": {
+          "name": "int"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L17:24",
+        "to": "L17:27"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L18:18",
+        "to": "L18:19"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": 0
+      },
+      "type": {
+        "name": "int"
+      }
+    },
+    {
+      "location": {
+        "from": "L18:38",
+        "to": "L18:39"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": 0
+      },
+      "type": {
+        "name": "int"
+      }
+    },
+    {
+      "location": {
+        "from": "L18:50",
+        "to": "L18:53"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L21:4",
+        "to": "L21:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "c1"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "kw": []
+        },
+        "returns": {}
+      }
+    },
+    {
+      "location": {
+        "from": "L22:4",
+        "to": "L22:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "c2"
+      },
+      "type": {
+        "params": {
+          "pos": [
+            {
+              "pos": 0,
+              "name": "p",
+              "type": {
+                "name": "float"
+              },
+              "required": false,
+              "unsupported": false
+            }
+          ],
+          "mixed": [],
+          "kw": [
+            {
+              "pos": 1,
+              "name": "a",
+              "type": {
+                "name": "float"
+              },
+              "required": false,
+              "unsupported": false
+            }
+          ]
+        },
+        "returns": {}
+      }
+    },
+    {
+      "location": {
+        "from": "L27:25",
+        "to": "L27:28"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L28:25",
+        "to": "L28:28"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L29:23",
+        "to": "L29:26"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L32:4",
+        "to": "L32:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "d1"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "kw": []
+        },
+        "returns": {
+          "name": "float"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L33:4",
+        "to": "L33:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "d2"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "str"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "kw": []
+        },
+        "returns": {
+          "name": "float"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L34:4",
+        "to": "L34:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "d3"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ],
+          "kw": []
+        },
+        "returns": {
+          "name": "str"
+        }
+      }
+    },
+    {
+      "location": {
+        "from": "L37:19",
+        "to": "L37:20"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": 0
+      },
+      "type": {
+        "name": "int"
+      }
+    },
+    {
+      "location": {
+        "from": "L37:31",
+        "to": "L37:34"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L38:27",
+        "to": "L38:30"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L39:19",
+        "to": "L39:20"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": 0
+      },
+      "type": {
+        "name": "int"
+      }
+    },
+    {
+      "location": {
+        "from": "L39:39",
+        "to": "L39:42"
+      },
+      "expr": {
+        "_type": "LiteralExpr",
+        "value": "..."
+      },
+      "type": {}
+    },
+    {
+      "location": {
+        "from": "L42:4",
+        "to": "L42:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "e1"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [],
+          "kw": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": false,
+              "unsupported": false
+            }
+          ]
+        },
+        "returns": {}
+      }
+    },
+    {
+      "location": {
+        "from": "L43:4",
+        "to": "L43:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "e2"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [],
+          "kw": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ]
+        },
+        "returns": {}
+      }
+    },
+    {
+      "location": {
+        "from": "L44:4",
+        "to": "L44:6"
+      },
+      "expr": {
+        "_type": "VariableExpr",
+        "name": "e3"
+      },
+      "type": {
+        "params": {
+          "pos": [],
+          "mixed": [],
+          "kw": [
+            {
+              "pos": 0,
+              "name": "a",
+              "type": {
+                "name": "int"
+              },
+              "required": false,
+              "unsupported": false
+            },
+            {
+              "pos": 1,
+              "name": "b",
+              "type": {
+                "name": "int"
+              },
+              "required": true,
+              "unsupported": false
+            }
+          ]
+        },
+        "returns": {}
+      }
+    }
+  ]
+}

tests/cases/generator/03_simple_syntax.py

@@ -0,0 +1,49 @@
+# type: ignore
+# ruff: disable[F821]
+
+import module1
+import module2 as alias2
+from module3 import submodule3
+from module4 import submodule4 as alias4
+
+a: int
+b: Generic[int]
+c: Generic2[int, float]
+d: Frame[a:int, b:float]
+
+e = 3
+f: int = 4
+g = []
+h = [1, 0.1, " ", None, False, True]
+i = {}
+j = {"a": 1, "b": 2}
+k = {"c": 3, **j}
+l = cast(int, a)
+m = unsafe_cast(int, a)
+
+
+def n(a: int, /, b: float, *, c: str) -> Any:
+    return
+
+
+def o(a: int = 1, /, b: float = 2.0, *, c: str = "") -> Any:
+    return 1
+
+
+for i in h:
+    pass
+
+if e == f:
+    pass
+elif f == g:
+    pass
+else:
+    pass
+
+p = +a + -b - ~c * d / e**f
+q = not (a and b) or c
+r = a & b | c ^ d
+
+s = a.b.c
+t = a[b][c, d][e:f]
+u = a(b)(c=d)

