diff --git a/artiq/compiler/asttyped.py b/artiq/compiler/asttyped.py
index f15726579..c9e543ae2 100644
--- a/artiq/compiler/asttyped.py
+++ b/artiq/compiler/asttyped.py
@@ -25,15 +25,15 @@ class scoped(object):
 class argT(ast.arg, commontyped):
     pass
 
-class ClassDefT(ast.ClassDef, scoped):
-    pass
+class ClassDefT(ast.ClassDef):
+    _types = ("constructor_type",)
 class FunctionDefT(ast.FunctionDef, scoped):
     _types = ("signature_type",)
 class ModuleT(ast.Module, scoped):
     pass
 
 class ExceptHandlerT(ast.ExceptHandler):
-    _fields = ("filter", "name", "body") # rename ast.ExceptHandler.type
+    _fields = ("filter", "name", "body") # rename ast.ExceptHandler.type to filter
     _types = ("name_type",)
 
 class SliceT(ast.Slice, commontyped):
diff --git a/artiq/compiler/builtins.py b/artiq/compiler/builtins.py
index c34ccf126..60c7af718 100644
--- a/artiq/compiler/builtins.py
+++ b/artiq/compiler/builtins.py
@@ -96,44 +96,32 @@ class TException(types.TMono):
     def __init__(self, name="Exception"):
         super().__init__(name)
 
-class TIndexError(TException):
-    def __init__(self):
-        super().__init__("IndexError")
-
-class TValueError(TException):
-    def __init__(self):
-        super().__init__("ValueError")
-
-class TZeroDivisionError(TException):
-    def __init__(self):
-        super().__init__("ZeroDivisionError")
-
 def fn_bool():
-    return types.TConstructor("bool")
+    return types.TConstructor(TBool())
 
 def fn_int():
-    return types.TConstructor("int")
+    return types.TConstructor(TInt())
 
 def fn_float():
-    return types.TConstructor("float")
+    return types.TConstructor(TFloat())
 
 def fn_str():
-    return types.TConstructor("str")
+    return types.TConstructor(TStr())
 
 def fn_list():
-    return types.TConstructor("list")
+    return types.TConstructor(TList())
 
 def fn_Exception():
-    return types.TExceptionConstructor("Exception")
+    return types.TExceptionConstructor(TException("Exception"))
 
 def fn_IndexError():
-    return types.TExceptionConstructor("IndexError")
+    return types.TExceptionConstructor(TException("IndexError"))
 
 def fn_ValueError():
-    return types.TExceptionConstructor("ValueError")
+    return types.TExceptionConstructor(TException("ValueError"))
 
 def fn_ZeroDivisionError():
-    return types.TExceptionConstructor("ZeroDivisionError")
+    return types.TExceptionConstructor(TException("ZeroDivisionError"))
 
 def fn_range():
     return types.TBuiltinFunction("range")
@@ -215,4 +203,4 @@ def is_collection(typ):
 def is_allocated(typ):
     return typ.fold(False, lambda accum, typ:
         is_list(typ) or is_str(typ) or types.is_function(typ) or
-        is_exception(typ))
+        is_exception(typ) or types.is_constructor(typ))
diff --git a/artiq/compiler/ir.py b/artiq/compiler/ir.py
index 2561d4ea4..0f3ca3131 100644
--- a/artiq/compiler/ir.py
+++ b/artiq/compiler/ir.py
@@ -636,9 +636,9 @@ class SetAttr(Instruction):
         assert isinstance(attr, (str, int))
         assert isinstance(value, Value)
         if isinstance(attr, int):
-            assert value.type == obj.type.elts[attr]
+            assert value.type == obj.type.elts[attr].find()
         else:
-            assert value.type == obj.type.attributes[attr]
+            assert value.type == obj.type.attributes[attr].find()
         super().__init__([obj, value], builtins.TNone(), name)
         self.attr = attr
 
diff --git a/artiq/compiler/transforms/artiq_ir_generator.py b/artiq/compiler/transforms/artiq_ir_generator.py
index a822f8815..01fd558b2 100644
--- a/artiq/compiler/transforms/artiq_ir_generator.py
+++ b/artiq/compiler/transforms/artiq_ir_generator.py
@@ -73,6 +73,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
         self.name = [module_name] if module_name != "" else []
         self.current_loc = None
         self.current_function = None
+        self.current_class = None
         self.current_globals = set()
         self.current_block = None
         self.current_env = None
@@ -156,6 +157,17 @@ class ARTIQIRGenerator(algorithm.Visitor):
 
