feat: add helpful info to internal AssertionError excs (#19404)

I added some contextual information to various assert statements
throughout the repo.

This information is helpful for me while debugging [Issue
1116](mypyc/mypyc#1116) and should be
similarly useful in many other debugging contexts.

Author: BobTheBuidler

mypy/checker.py

@@ -7273,7 +7273,7 @@ def named_type(self, name: str) -> Instance:
         if isinstance(node, TypeAlias):
             assert isinstance(node.target, Instance)  # type: ignore[misc]
             node = node.target.type
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         any_type = AnyType(TypeOfAny.from_omitted_generics)
         return Instance(node, [any_type] * len(node.defn.type_vars))
 
@@ -7292,7 +7292,7 @@ def lookup_typeinfo(self, fullname: str) -> TypeInfo:
         # Assume that the name refers to a class.
         sym = self.lookup_qualified(fullname)
         node = sym.node
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         return node
 
     def type_type(self) -> Instance:

mypy/checkpattern.py

@@ -796,9 +796,9 @@ def get_var(expr: Expression) -> Var:
     Warning: this in only true for expressions captured by a match statement.
     Don't call it from anywhere else
     """
-    assert isinstance(expr, NameExpr)
+    assert isinstance(expr, NameExpr), expr
     node = expr.node
-    assert isinstance(node, Var)
+    assert isinstance(node, Var), node
     return node
 
 

mypy/plugins/attrs.py

@@ -458,7 +458,7 @@ def _analyze_class(
             if isinstance(node, PlaceholderNode):
                 # This node is not ready yet.
                 continue
-            assert isinstance(node, Var)
+            assert isinstance(node, Var), node
             node.is_initialized_in_class = False
 
     # Traverse the MRO and collect attributes from the parents.

mypy/plugins/dataclasses.py

@@ -610,7 +610,7 @@ def collect_attributes(self) -> list[DataclassAttribute] | None:
                 # We will issue an error later.
                 continue
 
-            assert isinstance(node, Var)
+            assert isinstance(node, Var), node
 
             # x: ClassVar[int] is ignored by dataclasses.
             if node.is_classvar:

mypy/semanal.py

@@ -6630,7 +6630,7 @@ def named_type(self, fullname: str, args: list[Type] | None = None) -> Instance:
         sym = self.lookup_fully_qualified(fullname)
         assert sym, "Internal error: attempted to construct unknown type"
         node = sym.node
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         if args:
             # TODO: assert len(args) == len(node.defn.type_vars)
             return Instance(node, args)

mypy/semanal_main.py

@@ -290,7 +290,7 @@ def process_functions(graph: Graph, scc: list[str], patches: Patches) -> None:
 
     for module, target, node, active_type in order_by_subclassing(all_targets):
         analyzer = graph[module].manager.semantic_analyzer
-        assert isinstance(node, (FuncDef, OverloadedFuncDef, Decorator))
+        assert isinstance(node, (FuncDef, OverloadedFuncDef, Decorator)), node
         process_top_level_function(
             analyzer, graph[module], module, target, node, active_type, patches
         )

mypyc/analysis/attrdefined.py

@@ -285,15 +285,15 @@ def mark_attr_initialization_ops(
 def attributes_initialized_by_init_call(op: Call) -> set[str]:
     """Calculate attributes that are always initialized by a super().__init__ call."""
     self_type = op.fn.sig.args[0].type
-    assert isinstance(self_type, RInstance)
+    assert isinstance(self_type, RInstance), self_type
     cl = self_type.class_ir
     return {a for base in cl.mro for a in base.attributes if base.is_always_defined(a)}
 
 
 def attributes_maybe_initialized_by_init_call(op: Call) -> set[str]:
     """Calculate attributes that may be initialized by a super().__init__ call."""
     self_type = op.fn.sig.args[0].type
-    assert isinstance(self_type, RInstance)
+    assert isinstance(self_type, RInstance), self_type
     cl = self_type.class_ir
     return attributes_initialized_by_init_call(op) | cl._sometimes_initialized_attrs
 

mypyc/analysis/selfleaks.py

@@ -92,7 +92,7 @@ def visit_call(self, op: Call) -> GenAndKill:
         fn = op.fn
         if fn.class_name and fn.name == "__init__":
             self_type = op.fn.sig.args[0].type
-            assert isinstance(self_type, RInstance)
+            assert isinstance(self_type, RInstance), self_type
             cl = self_type.class_ir
             if not cl.init_self_leak:
                 return CLEAN

mypyc/codegen/emit.py

@@ -742,7 +742,7 @@ def emit_cast_error_handler(
             self.emit_traceback(error.source_path, error.module_name, error.traceback_entry)
             self.emit_line("goto %s;" % error.label)
         else:
-            assert isinstance(error, ReturnHandler)
+            assert isinstance(error, ReturnHandler), error
             self.emit_line("return %s;" % error.value)
 
     def emit_union_cast(
@@ -871,7 +871,7 @@ def emit_unbox(
         elif isinstance(error, GotoHandler):
             failure = "goto %s;" % error.label
         else:
-            assert isinstance(error, ReturnHandler)
+            assert isinstance(error, ReturnHandler), error
             failure = "return %s;" % error.value
         if raise_exception:
             raise_exc = f'CPy_TypeError("{self.pretty_name(typ)}", {src}); '

mypyc/codegen/emitfunc.py

@@ -160,7 +160,7 @@ def generate_native_function(
     # eliminated during code generation.
     for block in fn.blocks:
         terminator = block.terminator
-        assert isinstance(terminator, ControlOp)
+        assert isinstance(terminator, ControlOp), terminator
 
         for target in terminator.targets():
             is_next_block = target.label == block.label + 1
@@ -309,7 +309,7 @@ def visit_assign(self, op: Assign) -> None:
 
     def visit_assign_multi(self, op: AssignMulti) -> None:
         typ = op.dest.type
-        assert isinstance(typ, RArray)
+        assert isinstance(typ, RArray), typ
         dest = self.reg(op.dest)
         # RArray values can only be assigned to once, so we can always
         # declare them on initialization.
@@ -586,7 +586,7 @@ def visit_method_call(self, op: MethodCall) -> None:
     def emit_method_call(self, dest: str, op_obj: Value, name: str, op_args: list[Value]) -> None:
         obj = self.reg(op_obj)
         rtype = op_obj.type
-        assert isinstance(rtype, RInstance)
+        assert isinstance(rtype, RInstance), rtype
         class_ir = rtype.class_ir
         method = rtype.class_ir.get_method(name)
         assert method is not None
@@ -805,7 +805,7 @@ def visit_get_element_ptr(self, op: GetElementPtr) -> None:
         dest = self.reg(op)
         src = self.reg(op.src)
         # TODO: support tuple type
-        assert isinstance(op.src_type, RStruct)
+        assert isinstance(op.src_type, RStruct), op.src_type
         assert op.field in op.src_type.names, "Invalid field name."
         self.emit_line(
             "{} = ({})&(({} *){})->{};".format(