tests/cases/generator/03_simple_syntax.py.ref.txt

@@ -0,0 +1,249 @@
+Module(
+  body=[
+    Import(
+      names=[
+        alias(name='module1')]),
+    Import(
+      names=[
+        alias(name='module2', asname='alias2')]),
+    ImportFrom(
+      module='module3',
+      names=[
+        alias(name='submodule3')],
+      level=0),
+    ImportFrom(
+      module='module4',
+      names=[
+        alias(name='submodule4', asname='alias4')],
+      level=0),
+    Assign(
+      targets=[
+        Name(id='e')],
+      value=Constant(value=3)),
+    Assign(
+      targets=[
+        Name(id='f')],
+      value=Constant(value=4)),
+    Assign(
+      targets=[
+        Name(id='g')],
+      value=List(elts=[])),
+    Assign(
+      targets=[
+        Name(id='h')],
+      value=List(
+        elts=[
+          Constant(value=1),
+          Constant(value=0.1),
+          Constant(value=' '),
+          Constant(value=None),
+          Constant(value=False),
+          Constant(value=True)])),
+    Assign(
+      targets=[
+        Name(id='i')],
+      value=Dict(keys=[], values=[])),
+    Assign(
+      targets=[
+        Name(id='j')],
+      value=Dict(
+        keys=[
+          Constant(value='a'),
+          Constant(value='b')],
+        values=[
+          Constant(value=1),
+          Constant(value=2)])),
+    Assign(
+      targets=[
+        Name(id='k')],
+      value=Dict(
+        keys=[
+          Constant(value='c'),
+          None],
+        values=[
+          Constant(value=3),
+          Name(id='j')])),
+    Assign(
+      targets=[
+        Name(id='__midas_a0__')],
+      value=Name(id='a')),
+    Assert(
+      test=Call(
+        func=Name(id='isinstance'),
+        args=[
+          Name(id='__midas_a0__'),
+          Name(id='int')],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='03_simple_syntax.py:L21:5: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a0__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=' to int')])),
+    Assign(
+      targets=[
+        Name(id='l')],
+      value=Name(id='__midas_a0__')),
+    Delete(
+      targets=[
+        Name(id='__midas_a0__')]),
+    Assign(
+      targets=[
+        Name(id='m')],
+      value=Name(id='a')),
+    FunctionDef(
+      name='n',
+      args=arguments(
+        posonlyargs=[
+          arg(arg='a')],
+        args=[
+          arg(arg='b')],
+        kwonlyargs=[
+          arg(arg='c')],
+        kw_defaults=[
+          None],
+        defaults=[]),
+      body=[
+        Return()],
+      decorator_list=[]),
+    FunctionDef(
+      name='o',
+      args=arguments(
+        posonlyargs=[
+          arg(arg='a')],
+        args=[
+          arg(arg='b')],
+        kwonlyargs=[
+          arg(arg='c')],
+        kw_defaults=[
+          Constant(value='')],
+        defaults=[
+          Constant(value=1),
+          Constant(value=2.0)]),
+      body=[
+        Return(
+          value=Constant(value=1))],
+      decorator_list=[]),
+    For(
+      target=Name(id='i'),
+      iter=Name(id='h'),
+      body=[
+        Pass()],
+      orelse=[]),
+    If(
+      test=Compare(
+        left=Name(id='e'),
+        ops=[
+          Eq()],
+        comparators=[
+          Name(id='f')]),
+      body=[
+        Pass()],
+      orelse=[
+        If(
+          test=Compare(
+            left=Name(id='f'),
+            ops=[
+              Eq()],
+            comparators=[
+              Name(id='g')]),
+          body=[
+            Pass()],
+          orelse=[])]),
+    Assign(
+      targets=[
+        Name(id='p')],
+      value=BinOp(
+        left=BinOp(
+          left=UnaryOp(
+            op=UAdd(),
+            operand=Name(id='a')),
+          op=Add(),
+          right=UnaryOp(
+            op=USub(),
+            operand=Name(id='b'))),
+        op=Sub(),
+        right=BinOp(
+          left=BinOp(
+            left=UnaryOp(
+              op=Invert(),
+              operand=Name(id='c')),
+            op=Mult(),
+            right=Name(id='d')),
+          op=Div(),
+          right=BinOp(
+            left=Name(id='e'),
+            op=Pow(),
+            right=Name(id='f'))))),
+    Assign(
+      targets=[
+        Name(id='q')],
+      value=BoolOp(
+        op=Or(),
+        values=[
+          UnaryOp(
+            op=Not(),
+            operand=BoolOp(
+              op=And(),
+              values=[
+                Name(id='a'),
+                Name(id='b')])),
+          Name(id='c')])),
+    Assign(
+      targets=[
+        Name(id='r')],
+      value=BinOp(
+        left=BinOp(
+          left=Name(id='a'),
+          op=BitAnd(),
+          right=Name(id='b')),
+        op=BitOr(),
+        right=BinOp(
+          left=Name(id='c'),
+          op=BitXor(),
+          right=Name(id='d')))),
+    Assign(
+      targets=[
+        Name(id='s')],
+      value=Attribute(
+        value=Attribute(
+          value=Name(id='a'),
+          attr='b'),
+        attr='c')),
+    Assign(
+      targets=[
+        Name(id='t')],
+      value=Subscript(
+        value=Subscript(
+          value=Subscript(
+            value=Name(id='a'),
+            slice=Name(id='b')),
+          slice=Tuple(
+            elts=[
+              Name(id='c'),
+              Name(id='d')])),
+        slice=Slice(
+          lower=Name(id='e'),
+          upper=Name(id='f')))),
+    Assign(
+      targets=[
+        Name(id='u')],
+      value=Call(
+        func=Call(
+          func=Name(id='a'),
+          args=[
+            Name(id='b')],
+          keywords=[]),
+        args=[],
+        keywords=[
+          keyword(
+            arg='c',
+            value=Name(id='d'))]))],
+  type_ignores=[])

tests/cases/generator/04_frames.midas

@@ -0,0 +1,15 @@
+predicate is_positive(v: float) = v >= 0
+type Positive = float where is_positive(_)
+
+alias T1 = Frame[
+    a: int
+]
+
+alias T2 = Frame[
+    a: int,
+    b: str,
+    c: Positive,
+    d: float where is_positive(_)
+]
+
+alias Positives = Column[Positive]

tests/cases/generator/04_frames.py

@@ -0,0 +1,13 @@
+from typing import Any
+
+from midas import T1, T2, Column, Positive, Positives, cast
+
+o: Any = object()
+
+df1 = cast(T1, o)
+df2 = cast(T2, o)
+
+df1 + df2
+
+col1: Positives = df2["c"]
+col2 = cast(Column[Positive], col1)