     # Statement visitors
 
+    def visit_ClassDefT(self, node):
+        klass = self.append(ir.Alloc([], node.constructor_type,
+                                     name="class.{}".format(node.name)))
+        self._set_local(node.name, klass)
+
+        try:
+            old_class, self.current_class = self.current_class, klass
+            self.visit(node.body)
+        finally:
+            self.current_class = old_class
+
     def visit_function(self, node, is_lambda, is_internal):
         if is_lambda:
             name = "lambda@{}:{}".format(node.loc.line(), node.loc.column())
@@ -239,9 +251,12 @@ class ARTIQIRGenerator(algorithm.Visitor):
 
         return self.append(ir.Closure(func, self.current_env))
 
-    def visit_FunctionDefT(self, node):
+    def visit_FunctionDefT(self, node, in_class=None):
         func = self.visit_function(node, is_lambda=False, is_internal=len(self.name) > 2)
-        self._set_local(node.name, func)
+        if in_class is None:
+            self._set_local(node.name, func)
+        else:
+            self.append(ir.SetAttr(in_class, node.name, func))
 
     def visit_Return(self, node):
         if node.value is None:
@@ -668,9 +683,19 @@ class ARTIQIRGenerator(algorithm.Visitor):
             return self.current_env
 
     def _get_local(self, name):
-        return self.append(ir.GetLocal(self._env_for(name), name, name="local." + name))
+        if self.current_class is not None and \
+                name in self.current_class.type.attributes:
+            return self.append(ir.GetAttr(self.current_class, name,
+                                          name="local." + name))
+
+        return self.append(ir.GetLocal(self._env_for(name), name,
+                                       name="local." + name))
 
     def _set_local(self, name, value):
+        if self.current_class is not None and \
+                name in self.current_class.type.attributes:
+            return self.append(ir.SetAttr(self.current_class, name, value))
+
         self.append(ir.SetLocal(self._env_for(name), name, value))
 
     def visit_NameT(self, node):
@@ -706,7 +731,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
         head = self.current_block
 
         self.current_block = out_of_bounds_block = self.add_block()
-        exn = self.alloc_exn(builtins.TIndexError(),
+        exn = self.alloc_exn(builtins.TException("IndexError"),
             ir.Constant("index {0} out of bounds 0:{1}", builtins.TStr()),
             index, length)
         self.raise_exn(exn, loc=loc)
@@ -790,7 +815,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
                 step = self.visit(node.slice.step)
                 self._make_check(
                     self.append(ir.Compare(ast.NotEq(loc=None), step, ir.Constant(0, step.type))),
-                    lambda: self.alloc_exn(builtins.TValueError(),
+                    lambda: self.alloc_exn(builtins.TException("ValueError"),
                         ir.Constant("step cannot be zero", builtins.TStr())),
                     loc=node.slice.step.loc)
             else:
@@ -811,7 +836,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
                                                name="slice.size"))
             self._make_check(
                 self.append(ir.Compare(ast.LtE(loc=None), slice_size, length)),
-                lambda: self.alloc_exn(builtins.TValueError(),
+                lambda: self.alloc_exn(builtins.TException("ValueError"),
                     ir.Constant("slice size {0} is larger than iterable length {1}",
                                 builtins.TStr()),
                     slice_size, length),
@@ -894,7 +919,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
             self._make_check(
                 self.append(ir.Compare(ast.Eq(loc=None), length,
                                        ir.Constant(len(node.elts), self._size_type))),
-                lambda: self.alloc_exn(builtins.TValueError(),
+                lambda: self.alloc_exn(builtins.TException("ValueError"),
                     ir.Constant("list must be {0} elements long to decompose", builtins.TStr()),
                     length))
 
