fix(gen): handle TypeVar variance in stubs generator

midas/cli/highlighter.py

@@ -228,6 +228,13 @@ class PythonHighlighter(
         for item in expr.items:
             item.accept(self)
 
+    def visit_dict_expr(self, expr: p.DictExpr) -> None:
+        for key in expr.keys:
+            if key is not None:
+                key.accept(self)
+        for value in expr.values:
+            value.accept(self)
+
     def visit_subscript_expr(self, expr: p.SubscriptExpr) -> None:
         expr.object.accept(self)
         expr.index.accept(self)
@@ -240,6 +247,10 @@ class PythonHighlighter(
         if expr.step is not None:
             expr.step.accept(self)
 
+    def visit_raw_expr(self, expr: p.RawExpr) -> None: ...
+
+    def visit_raw_stmt(self, stmt: p.RawStmt) -> None: ...
+
 
 class MidasHighlighter(
     Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[None]
@@ -266,8 +277,9 @@ class MidasHighlighter(
     def visit_predicate_stmt(self, stmt: m.PredicateStmt) -> None:
         self.wrap(stmt, "predicate")
         self.wrap(LocatableToken(stmt.name), "predicate-name")
-        stmt.type.accept(self)
+        for spec in stmt.params:
-        stmt.condition.accept(self)
+            self._visit_param_spec(spec)
+        stmt.body.accept(self)
 
     def visit_logical_expr(self, expr: m.LogicalExpr) -> None:
         self.wrap(expr, "logical-expr")
@@ -283,6 +295,14 @@ class MidasHighlighter(
         self.wrap(expr, "unary-expr")
         expr.right.accept(self)
 
+    def visit_call_expr(self, expr: m.CallExpr) -> None:
+        self.wrap(expr, "call-expr")
+        expr.callee.accept(self)
+        for arg in expr.arguments:
+            arg.accept(self)
+        for arg in expr.keywords.values():
+            arg.accept(self)
+
     def visit_get_expr(self, expr: m.GetExpr) -> None:
         self.wrap(expr, "get-expr")
         expr.expr.accept(self)
@@ -318,8 +338,7 @@ class MidasHighlighter(
 
     def visit_function_type(self, type: m.FunctionType) -> None:
         self.wrap(type, "function")
-        for arg in type.pos_args + type.args + type.kw_args:
+        self._visit_param_spec(type.params)
-            arg.type.accept(self)
         type.returns.accept(self)
 
     def visit_extension_type(self, type: m.ExtensionType) -> None:
@@ -327,6 +346,10 @@ class MidasHighlighter(
         type.base.accept(self)
         type.extension.accept(self)
 
+    def _visit_param_spec(self, spec: m.ParamSpec) -> None:
+        for param in spec.pos + spec.mixed + spec.kw:
+            param.type.accept(self)
+
 
 class DiagnosticsHighlighter(Highlighter):
     EXTRA_CSS_PATH: Optional[Path] = Path(__file__).parent / "hl_diagnostic.css"

midas/generator/stubs.py

@@ -1,5 +1,5 @@
 import ast
-from typing import Optional
+from typing import Optional, assert_never
 
 import midas.ast.midas as m
 from midas.checker.registry import Member, TypesRegistry
@@ -8,6 +8,7 @@ from midas.checker.types import (
     AppliedType,
     BaseType,
     ComplexType,
+    ConstraintType,
     ExtensionType,
     Function,
     GenericType,
@@ -17,6 +18,7 @@ from midas.checker.types import (
     TypeVar,
     UnitType,
     UnknownType,
+    Variance,
     substitute_typevars,
 )
 
@@ -84,6 +86,7 @@ class StubsGenerator:
         match type:
             case AliasType(type=base):
                 return [self.dump_type(base)], {}
+
             case GenericType(params=params, body=body):
                 self.add_typing_import("Generic")
                 type_vars: ast.expr
@@ -111,6 +114,7 @@ class StubsGenerator:
                     ],
                     body_subsitutions | substitutions,
                 )
+
             case _:
                 return [], {}
 
@@ -148,15 +152,20 @@ class StubsGenerator:
             case TopType() | UnknownType():
                 self.add_typing_import("Any")
                 return ast.Name(id="Any")
+
             case BaseType(name=name):
                 return ast.Name(id=name)
+
             case AliasType(name=name):
                 return ast.Name(id=name)
+
             case UnitType():
                 return ast.Constant(value=None)
+
             case Function():
                 name: str = self.define_protocol(type)
                 return ast.Name(id=name)
+
             case OverloadedFunction(overloads=overloads):
                 if len(overloads) == 1:
                     return self.dump_type(overloads[0])
@@ -176,6 +185,7 @@ class StubsGenerator:
 
             case TypeVar():
                 return ast.Name(id=type.name)
+
             case GenericType(name=name):
                 params: ast.expr
                 if len(type.params) == 1:
@@ -188,6 +198,7 @@ class StubsGenerator:
                     value=ast.Name(id=type.name),
                     slice=params,
                 )
+
             case AppliedType():
                 args: ast.expr
                 if len(type.args) == 1:
@@ -199,6 +210,12 @@ class StubsGenerator:
                     slice=args,
                 )
 
+            case ConstraintType():
+                return self.dump_type(type.type)
+
+            case _:
+                assert_never(type)
+
     def dump_method(
         self, name: str, method: Type, overloaded: bool = False
     ) -> list[ast.stmt]:
@@ -313,6 +330,29 @@ class StubsGenerator:
     def define_type_var(self, var: TypeVar) -> TypeVar:
         name: str = self.new_type_var_name()
         self.add_typing_import("TypeVar")
+
+        kwargs: list[ast.keyword] = []
+        if var.bound is not None:
+            kwargs.append(
+                ast.keyword(
+                    arg="bound",
+                    value=self.dump_type(var.bound),
+                )
+            )
+        if var.variance == Variance.COVARIANT:
+            kwargs.append(
+                ast.keyword(
+                    arg="covariant",
+                    value=ast.Constant(value=True),
+                )
+            )
+        elif var.variance == Variance.CONTRAVARIANT:
+            kwargs.append(
+                ast.keyword(
+                    arg="contravariant",
+                    value=ast.Constant(value=True),
+                )
+            )
         self.add_stub(
             ast.Assign(
                 targets=[ast.Name(id=name)],
@@ -321,16 +361,7 @@ class StubsGenerator:
                     args=[
                         ast.Constant(value=name),
                     ],
-                    keywords=(
+                    keywords=kwargs,
-                        []
-                        if var.bound is None
-                        else [
-                            ast.keyword(
-                                arg="bound",
-                                value=self.dump_type(var.bound),
-                            )
-                        ]
-                    ),
                 ),
             )
         )