tests/cases/generator/04_frames.py.ref.txt

@@ -0,0 +1,731 @@
+Module(
+  body=[
+    FunctionDef(
+      name='__midas_column_same_length__',
+      args=arguments(
+        posonlyargs=[],
+        args=[
+          arg(arg='column1'),
+          arg(arg='column2')],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Return(
+          value=Compare(
+            left=Call(
+              func=Name(id='len'),
+              args=[
+                Attribute(
+                  value=Name(id='column1'),
+                  attr='index')],
+              keywords=[]),
+            ops=[
+              Eq()],
+            comparators=[
+              Call(
+                func=Name(id='len'),
+                args=[
+                  Attribute(
+                    value=Name(id='column2'),
+                    attr='index')],
+                keywords=[])]))],
+      decorator_list=[]),
+    FunctionDef(
+      name='__midas_frame_same_length__',
+      args=arguments(
+        posonlyargs=[],
+        args=[
+          arg(arg='frame1'),
+          arg(arg='frame2')],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Return(
+          value=Compare(
+            left=Call(
+              func=Name(id='len'),
+              args=[
+                Attribute(
+                  value=Name(id='frame1'),
+                  attr='index')],
+              keywords=[]),
+            ops=[
+              Eq()],
+            comparators=[
+              Call(
+                func=Name(id='len'),
+                args=[
+                  Attribute(
+                    value=Name(id='frame2'),
+                    attr='index')],
+                keywords=[])]))],
+      decorator_list=[]),
+    FunctionDef(
+      name='__midas_is_column__',
+      args=arguments(
+        posonlyargs=[
+          arg(arg='obj')],
+        args=[],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Import(
+          names=[
+            alias(name='pandas', asname='pd')]),
+        Return(
+          value=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='obj'),
+              Attribute(
+                value=Name(id='pd'),
+                attr='Series')],
+            keywords=[]))],
+      decorator_list=[],
+      returns=Name(id='bool')),
+    FunctionDef(
+      name='__midas_is_dataframe__',
+      args=arguments(
+        posonlyargs=[
+          arg(arg='obj')],
+        args=[],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Import(
+          names=[
+            alias(name='pandas', asname='pd')]),
+        Return(
+          value=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='obj'),
+              Attribute(
+                value=Name(id='pd'),
+                attr='DataFrame')],
+            keywords=[]))],
+      decorator_list=[],
+      returns=Name(id='bool')),
+    FunctionDef(
+      name='__midas_is_positive__',
+      args=arguments(
+        posonlyargs=[],
+        args=[
+          arg(
+            arg='v',
+            annotation=Constant(value='float'))],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Return(
+          value=Compare(
+            left=Name(id='v'),
+            ops=[
+              GtE()],
+            comparators=[
+              Constant(value=0)]))],
+      decorator_list=[],
+      returns=Constant(value='bool')),
+    FunctionDef(
+      name='__midas_p0__',
+      args=arguments(
+        posonlyargs=[],
+        args=[
+          arg(
+            arg='_',
+            annotation=Constant(value='Any'))],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Return(
+          value=Call(
+            func=Name(id='__midas_is_positive__'),
+            args=[
+              Name(id='_')],
+            keywords=[]))],
+      decorator_list=[],
+      returns=Constant(value='bool')),
+    FunctionDef(
+      name='__midas_p1__',
+      args=arguments(
+        posonlyargs=[],
+        args=[
+          arg(
+            arg='_',
+            annotation=Constant(value='Any'))],
+        kwonlyargs=[],
+        kw_defaults=[],
+        defaults=[]),
+      body=[
+        Return(
+          value=Call(
+            func=Name(id='__midas_is_positive__'),
+            args=[
+              Name(id='_')],
+            keywords=[]))],
+      decorator_list=[],
+      returns=Constant(value='bool')),
+    ImportFrom(
+      module='typing',
+      names=[
+        alias(name='Any')],
+      level=0),
+    ImportFrom(
+      module='midas',
+      names=[
+        alias(name='T1'),
+        alias(name='T2'),
+        alias(name='Column'),
+        alias(name='Positive'),
+        alias(name='Positives'),
+        alias(name='cast')],
+      level=0),
+    Assign(
+      targets=[
+        Name(id='o')],
+      value=Call(
+        func=Name(id='object'),
+        args=[],
+        keywords=[])),
+    Assign(
+      targets=[
+        Name(id='__midas_a0__')],
+      value=Name(id='o')),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_dataframe__'),
+        args=[
+          Name(id='__midas_a0__')],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L7:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a0__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=' to Frame[a: Column[int]]: Not a dataframe')])),
+    Assert(
+      test=Compare(
+        left=Constant(value='a'),
+        ops=[
+          In()],
+        comparators=[
+          Name(id='__midas_a0__')]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L7:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a0__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Frame[a: Column[int]]: Missing column 'a'")])),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_column__'),
+        args=[
+          Subscript(
+            value=Name(id='__midas_a0__'),
+            slice=Constant(value='a'))],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L7:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Subscript(
+                    value=Name(id='__midas_a0__'),
+                    slice=Constant(value='a'))],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Column[int], in column 'a': Not a column")])),
+    For(
+      target=Name(id='value'),
+      iter=Subscript(
+        value=Name(id='__midas_a0__'),
+        slice=Constant(value='a')),
+      body=[
+        Assert(
+          test=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='value'),
+              Name(id='int')],
+            keywords=[]),
+          msg=JoinedStr(
+            values=[
+              Constant(value='04_frames.py:L7:7: CastError: Cannot cast '),
+              FormattedValue(
+                value=Attribute(
+                  value=Call(
+                    func=Name(id='type'),
+                    args=[
+                      Name(id='value')],
+                    keywords=[]),
+                  attr='__name__'),
+                conversion=-1),
+              Constant(value=" to int, in column 'a'")]))],
+      orelse=[]),
+    Assign(
+      targets=[
+        Name(id='df1')],
+      value=Name(id='__midas_a0__')),
+    Delete(
+      targets=[
+        Name(id='__midas_a0__')]),
+    Assign(
+      targets=[
+        Name(id='__midas_a1__')],
+      value=Name(id='o')),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_dataframe__'),
+        args=[
+          Name(id='__midas_a1__')],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a1__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=' to Frame[a: Column[int], b: Column[str], c: Column[Positive], d: Column[float where is_positive(_)]]: Not a dataframe')])),
+    Assert(
+      test=Compare(
+        left=Constant(value='a'),
+        ops=[
+          In()],
+        comparators=[
+          Name(id='__midas_a1__')]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a1__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Frame[a: Column[int], b: Column[str], c: Column[Positive], d: Column[float where is_positive(_)]]: Missing column 'a'")])),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_column__'),
+        args=[
+          Subscript(
+            value=Name(id='__midas_a1__'),
+            slice=Constant(value='a'))],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Subscript(
+                    value=Name(id='__midas_a1__'),
+                    slice=Constant(value='a'))],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Column[int], in column 'a': Not a column")])),
+    For(
+      target=Name(id='value'),
+      iter=Subscript(
+        value=Name(id='__midas_a1__'),
+        slice=Constant(value='a')),
+      body=[
+        Assert(
+          test=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='value'),
+              Name(id='int')],
+            keywords=[]),
+          msg=JoinedStr(
+            values=[
+              Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+              FormattedValue(
+                value=Attribute(
+                  value=Call(
+                    func=Name(id='type'),
+                    args=[
+                      Name(id='value')],
+                    keywords=[]),
+                  attr='__name__'),
+                conversion=-1),
+              Constant(value=" to int, in column 'a'")]))],