@@ -1002,13 +1027,13 @@ class ARTIQIRGenerator(algorithm.Visitor):
                 # Check for negative shift amount.
                 self._make_check(
                     self.append(ir.Compare(ast.GtE(loc=None), rhs, ir.Constant(0, rhs.type))),
-                    lambda: self.alloc_exn(builtins.TValueError(),
+                    lambda: self.alloc_exn(builtins.TException("ValueError"),
                         ir.Constant("shift amount must be nonnegative", builtins.TStr())),
                     loc=node.right.loc)
             elif isinstance(node.op, (ast.Div, ast.FloorDiv)):
                 self._make_check(
                     self.append(ir.Compare(ast.NotEq(loc=None), rhs, ir.Constant(0, rhs.type))),
-                    lambda: self.alloc_exn(builtins.TZeroDivisionError(),
+                    lambda: self.alloc_exn(builtins.TException("ZeroDivisionError"),
                         ir.Constant("cannot divide by zero", builtins.TStr())),
                     loc=node.right.loc)
 
diff --git a/artiq/compiler/transforms/asttyped_rewriter.py b/artiq/compiler/transforms/asttyped_rewriter.py
index 51b84efb0..5f02431c4 100644
--- a/artiq/compiler/transforms/asttyped_rewriter.py
+++ b/artiq/compiler/transforms/asttyped_rewriter.py
@@ -3,7 +3,8 @@
 to a typedtree (:mod:`..asttyped`).
 """
 
-from pythonparser import algorithm, diagnostic
+from collections import OrderedDict
+from pythonparser import ast, algorithm, diagnostic
 from .. import asttyped, types, builtins
 
 # This visitor will be called for every node with a scope,
@@ -16,7 +17,7 @@ class LocalExtractor(algorithm.Visitor):
 
         self.in_root    = False
         self.in_assign  = False
-        self.typing_env = {}
+        self.typing_env = OrderedDict()
 
         # which names are global have to be recorded in the current scope
         self.global_    = set()
@@ -189,6 +190,7 @@ class ASTTypedRewriter(algorithm.Transformer):
         self.engine = engine
         self.globals = None
         self.env_stack = [prelude]
+        self.in_class = None
 
     def _try_find_name(self, name):
         for typing_env in reversed(self.env_stack):
@@ -196,11 +198,17 @@ class ASTTypedRewriter(algorithm.Transformer):
                 return typing_env[name]
 
     def _find_name(self, name, loc):
+        if self.in_class is not None:
+            typ = self.in_class.constructor_type.attributes.get(name)
+            if typ is not None:
+                return typ
+
         typ = self._try_find_name(name)
         if typ is not None:
             return typ
+
         diag = diagnostic.Diagnostic("fatal",
-            "name '{name}' is not bound to anything", {"name":name}, loc)
+            "undefined variable '{name}'", {"name":name}, loc)
         self.engine.process(diag)
 
     # Visitors that replace node with a typed node
@@ -239,6 +247,66 @@ class ASTTypedRewriter(algorithm.Transformer):
         finally:
             self.env_stack.pop()
 