+      orelse=[]),
+    Assert(
+      test=Compare(
+        left=Constant(value='b'),
+        ops=[
+          In()],
+        comparators=[
+          Name(id='__midas_a1__')]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a1__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Frame[a: Column[int], b: Column[str], c: Column[Positive], d: Column[float where is_positive(_)]]: Missing column 'b'")])),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_column__'),
+        args=[
+          Subscript(
+            value=Name(id='__midas_a1__'),
+            slice=Constant(value='b'))],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Subscript(
+                    value=Name(id='__midas_a1__'),
+                    slice=Constant(value='b'))],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Column[str], in column 'b': Not a column")])),
+    For(
+      target=Name(id='value'),
+      iter=Subscript(
+        value=Name(id='__midas_a1__'),
+        slice=Constant(value='b')),
+      body=[
+        Assert(
+          test=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='value'),
+              Name(id='str')],
+            keywords=[]),
+          msg=JoinedStr(
+            values=[
+              Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+              FormattedValue(
+                value=Attribute(
+                  value=Call(
+                    func=Name(id='type'),
+                    args=[
+                      Name(id='value')],
+                    keywords=[]),
+                  attr='__name__'),
+                conversion=-1),
+              Constant(value=" to str, in column 'b'")]))],
+      orelse=[]),
+    Assert(
+      test=Compare(
+        left=Constant(value='c'),
+        ops=[
+          In()],
+        comparators=[
+          Name(id='__midas_a1__')]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a1__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Frame[a: Column[int], b: Column[str], c: Column[Positive], d: Column[float where is_positive(_)]]: Missing column 'c'")])),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_column__'),
+        args=[
+          Subscript(
+            value=Name(id='__midas_a1__'),
+            slice=Constant(value='c'))],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Subscript(
+                    value=Name(id='__midas_a1__'),
+                    slice=Constant(value='c'))],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Column[Positive], in column 'c': Not a column")])),
+    For(
+      target=Name(id='value'),
+      iter=Subscript(
+        value=Name(id='__midas_a1__'),
+        slice=Constant(value='c')),
+      body=[
+        Assert(
+          test=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='value'),
+              Name(id='float')],
+            keywords=[]),
+          msg=JoinedStr(
+            values=[
+              Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+              FormattedValue(
+                value=Attribute(
+                  value=Call(
+                    func=Name(id='type'),
+                    args=[
+                      Name(id='value')],
+                    keywords=[]),
+                  attr='__name__'),
+                conversion=-1),
+              Constant(value=" to float, in column 'c'")])),
+        Assert(
+          test=Call(
+            func=Name(id='__midas_p0__'),
+            args=[
+              Name(id='value')],
+            keywords=[]),
+          msg=Constant(value="04_frames.py:L8:7: ConstraintError: Value does not fit constraint 'is_positive(_)', in column 'c'"))],
+      orelse=[]),
+    Assert(
+      test=Compare(
+        left=Constant(value='d'),
+        ops=[
+          In()],
+        comparators=[
+          Name(id='__midas_a1__')]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a1__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Frame[a: Column[int], b: Column[str], c: Column[Positive], d: Column[float where is_positive(_)]]: Missing column 'd'")])),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_column__'),
+        args=[
+          Subscript(
+            value=Name(id='__midas_a1__'),
+            slice=Constant(value='d'))],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Subscript(
+                    value=Name(id='__midas_a1__'),
+                    slice=Constant(value='d'))],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=" to Column[float where is_positive(_)], in column 'd': Not a column")])),
+    For(
+      target=Name(id='value'),
+      iter=Subscript(
+        value=Name(id='__midas_a1__'),
+        slice=Constant(value='d')),
+      body=[
+        Assert(
+          test=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='value'),
+              Name(id='float')],
+            keywords=[]),
+          msg=JoinedStr(
+            values=[
+              Constant(value='04_frames.py:L8:7: CastError: Cannot cast '),
+              FormattedValue(
+                value=Attribute(
+                  value=Call(
+                    func=Name(id='type'),
+                    args=[
+                      Name(id='value')],
+                    keywords=[]),
+                  attr='__name__'),
+                conversion=-1),
+              Constant(value=" to float, in column 'd'")])),
+        Assert(
+          test=Call(
+            func=Name(id='__midas_p1__'),
+            args=[
+              Name(id='value')],
+            keywords=[]),
+          msg=Constant(value="04_frames.py:L8:7: ConstraintError: Value does not fit constraint 'is_positive(_)', in column 'd'"))],
+      orelse=[]),
+    Assign(
+      targets=[
+        Name(id='df2')],
+      value=Name(id='__midas_a1__')),
+    Delete(
+      targets=[
+        Name(id='__midas_a1__')]),
+    Assign(
+      targets=[
+        Name(id='__midas_a2__')],
+      value=Name(id='df1')),
+    Assign(
+      targets=[
+        Name(id='__midas_a3__')],
+      value=Name(id='df2')),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_column_same_length__'),
+        args=[
+          Name(id='__midas_a2__'),
+          Name(id='__midas_a3__')],
+        keywords=[]),
+      msg=Constant(value='04_frames.py:L10:1: AssertionError: Columns must have the same length')),
+    Assign(
+      targets=[
+        Name(id='__midas_a4__')],
+      value=Name(id='__midas_a2__')),
+    Assign(
+      targets=[
+        Name(id='__midas_a5__')],
+      value=Name(id='__midas_a3__')),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_frame_same_length__'),
+        args=[
+          Name(id='__midas_a4__'),
+          Name(id='__midas_a5__')],
+        keywords=[]),
+      msg=Constant(value='04_frames.py:L10:1: AssertionError: DataFrames must have the same length')),
+    Expr(
+      value=BinOp(
+        left=Name(id='__midas_a2__'),
+        op=Add(),
+        right=Name(id='__midas_a3__'))),
+    Delete(
+      targets=[
+        Name(id='__midas_a2__'),
+        Name(id='__midas_a3__'),
+        Name(id='__midas_a4__'),
+        Name(id='__midas_a5__')]),
+    Assign(
+      targets=[
+        Name(id='col1')],
+      value=Subscript(
+        value=Name(id='df2'),
+        slice=Constant(value='c'))),
+    Assign(
+      targets=[
+        Name(id='__midas_a6__')],
+      value=Name(id='col1')),
+    Assert(
+      test=Call(
+        func=Name(id='__midas_is_column__'),
+        args=[
+          Name(id='__midas_a6__')],
+        keywords=[]),
+      msg=JoinedStr(
+        values=[
+          Constant(value='04_frames.py:L13:8: CastError: Cannot cast '),
+          FormattedValue(
+            value=Attribute(
+              value=Call(
+                func=Name(id='type'),
+                args=[
+                  Name(id='__midas_a6__')],
+                keywords=[]),
+              attr='__name__'),
+            conversion=-1),
+          Constant(value=' to Column[Positive]: Not a column')])),
+    For(
+      target=Name(id='value'),
+      iter=Name(id='__midas_a6__'),
+      body=[
+        Assert(
+          test=Call(
+            func=Name(id='isinstance'),
+            args=[
+              Name(id='value'),
+              Name(id='float')],
+            keywords=[]),
+          msg=JoinedStr(
+            values=[
+              Constant(value='04_frames.py:L13:8: CastError: Cannot cast '),
+              FormattedValue(
+                value=Attribute(
+                  value=Call(
+                    func=Name(id='type'),
+                    args=[
+                      Name(id='value')],
+                    keywords=[]),
+                  attr='__name__'),
+                conversion=-1),
+              Constant(value=' to float')])),
+        Assert(
+          test=Call(
+            func=Name(id='__midas_p0__'),
+            args=[
+              Name(id='value')],
+            keywords=[]),
+          msg=Constant(value="04_frames.py:L13:8: ConstraintError: Value does not fit constraint 'is_positive(_)'"))],
+      orelse=[]),
+    Assign(
+      targets=[
+        Name(id='col2')],
+      value=Name(id='__midas_a6__')),
+    Delete(
+      targets=[
+        Name(id='__midas_a6__')])],
+  type_ignores=[])

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

@@ -2,8 +2,8 @@
 type Custom = float
 
 // Simple custom types with constraints
-type Latitude = float where (-90 <= _ <= 90)
-type Longitude = float where (-180 <= _ <= 180)
+type Latitude = float where (-90 <= _ & _ <= 90)
+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
@@ -54,10 +54,10 @@ extend Person {
     prop name: str
 
     // Property with an inline constraint
-    prop age: Optional[int where (0 <= _ < 150)]
+    prop age: int where (0 <= _ & _ < 150)
 
     // Property referencing a predicate
-    prop height: float where StrictlyPositive
+    prop height: float where StrictlyPositive(_)
 
     prop home: GeoLocation
 }

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

@@ -187,8 +187,8 @@
       "column": 38
     },
     {
-      "type": "LESS_EQUAL",
-      "lexeme": "<=",
+      "type": "AND",
+      "lexeme": "&",
       "line": 5,
       "column": 39
     },
@@ -196,25 +196,49 @@
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 5,
+      "column": 40
+    },
+    {
+      "type": "UNDERSCORE",
+      "lexeme": "_",
+      "line": 5,
       "column": 41
     },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 5,
+      "column": 42
+    },
+    {
+      "type": "LESS_EQUAL",
+      "lexeme": "<=",
+      "line": 5,
+      "column": 43
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 5,
+      "column": 45
+    },
     {
       "type": "NUMBER",
       "lexeme": "90",
       "line": 5,
-      "column": 42
+      "column": 46
     },
     {
       "type": "RIGHT_PAREN",
       "lexeme": ")",
       "line": 5,
-      "column": 44
+      "column": 48
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 5,
-      "column": 45
+      "column": 49
     },
     {
       "type": "TYPE",
@@ -325,8 +349,8 @@
       "column": 40
     },
     {
-      "type": "LESS_EQUAL",
-      "lexeme": "<=",
+      "type": "AND",
+      "lexeme": "&",
       "line": 6,
       "column": 41
     },
@@ -334,25 +358,49 @@
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 6,
+      "column": 42
+    },
+    {
+      "type": "UNDERSCORE",
+      "lexeme": "_",
+      "line": 6,
       "column": 43
     },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 6,
+      "column": 44
+    },
+    {
+      "type": "LESS_EQUAL",
+      "lexeme": "<=",
+      "line": 6,
+      "column": 45
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 6,
+      "column": 47
+    },
     {
       "type": "NUMBER",
       "lexeme": "180",
       "line": 6,
-      "column": 44
+      "column": 48
     },
     {
       "type": "RIGHT_PAREN",
       "lexeme": ")",
       "line": 6,
-      "column": 47
+      "column": 51
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 6,
-      "column": 48
+      "column": 52
     },
     {
       "type": "NEWLINE",
@@ -2240,22 +2288,40 @@
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "Optional",
+      "lexeme": "int",
       "line": 57,
       "column": 15
     },
     {
-      "type": "LEFT_BRACKET",
-      "lexeme": "[",
+      "type": "WHITESPACE",
+      "lexeme": " ",
       "line": 57,
-      "column": 23
+      "column": 18
     },
     {
-      "type": "IDENTIFIER",
-      "lexeme": "int",
+      "type": "WHERE",
+      "lexeme": "where",
+      "line": 57,
+      "column": 19
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
       "line": 57,
       "column": 24
     },
+    {
+      "type": "LEFT_PAREN",
+      "lexeme": "(",
+      "line": 57,
+      "column": 25
+    },
+    {
+      "type": "NUMBER",
+      "lexeme": "0",
+      "line": 57,
+      "column": 26
+    },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
@@ -2263,8 +2329,8 @@
       "column": 27
     },
     {
-      "type": "WHERE",
-      "lexeme": "where",
+      "type": "LESS_EQUAL",
+      "lexeme": "<=",
       "line": 57,
       "column": 28
     },
@@ -2272,17 +2338,35 @@
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 57,
+      "column": 30
+    },
+    {
+      "type": "UNDERSCORE",
+      "lexeme": "_",
+      "line": 57,
+      "column": 31
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 32
+    },
+    {
+      "type": "AND",
+      "lexeme": "&",
+      "line": 57,
       "column": 33
     },
     {
-      "type": "LEFT_PAREN",
-      "lexeme": "(",
+      "type": "WHITESPACE",
+      "lexeme": " ",
       "line": 57,
       "column": 34
     },
     {
-      "type": "NUMBER",
-      "lexeme": "0",
+      "type": "UNDERSCORE",
+      "lexeme": "_",
       "line": 57,
       "column": 35
     },
@@ -2293,8 +2377,8 @@
       "column": 36
     },
     {
-      "type": "LESS_EQUAL",
-      "lexeme": "<=",
+      "type": "LESS",
+      "lexeme": "<",
       "line": 57,
       "column": 37
     },
@@ -2302,55 +2386,25 @@
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 57,
-      "column": 39
-    },
-    {
-      "type": "UNDERSCORE",
-      "lexeme": "_",
-      "line": 57,
-      "column": 40
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 57,
-      "column": 41
-    },
-    {
-      "type": "LESS",
-      "lexeme": "<",
-      "line": 57,
-      "column": 42
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 57,
-      "column": 43
+      "column": 38
     },
     {
       "type": "NUMBER",
       "lexeme": "150",
       "line": 57,
-      "column": 44
+      "column": 39
     },
     {
       "type": "RIGHT_PAREN",
       "lexeme": ")",
       "line": 57,
-      "column": 47
-    },
-    {
-      "type": "RIGHT_BRACKET",
-      "lexeme": "]",
-      "line": 57,
-      "column": 48
+      "column": 42
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 57,
-      "column": 49
+      "column": 43
     },
     {
       "type": "NEWLINE",
@@ -2442,11 +2496,29 @@
       "line": 60,
       "column": 30
     },
+    {
+      "type": "LEFT_PAREN",
+      "lexeme": "(",
+      "line": 60,
+      "column": 46
+    },
+    {
+      "type": "UNDERSCORE",
+      "lexeme": "_",
+      "line": 60,
+      "column": 47
+    },
+    {
+      "type": "RIGHT_PAREN",
+      "lexeme": ")",
+      "line": 60,
+      "column": 48
+    },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 60,
-      "column": 46
+      "column": 49
     },
     {
       "type": "NEWLINE",
@@ -2544,7 +2616,7 @@
         "constraint": {
           "_type": "GroupingExpr",
           "expr": {
-            "_type": "BinaryExpr",
+            "_type": "LogicalExpr",
             "left": {
               "_type": "BinaryExpr",
               "left": {
@@ -2560,6 +2632,12 @@
                 "_type": "WildcardExpr"
               }
             },
+            "operator": "&",
+            "right": {
+              "_type": "BinaryExpr",
+              "left": {
+                "_type": "WildcardExpr"
+              },
               "operator": "<=",
               "right": {
                 "_type": "LiteralExpr",
@@ -2568,6 +2646,7 @@
             }
           }
         }
+      }
     },
     {
       "_type": "TypeStmt",
@@ -2582,7 +2661,7 @@
         "constraint": {
           "_type": "GroupingExpr",
           "expr": {
-            "_type": "BinaryExpr",
+            "_type": "LogicalExpr",
             "left": {
               "_type": "BinaryExpr",
               "left": {
@@ -2598,6 +2677,12 @@
                 "_type": "WildcardExpr"
               }
             },
+            "operator": "&",
+            "right": {
+              "_type": "BinaryExpr",
+              "left": {
+                "_type": "WildcardExpr"
+              },
               "operator": "<=",
               "right": {
                 "_type": "LiteralExpr",
@@ -2606,6 +2691,7 @@
             }
           }
         }
+      }
     },
     {
       "_type": "TypeStmt",
@@ -3013,13 +3099,6 @@
           "kind": "PROPERTY",
           "name": "age",
           "type": {
-            "_type": "GenericType",
-            "type": {
-              "_type": "NamedType",
-              "name": "Optional"
-            },
-            "args": [
-              {
             "_type": "ConstraintType",
             "type": {
               "_type": "NamedType",
@@ -3028,7 +3107,7 @@
             "constraint": {
               "_type": "GroupingExpr",
               "expr": {
-                    "_type": "BinaryExpr",
+                "_type": "LogicalExpr",
                 "left": {
                   "_type": "BinaryExpr",
                   "left": {
@@ -3040,6 +3119,12 @@
                     "_type": "WildcardExpr"
                   }
                 },
+                "operator": "&",
+                "right": {
+                  "_type": "BinaryExpr",
+                  "left": {
+                    "_type": "WildcardExpr"
+                  },
                   "operator": "<",
                   "right": {
                     "_type": "LiteralExpr",
@@ -3048,7 +3133,6 @@
                 }
               }
             }
-            ]
           }
         },
         {
@@ -3062,8 +3146,17 @@
               "name": "float"
             },
             "constraint": {
+              "_type": "CallExpr",
+              "callee": {
                 "_type": "VariableExpr",
                 "name": "StrictlyPositive"
+              },
+              "arguments": [
+                {
+                  "_type": "WildcardExpr"
+                }
+              ],
+              "keywords": {}
             }
           }
         },