+    def visit_ClassDef(self, node):
+        if any(node.bases) or any(node.keywords) or \
+                node.starargs is not None or node.kwargs is not None:
+            diag = diagnostic.Diagnostic("error",
+                "inheritance is not supported", {},
+                node.lparen_loc.join(node.rparen_loc))
+            self.engine.process(diag)
+
+        for child in node.body:
+            if isinstance(child, (ast.Assign, ast.FunctionDef, ast.Pass)):
+                continue
+
+            diag = diagnostic.Diagnostic("fatal",
+                "class body must contain only assignments and function definitions", {},
+                child.loc)
+            self.engine.process(diag)
+
+        if node.name in self.env_stack[-1]:
+            diag = diagnostic.Diagnostic("fatal",
+                "variable '{name}' is already defined", {"name":name}, loc)
+            self.engine.process(diag)
+
+        extractor = LocalExtractor(env_stack=self.env_stack, engine=self.engine)
+        extractor.visit(node)
+
+        # Now we create two types.
+        # The first type is the type of instances created by the constructor.
+        # Its attributes are those of the class environment, but wrapped
+        # appropriately so that they are linked to the class from which they
+        # originate.
+        instance_type = types.TMono(node.name)
+        instance_type.attributes = OrderedDict({}) # TODO
+
+        # The second type is the type of the constructor itself (in other words,
+        # the class object): it is simply a singleton type that has the class
+        # environment as attributes.
+        constructor_type = types.TConstructor(instance_type)
+        constructor_type.attributes = extractor.typing_env
+
+        self.env_stack[-1][node.name] = constructor_type
+
+        node = asttyped.ClassDefT(
+            constructor_type=constructor_type,
+            name=node.name,
+            bases=self.visit(node.bases), keywords=self.visit(node.keywords),
+            starargs=self.visit(node.starargs), kwargs=self.visit(node.kwargs),
+            body=node.body,
+            decorator_list=self.visit(node.decorator_list),
+            keyword_loc=node.keyword_loc, name_loc=node.name_loc,
+            lparen_loc=node.lparen_loc, star_loc=node.star_loc,
+            dstar_loc=node.dstar_loc, rparen_loc=node.rparen_loc,
+            colon_loc=node.colon_loc, at_locs=node.at_locs,
+            loc=node.loc)
+
+        try:
+            old_in_class, self.in_class = self.in_class, node
+            return self.generic_visit(node)
+        finally:
+            self.in_class = old_in_class
+
     def visit_arg(self, node):
         return asttyped.argT(type=self._find_name(node.arg, node.loc),
                              arg=node.arg, annotation=self.visit(node.annotation),
@@ -426,7 +494,6 @@ class ASTTypedRewriter(algorithm.Transformer):
     visit_YieldFrom = visit_unsupported
 
     # stmt
-    visit_ClassDef = visit_unsupported
     visit_Delete = visit_unsupported
     visit_Import = visit_unsupported
     visit_ImportFrom = visit_unsupported
diff --git a/artiq/compiler/transforms/inferencer.py b/artiq/compiler/transforms/inferencer.py
index 0fe000189..5c906939d 100644
--- a/artiq/compiler/transforms/inferencer.py
+++ b/artiq/compiler/transforms/inferencer.py
@@ -467,7 +467,7 @@ class Inferencer(algorithm.Visitor):
             else:
                 diagnose(valid_forms())
 
-            self._unify(node.type, getattr(builtins, "T" + typ.name)(),
+            self._unify(node.type, typ.instance,
                         node.loc, None)
         elif types.is_builtin(typ, "bool"):
             valid_forms = lambda: [
@@ -895,38 +895,47 @@ class Inferencer(algorithm.Visitor):
                 "decorators are not supported", {},
                 node.at_locs[index], [decorator.loc])
             self.engine.process(diag)
-            return
 
-        old_function, self.function = self.function, node
-        old_in_loop, self.in_loop = self.in_loop, False
-        old_has_return, self.has_return = self.has_return, False
+        try:
+            old_function, self.function = self.function, node
+            old_in_loop, self.in_loop = self.in_loop, False
+            old_has_return, self.has_return = self.has_return, False
 
-        self.generic_visit(node)
+            self.generic_visit(node)
 
-        # Lack of return statements is not the only case where the return
-        # type cannot be inferred. The other one is infinite (possibly mutual)
-        # recursion. Since Python functions don't have to return a value,
-        # we ignore that one.
-        if not self.has_return:
-            def makenotes(printer, typea, typeb, loca, locb):
-                return [
-                    diagnostic.Diagnostic("note",
-                        "function with return type {typea}",
-                        {"typea": printer.name(typea)},
-                        node.name_loc),
-                ]
-            self._unify(node.return_type, builtins.TNone(),
-                        node.name_loc, None, makenotes)
-
-        self.function = old_function
-        self.in_loop = old_in_loop
-        self.has_return = old_has_return
+            # Lack of return statements is not the only case where the return
+            # type cannot be inferred. The other one is infinite (possibly mutual)
+            # recursion. Since Python functions don't have to return a value,
+            # we ignore that one.
+            if not self.has_return:
+                def makenotes(printer, typea, typeb, loca, locb):
+                    return [
+                        diagnostic.Diagnostic("note",
+                            "function with return type {typea}",
+                            {"typea": printer.name(typea)},
+                            node.name_loc),
+                    ]
+                self._unify(node.return_type, builtins.TNone(),
+                            node.name_loc, None, makenotes)
+        finally:
+            self.function = old_function
+            self.in_loop = old_in_loop
+            self.has_return = old_has_return
 
         signature_type = self._type_from_arguments(node.args, node.return_type)
         if signature_type:
             self._unify(node.signature_type, signature_type,
                         node.name_loc, None)
 