tests/cases/midas-parser/02_all_syntax.midas

@@ -0,0 +1,35 @@
+// Alias declaration
+alias A = object
+
+// Type declaration
+type B = object
+
+// Generic declaration
+type C[T] = object
+type D[T <: A] = object
+type E[T, U] = object
+
+// Type expressions
+type F[T] = T
+type G = A where predicate(_)
+type H = A where _ > 0 & _.attr < 1.0 & +_ + 4.0 >= "string" & !(-_ - 4.0 <= 0 & _ == none & _ != false)
+type I = fn() -> Any
+type J = fn(a: int, /, b: float, *, c: bool) -> Any
+type K = fn(a: int, /, b: float, *, c: bool?) -> Any
+type L = fn(a: int, /, b: float?, *, c: bool?) -> Any
+type M = fn(a: int?, /, b: float?, *, c: bool?) -> Any
+
+// Extend
+extend N {}
+extend O {
+    prop a: int
+    def b: fn(int, /) -> int
+    def b: fn(float, /) -> float
+}
+
+// Predicate
+predicate P = true
+predicate Q(v: float) = v > 0
+predicate R(a: float, b: float)(v: float) = a < v & v < b
+predicate S = R(0.0, 1.0)
+predicate T = R(a=0.0, b=1.0)

tests/cases/python-parser/04_all_syntax.py

@@ -0,0 +1,49 @@
+# type: ignore
+# ruff: disable[F821]
+
+import module1
+import module2 as alias2
+from module3 import submodule3
+from module4 import submodule4 as alias4
+
+a: int
+b: Generic[int]
+c: Generic2[int, float]
+d: Frame[a:int, b:float]
+
+e = 3
+f: int = 4
+g = []
+h = [1, 0.1, " ", None, False, True]
+i = {}
+j = {"a": 1, "b": 2}
+k = {"c": 3, **j}
+l = cast(int, a)
+m = unsafe_cast(int, a)
+
+
+def n(a: int, /, b: float, *, c: str) -> Any:
+    return
+
+
+def o(a: int = 1, /, b: float = 2.0, *, c: str = "") -> Any:
+    return 1
+
+
+for i in h:
+    pass
+
+if e == f:
+    pass
+elif f == g:
+    pass
+else:
+    pass
+
+p = +a + -b - ~c * d / e**f
+q = not (a and b) or c
+r = a & b | c ^ d
+
+s = a.b.c
+t = a[b][c, d][e:f]
+u = a(b)(c=d)