+    def visit_ClassDefT(self, node):
+        if any(node.decorator_list):
+            diag = diagnostic.Diagnostic("error",
+                "decorators are not supported", {},
+                node.at_locs[0], [node.decorator_list[0].loc])
+            self.engine.process(diag)
+
+        self.generic_visit(node)
+
     def visit_Return(self, node):
         if not self.function:
             diag = diagnostic.Diagnostic("error",
diff --git a/artiq/compiler/transforms/llvm_ir_generator.py b/artiq/compiler/transforms/llvm_ir_generator.py
index 4fd341763..5b2dfb929 100644
--- a/artiq/compiler/transforms/llvm_ir_generator.py
+++ b/artiq/compiler/transforms/llvm_ir_generator.py
@@ -437,7 +437,7 @@ class LLVMIRGenerator:
                                             size=llsize)
             llvalue = self.llbuilder.insert_value(llvalue, llalloc, 1, name=insn.name)
             return llvalue
-        elif builtins.is_exception(insn.type):
+        elif builtins.is_exception(insn.type) or types.is_constructor(insn.type):
             llalloc = self.llbuilder.alloca(self.llty_of_type(insn.type, bare=True))
             for index, operand in enumerate(insn.operands):
                 lloperand = self.map(operand)
diff --git a/artiq/compiler/types.py b/artiq/compiler/types.py
index 631a9107e..93b3b3d20 100644
--- a/artiq/compiler/types.py
+++ b/artiq/compiler/types.py
@@ -319,9 +319,17 @@ class TConstructor(TBuiltin):
     A type of a constructor of a builtin class, e.g. ``list``.
     Note that this is not the same as the type of an instance of
     the class, which is ``TMono("list", ...)``.
+
+    :ivar instance: (:class:`Type`)
+        the type of the instance created by this constructor
     """
 
-class TExceptionConstructor(TBuiltin):
+    def __init__(self, instance):
+        assert isinstance(instance, TMono)
+        super().__init__(instance.name)
+        self.instance = instance
+
+class TExceptionConstructor(TConstructor):
     """
     A type of a constructor of a builtin exception, e.g. ``Exception``.
     Note that this is not the same as the type of an instance of
@@ -402,6 +410,14 @@ def is_builtin(typ, name=None):
         return isinstance(typ, TBuiltin) and \
             typ.name == name
 
+def is_constructor(typ, name=None):
+    typ = typ.find()
+    if name is not None:
+        return isinstance(typ, TConstructor) and \
+            typ.name == name
+    else:
+        return isinstance(typ, TConstructor)
+
 def is_exn_constructor(typ, name=None):
     typ = typ.find()
     if name is not None:
@@ -459,9 +475,11 @@ class TypePrinter(object):
             elif isinstance(typ, TFunction):
                 return signature
         elif isinstance(typ, TBuiltinFunction):
-            return "<function %s>" % typ.name
+            return "<function {}>".format(typ.name)
         elif isinstance(typ, (TConstructor, TExceptionConstructor)):
-            return "<constructor %s>" % typ.name
+            attrs = ", ".join(["{}: {}".format(attr, self.name(typ.attributes[attr]))
+                               for attr in typ.attributes])
+            return "<constructor {} {{{}}}>".format(typ.name, attrs)
         elif isinstance(typ, TValue):
             return repr(typ.value)
         else:
diff --git a/artiq/compiler/validators/escape.py b/artiq/compiler/validators/escape.py
index df87c6afc..9fc053fe6 100644
--- a/artiq/compiler/validators/escape.py
+++ b/artiq/compiler/validators/escape.py
@@ -208,7 +208,7 @@ class EscapeValidator(algorithm.Visitor):
                     loc)
             ]
 