tests/cases/python-parser/04_all_syntax.py.ref.json

@@ -0,0 +1,725 @@
+{
+  "stmts": [
+    {
+      "_type": "ImportStmt",
+      "imports": [
+        {
+          "_type": "ImportAlias",
+          "name": "module1",
+          "alias": null
+        }
+      ]
+    },
+    {
+      "_type": "ImportStmt",
+      "imports": [
+        {
+          "_type": "ImportAlias",
+          "name": "module2",
+          "alias": "alias2"
+        }
+      ]
+    },
+    {
+      "_type": "FromImportStmt",
+      "module": "module3",
+      "imports": [
+        {
+          "_type": "ImportAlias",
+          "name": "submodule3",
+          "alias": null
+        }
+      ],
+      "level": 0
+    },
+    {
+      "_type": "FromImportStmt",
+      "module": "module4",
+      "imports": [
+        {
+          "_type": "ImportAlias",
+          "name": "submodule4",
+          "alias": "alias4"
+        }
+      ],
+      "level": 0
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "a",
+      "type": {
+        "_type": "BaseType",
+        "base": "int",
+        "args": []
+      }
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "b",
+      "type": {
+        "_type": "BaseType",
+        "base": "Generic",
+        "args": [
+          {
+            "_type": "BaseType",
+            "base": "int",
+            "args": []
+          }
+        ]
+      }
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "c",
+      "type": {
+        "_type": "BaseType",
+        "base": "Generic2",
+        "args": [
+          {
+            "_type": "BaseType",
+            "base": "int",
+            "args": []
+          },
+          {
+            "_type": "BaseType",
+            "base": "float",
+            "args": []
+          }
+        ]
+      }
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "d",
+      "type": {
+        "_type": "FrameType",
+        "columns": [
+          {
+            "_type": "FrameColumn",
+            "name": "a",
+            "type": {
+              "_type": "BaseType",
+              "base": "int",
+              "args": []
+            }
+          },
+          {
+            "_type": "FrameColumn",
+            "name": "b",
+            "type": {
+              "_type": "BaseType",
+              "base": "float",
+              "args": []
+            }
+          }
+        ]
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "e"
+        }
+      ],
+      "value": {
+        "_type": "LiteralExpr",
+        "value": 3
+      }
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "f",
+      "type": {
+        "_type": "BaseType",
+        "base": "int",
+        "args": []
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "f"
+        }
+      ],
+      "value": {
+        "_type": "LiteralExpr",
+        "value": 4
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "g"
+        }
+      ],
+      "value": {
+        "_type": "ListExpr",
+        "items": []
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "h"
+        }
+      ],
+      "value": {
+        "_type": "ListExpr",
+        "items": [
+          {
+            "_type": "LiteralExpr",
+            "value": 1
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": 0.1
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": " "
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": null
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": false
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": true
+          }
+        ]
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "i"
+        }
+      ],
+      "value": {
+        "_type": "DictExpr",
+        "keys": [],
+        "values": []
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "j"
+        }
+      ],
+      "value": {
+        "_type": "DictExpr",
+        "keys": [
+          {
+            "_type": "LiteralExpr",
+            "value": "a"
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": "b"
+          }
+        ],
+        "values": [
+          {
+            "_type": "LiteralExpr",
+            "value": 1
+          },
+          {
+            "_type": "LiteralExpr",
+            "value": 2
+          }
+        ]
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "k"
+        }
+      ],
+      "value": {
+        "_type": "DictExpr",
+        "keys": [
+          {
+            "_type": "LiteralExpr",
+            "value": "c"
+          },
+          null
+        ],
+        "values": [
+          {
+            "_type": "LiteralExpr",
+            "value": 3
+          },
+          {
+            "_type": "VariableExpr",
+            "name": "j"
+          }
+        ]
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "l"
+        }
+      ],
+      "value": {
+        "_type": "CastExpr",
+        "type": {
+          "_type": "BaseType",
+          "base": "int",
+          "args": []
+        },
+        "expr": {
+          "_type": "VariableExpr",
+          "name": "a"
+        },
+        "unsafe": false
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "m"
+        }
+      ],
+      "value": {
+        "_type": "CastExpr",
+        "type": {
+          "_type": "BaseType",
+          "base": "int",
+          "args": []
+        },
+        "expr": {
+          "_type": "VariableExpr",
+          "name": "a"
+        },
+        "unsafe": true
+      }
+    },
+    {
+      "_type": "Function",
+      "name": "n",
+      "params": {
+        "_type": "ParamSpec",
+        "pos": [
+          {
+            "name": "a",
+            "type": {
+              "_type": "BaseType",
+              "base": "int",
+              "args": []
+            },
+            "default": null
+          }
+        ],
+        "mixed": [
+          {
+            "name": "b",
+            "type": {
+              "_type": "BaseType",
+              "base": "float",
+              "args": []
+            },
+            "default": null
+          }
+        ],
+        "kw": [
+          {
+            "name": "c",
+            "type": {
+              "_type": "BaseType",
+              "base": "str",
+              "args": []
+            },
+            "default": null
+          }
+        ]
+      },
+      "returns": {
+        "_type": "BaseType",
+        "base": "Any",
+        "args": []
+      },
+      "body": [
+        {
+          "_type": "ReturnStmt",
+          "value": null
+        }
+      ]
+    },
+    {
+      "_type": "Function",
+      "name": "o",
+      "params": {
+        "_type": "ParamSpec",
+        "pos": [
+          {
+            "name": "a",
+            "type": {
+              "_type": "BaseType",
+              "base": "int",
+              "args": []
+            },
+            "default": {
+              "_type": "LiteralExpr",
+              "value": 1
+            }
+          }
+        ],
+        "mixed": [
+          {
+            "name": "b",
+            "type": {
+              "_type": "BaseType",
+              "base": "float",
+              "args": []
+            },
+            "default": {
+              "_type": "LiteralExpr",
+              "value": 2.0
+            }
+          }
+        ],
+        "kw": [
+          {
+            "name": "c",
+            "type": {
+              "_type": "BaseType",
+              "base": "str",
+              "args": []
+            },
+            "default": {
+              "_type": "LiteralExpr",
+              "value": ""
+            }
+          }
+        ]
+      },
+      "returns": {
+        "_type": "BaseType",
+        "base": "Any",
+        "args": []
+      },
+      "body": [
+        {
+          "_type": "ReturnStmt",
+          "value": {
+            "_type": "LiteralExpr",
+            "value": 1
+          }
+        }
+      ]
+    },
+    {
+      "_type": "ForStmt",
+      "target": {
+        "_type": "VariableExpr",
+        "name": "i"
+      },
+      "iterator": {
+        "_type": "VariableExpr",
+        "name": "h"
+      },
+      "body": []
+    },
+    {
+      "_type": "IfStmt",
+      "test": {
+        "_type": "CompareExpr",
+        "left": {
+          "_type": "VariableExpr",
+          "name": "e"
+        },
+        "operator": "==",
+        "right": {
+          "_type": "VariableExpr",
+          "name": "f"
+        }
+      },
+      "body": [],
+      "orelse": [
+        {
+          "_type": "IfStmt",
+          "test": {
+            "_type": "CompareExpr",
+            "left": {
+              "_type": "VariableExpr",
+              "name": "f"
+            },
+            "operator": "==",
+            "right": {
+              "_type": "VariableExpr",
+              "name": "g"
+            }
+          },
+          "body": [],
+          "orelse": []
+        }
+      ]
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "p"
+        }
+      ],
+      "value": {
+        "_type": "BinaryExpr",
+        "left": {
+          "_type": "BinaryExpr",
+          "left": {
+            "_type": "UnaryExpr",
+            "operator": "+",
+            "right": {
+              "_type": "VariableExpr",
+              "name": "a"
+            }
+          },
+          "operator": "+",
+          "right": {
+            "_type": "UnaryExpr",
+            "operator": "-",
+            "right": {
+              "_type": "VariableExpr",
+              "name": "b"
+            }
+          }
+        },
+        "operator": "-",
+        "right": {
+          "_type": "BinaryExpr",
+          "left": {
+            "_type": "BinaryExpr",
+            "left": {
+              "_type": "UnaryExpr",
+              "operator": "~",
+              "right": {
+                "_type": "VariableExpr",
+                "name": "c"
+              }
+            },
+            "operator": "*",
+            "right": {
+              "_type": "VariableExpr",
+              "name": "d"
+            }
+          },
+          "operator": "/",
+          "right": {
+            "_type": "BinaryExpr",
+            "left": {
+              "_type": "VariableExpr",
+              "name": "e"
+            },
+            "operator": "**",
+            "right": {
+              "_type": "VariableExpr",
+              "name": "f"
+            }
+          }
+        }
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "q"
+        }
+      ],
+      "value": {
+        "_type": "LogicalExpr",
+        "left": {
+          "_type": "UnaryExpr",
+          "operator": "not",
+          "right": {
+            "_type": "LogicalExpr",
+            "left": {
+              "_type": "VariableExpr",
+              "name": "a"
+            },
+            "operator": "and",
+            "right": {
+              "_type": "VariableExpr",
+              "name": "b"
+            }
+          }
+        },
+        "operator": "or",
+        "right": {
+          "_type": "VariableExpr",
+          "name": "c"
+        }
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "r"
+        }
+      ],
+      "value": {
+        "_type": "BinaryExpr",
+        "left": {
+          "_type": "BinaryExpr",
+          "left": {
+            "_type": "VariableExpr",
+            "name": "a"
+          },
+          "operator": "&",
+          "right": {
+            "_type": "VariableExpr",
+            "name": "b"
+          }
+        },
+        "operator": "|",
+        "right": {
+          "_type": "BinaryExpr",
+          "left": {
+            "_type": "VariableExpr",
+            "name": "c"
+          },
+          "operator": "^",
+          "right": {
+            "_type": "VariableExpr",
+            "name": "d"
+          }
+        }
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "s"
+        }
+      ],
+      "value": {
+        "_type": "GetExpr",
+        "object": {
+          "_type": "GetExpr",
+          "object": {
+            "_type": "VariableExpr",
+            "name": "a"
+          },
+          "name": "b"
+        },
+        "name": "c"
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "t"
+        }
+      ],
+      "value": {
+        "_type": "SubscriptExpr",
+        "object": {
+          "_type": "SubscriptExpr",
+          "object": {
+            "_type": "SubscriptExpr",
+            "object": {
+              "_type": "VariableExpr",
+              "name": "a"
+            },
+            "index": {
+              "_type": "VariableExpr",
+              "name": "b"
+            }
+          },
+          "index": {
+            "_type": "TupleExpr",
+            "items": [
+              {
+                "_type": "VariableExpr",
+                "name": "c"
+              },
+              {
+                "_type": "VariableExpr",
+                "name": "d"
+              }
+            ]
+          }
+        },
+        "index": {
+          "_type": "SliceExpr",
+          "lower": {
+            "_type": "VariableExpr",
+            "name": "e"
+          },
+          "upper": {
+            "_type": "VariableExpr",
+            "name": "f"
+          },
+          "step": null
+        }
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "u"
+        }
+      ],
+      "value": {
+        "_type": "CallExpr",
+        "callee": {
+          "_type": "CallExpr",
+          "callee": {
+            "_type": "VariableExpr",
+            "name": "a"
+          },
+          "arguments": [
+            {
+              "_type": "VariableExpr",
+              "name": "b"
+            }
+          ],
+          "keywords": {}
+        },
+        "arguments": [],
+        "keywords": {
+          "c": {
+            "_type": "VariableExpr",
+            "name": "d"
+          }
+        }
+      }
+    }
+  ]
+}