-    def visit_in_region(self, node, region):
+    def visit_in_region(self, node, region, typing_env):
         try:
             old_youngest_region = self.youngest_region
             self.youngest_region = region
@@ -216,8 +216,8 @@ class EscapeValidator(algorithm.Visitor):
             old_youngest_env = self.youngest_env
             self.youngest_env = {}
 
-            for name in node.typing_env:
-                if builtins.is_allocated(node.typing_env[name]):
+            for name in typing_env:
+                if builtins.is_allocated(typing_env[name]):
                     self.youngest_env[name] = Region(None) # not yet known
                 else:
                     self.youngest_env[name] = None # lives forever
@@ -230,11 +230,15 @@ class EscapeValidator(algorithm.Visitor):
             self.youngest_region = old_youngest_region
 
     def visit_ModuleT(self, node):
-        self.visit_in_region(node, None)
+        self.visit_in_region(node, None, node.typing_env)
 
     def visit_FunctionDefT(self, node):
         self.youngest_env[node.name] = self.youngest_region
-        self.visit_in_region(node, Region(node.loc))
+        self.visit_in_region(node, Region(node.loc), node.typing_env)
+
+    def visit_ClassDefT(self, node):
+        self.youngest_env[node.name] = self.youngest_region
+        self.visit_in_region(node, Region(node.loc), node.constructor_type.attributes)
 
     # Only three ways for a pointer to escape:
     #   * Assigning or op-assigning it (we ensure an outlives relationship)
diff --git a/lit-test/test/inferencer/builtin_calls.py b/lit-test/test/inferencer/builtin_calls.py
index 50597151f..1ba629fba 100644
--- a/lit-test/test/inferencer/builtin_calls.py
+++ b/lit-test/test/inferencer/builtin_calls.py
@@ -1,28 +1,28 @@
 # RUN: %python -m artiq.compiler.testbench.inferencer %s >%t
 # RUN: OutputCheck %s --file-to-check=%t
 
-# CHECK-L: bool:<constructor bool>():bool
+# CHECK-L: bool:<constructor bool {}>():bool
 bool()
 
-# CHECK-L: bool:<constructor bool>([]:list(elt='a)):bool
+# CHECK-L: bool:<constructor bool {}>([]:list(elt='a)):bool
 bool([])
 
-# CHECK-L: int:<constructor int>():int(width='b)
+# CHECK-L: int:<constructor int {}>():int(width='b)
 int()
 
-# CHECK-L: int:<constructor int>(1.0:float):int(width='c)
+# CHECK-L: int:<constructor int {}>(1.0:float):int(width='c)
 int(1.0)
 
-# CHECK-L: int:<constructor int>(1.0:float, width=64:int(width='d)):int(width=64)
+# CHECK-L: int:<constructor int {}>(1.0:float, width=64:int(width='d)):int(width=64)
 int(1.0, width=64)
 
-# CHECK-L: float:<constructor float>():float
+# CHECK-L: float:<constructor float {}>():float
 float()
 
-# CHECK-L: float:<constructor float>(1:int(width='e)):float
+# CHECK-L: float:<constructor float {}>(1:int(width='e)):float
 float(1)
 
-# CHECK-L: list:<constructor list>():list(elt='f)
+# CHECK-L: list:<constructor list {}>():list(elt='f)
 list()
 
 # CHECK-L: len:<function len>([]:list(elt='g)):int(width=32)
diff --git a/lit-test/test/inferencer/class.py b/lit-test/test/inferencer/class.py
new file mode 100644
index 000000000..4b14a2737
--- /dev/null
+++ b/lit-test/test/inferencer/class.py
@@ -0,0 +1,14 @@
+# RUN: %python -m artiq.compiler.testbench.inferencer %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+class c:
+    a = 1
+    def f():
+        pass
+
+# CHECK-L: c:<constructor c {a: int(width='a), f: ()->NoneType}>
+c
+# CHECK-L: .a:int(width='a)
+c.a
+# CHECK-L: .f:()->NoneType
+c.f
diff --git a/lit-test/test/inferencer/error_class.py b/lit-test/test/inferencer/error_class.py
new file mode 100644
index 000000000..0cc075b05
--- /dev/null
+++ b/lit-test/test/inferencer/error_class.py
@@ -0,0 +1,10 @@
+# RUN: %python -m artiq.compiler.testbench.inferencer +diag %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+# CHECK-L: ${LINE:+1}: error: inheritance is not supported
+class a(1):
+    pass
+
+class b:
+    # CHECK-L: ${LINE:+1}: fatal: class body must contain only assignments and function definitions
+    x += 1
diff --git a/lit-test/test/inferencer/error_local_unbound.py b/lit-test/test/inferencer/error_local_unbound.py
index 6b4350157..7327a8548 100644
--- a/lit-test/test/inferencer/error_local_unbound.py
+++ b/lit-test/test/inferencer/error_local_unbound.py
@@ -1,5 +1,5 @@
 # RUN: %python -m artiq.compiler.testbench.inferencer +diag %s >%t
 # RUN: OutputCheck %s --file-to-check=%t
 
-# CHECK-L: ${LINE:+1}: fatal: name 'x' is not bound to anything
+# CHECK-L: ${LINE:+1}: fatal: undefined variable 'x'
 x
diff --git a/lit-test/test/inferencer/exception.py b/lit-test/test/inferencer/exception.py
index bfdbbfb7c..e0e0f9645 100644
--- a/lit-test/test/inferencer/exception.py
+++ b/lit-test/test/inferencer/exception.py
@@ -1,7 +1,7 @@
 # RUN: %python -m artiq.compiler.testbench.inferencer %s >%t
 # RUN: OutputCheck %s --file-to-check=%t
 
-# CHECK-L: Exception:<constructor Exception>
+# CHECK-L: Exception:<constructor Exception {}>
 Exception
 
 try:
diff --git a/lit-test/test/inferencer/unify.py b/lit-test/test/inferencer/unify.py
index c6f41b495..31679beb6 100644
--- a/lit-test/test/inferencer/unify.py
+++ b/lit-test/test/inferencer/unify.py
@@ -58,16 +58,16 @@ k = "x"
 # CHECK-L: k:str
 
 IndexError()
-# CHECK-L: IndexError:<constructor IndexError>():IndexError
+# CHECK-L: IndexError:<constructor IndexError {}>():IndexError
 
 IndexError("x")
-# CHECK-L: IndexError:<constructor IndexError>("x":str):IndexError
+# CHECK-L: IndexError:<constructor IndexError {}>("x":str):IndexError
 
 IndexError("x", 1)
-# CHECK-L: IndexError:<constructor IndexError>("x":str, 1:int(width=64)):IndexError
+# CHECK-L: IndexError:<constructor IndexError {}>("x":str, 1:int(width=64)):IndexError
 
 IndexError("x", 1, 1)
-# CHECK-L: IndexError:<constructor IndexError>("x":str, 1:int(width=64), 1:int(width=64)):IndexError
+# CHECK-L: IndexError:<constructor IndexError {}>("x":str, 1:int(width=64), 1:int(width=64)):IndexError
 
 IndexError("x", 1, 1, 1)
-# CHECK-L: IndexError:<constructor IndexError>("x":str, 1:int(width=64), 1:int(width=64), 1:int(width=64)):IndexError
+# CHECK-L: IndexError:<constructor IndexError {}>("x":str, 1:int(width=64), 1:int(width=64), 1:int(width=64)):IndexError
diff --git a/lit-test/test/integration/class.py b/lit-test/test/integration/class.py
new file mode 100644
index 000000000..1937ec85f
--- /dev/null
+++ b/lit-test/test/integration/class.py
@@ -0,0 +1,12 @@
+# RUN: %python -m artiq.compiler.testbench.jit %s
+# RUN: %python %s
+
+class c:
+    a = 1
+    def f():
+        return 2
+
+# CHECK-L: a 1
+print("a", c.a)
+# CHECK-L: f() 2
+print("f()", c.f())