tests/checker.py

@@ -1,3 +1,4 @@
+import ast
 import json
 from dataclasses import asdict, dataclass, field
 from pathlib import Path
@@ -6,17 +7,30 @@ import midas.ast.python as p
 from midas.checker.checker import TypeChecker
 from midas.checker.diagnostic import Diagnostic
 from midas.checker.types import Type
+from midas.lexer.token import TokenType
 from tests.base import Tester
 from tests.serializer.python import PythonAstJsonSerializer
 
 
+class CustomEncoder(json.JSONEncoder):
+    def default(self, o):
+        if isinstance(o, ast.AST):
+            return ast.dump(o)
+        if isinstance(o, TokenType):
+            return o.name
+        if o == ...:
+            return "..."
+
+        return super().default(o)
+
+
 @dataclass
 class CaseResult:
     diagnostics: list[dict] = field(default_factory=list)
     judgments: list = field(default_factory=list)
 
     def dumps(self) -> str:
-        return json.dumps(asdict(self), indent=2)
+        return json.dumps(asdict(self), indent=2, cls=CustomEncoder)
 
 
 class CheckerTester(Tester):

tests/generator.py

@@ -3,7 +3,6 @@ from dataclasses import dataclass
 from pathlib import Path
 
 from midas.checker.checker import TypeChecker
-from midas.checker.diagnostic import DiagnosticType
 from midas.generator.generator import Generator
 from midas.utils import TypedAST
 from tests.base import Tester
@@ -44,7 +43,8 @@ class GeneratorTester(Tester):
 
         typed_ast: TypedAST = checker.type_check(path)
 
-        if not any(d.type == DiagnosticType.ERROR for d in checker.diagnostics):
+        # Ignore errors and generate anyway, easier here and errors should be
+        # covered by checker tests
         generator = Generator(workdir=path.parent, types=checker.types)
         generator.set_src_path(path)
         result.compiled_ast = generator.generate_ast(typed_ast)

tests/serializer/midas.py

@@ -1,4 +1,4 @@
-from typing import Optional, Sequence
+from typing import Optional, Sequence, final
 
 from midas.ast.midas import (
     AliasStmt,
@@ -28,6 +28,7 @@ from midas.ast.midas import (
 )
 
 
+@final
 class MidasAstJsonSerializer(
     Stmt.Visitor[dict], Expr.Visitor[dict], Type.Visitor[dict]
 ):

tests/serializer/python.py

@@ -1,5 +1,5 @@
 import ast
-from typing import Optional, Sequence, Type
+from typing import Optional, Sequence, Type, final
 
 from midas.ast.python import (
     AssignStmt,
@@ -78,6 +78,7 @@ boolean_ops: dict[Type[ast.boolop], str] = {
 }
 
 
+@final
 class PythonAstJsonSerializer(
     Stmt.Visitor[dict], Expr.Visitor[dict], MidasType.Visitor[dict]
 ):