diff --git a/artiq/compiler/__init__.py b/artiq/compiler/__init__.py
index 8f210ac92..1d187a71b 100644
--- a/artiq/compiler/__init__.py
+++ b/artiq/compiler/__init__.py
@@ -1 +1 @@
-from .module import Module
+from .module import Module, Source
diff --git a/artiq/compiler/module.py b/artiq/compiler/module.py
index 133284e95..2f62da1d8 100644
--- a/artiq/compiler/module.py
+++ b/artiq/compiler/module.py
@@ -1,36 +1,62 @@
 """
-The :class:`Module` class encapsulates a single Python
+The :class:`Module` class encapsulates a single Python module,
+which corresponds to a single ARTIQ translation unit (one LLVM
+bitcode file and one object file, unless LTO is used).
+A :class:`Module` can be created from a typed AST.
+
+The :class:`Source` class parses a single source file or
+string and infers types for it using a trivial :module:`prelude`.
 """
 
 import os
 from pythonparser import source, diagnostic, parse_buffer
 from . import prelude, types, transforms, validators
 
-class Module:
+class Source:
     def __init__(self, source_buffer, engine=None):
         if engine is None:
-            engine = diagnostic.Engine(all_errors_are_fatal=True)
+            self.engine = diagnostic.Engine(all_errors_are_fatal=True)
+        else:
+            self.engine = engine
 
         self.name, _ = os.path.splitext(os.path.basename(source_buffer.name))
 
-        asttyped_rewriter = transforms.ASTTypedRewriter(engine=engine)
+        asttyped_rewriter = transforms.ASTTypedRewriter(engine=engine,
+                                                        globals=prelude.globals())
         inferencer = transforms.Inferencer(engine=engine)
-        int_monomorphizer = transforms.IntMonomorphizer(engine=engine)
-        monomorphism_validator = validators.MonomorphismValidator(engine=engine)
-        escape_validator = validators.EscapeValidator(engine=engine)
-        artiq_ir_generator = transforms.ARTIQIRGenerator(engine=engine, module_name=self.name)
-        dead_code_eliminator = transforms.DeadCodeEliminator(engine=engine)
-        local_access_validator = validators.LocalAccessValidator(engine=engine)
 
         self.parsetree, self.comments = parse_buffer(source_buffer, engine=engine)
         self.typedtree = asttyped_rewriter.visit(self.parsetree)
         self.globals = asttyped_rewriter.globals
         inferencer.visit(self.typedtree)
-        int_monomorphizer.visit(self.typedtree)
-        inferencer.visit(self.typedtree)
-        monomorphism_validator.visit(self.typedtree)
-        escape_validator.visit(self.typedtree)
-        self.artiq_ir = artiq_ir_generator.visit(self.typedtree)
+
+    @classmethod
+    def from_string(cls, source_string, name="input.py", first_line=1, engine=None):
+        return cls(source.Buffer(source_string + "\n", name, first_line), engine=engine)
+
+    @classmethod
+    def from_filename(cls, filename, engine=None):
+        with open(filename) as f:
+            return cls(source.Buffer(f.read(), filename, 1), engine=engine)
+
+class Module:
+    def __init__(self, src):
+        int_monomorphizer = transforms.IntMonomorphizer(engine=src.engine)
+        inferencer = transforms.Inferencer(engine=src.engine)
+        monomorphism_validator = validators.MonomorphismValidator(engine=src.engine)
+        escape_validator = validators.EscapeValidator(engine=src.engine)
+        artiq_ir_generator = transforms.ARTIQIRGenerator(engine=src.engine,
+                                                         module_name=src.name)
+        dead_code_eliminator = transforms.DeadCodeEliminator(engine=src.engine)
+        local_access_validator = validators.LocalAccessValidator(engine=src.engine)
+
+        self.name = src.name
+        self.globals = src.globals
+        int_monomorphizer.visit(src.typedtree)
+        inferencer.visit(src.typedtree)
+        monomorphism_validator.visit(src.typedtree)
+        escape_validator.visit(src.typedtree)
+        self.artiq_ir = artiq_ir_generator.visit(src.typedtree)
         dead_code_eliminator.process(self.artiq_ir)
         # local_access_validator.process(self.artiq_ir)
 
@@ -43,15 +69,6 @@ class Module:
         """Return the name of the function that is the entry point of this module."""
         return self.name + ".__modinit__"
 
-    @classmethod
-    def from_string(cls, source_string, name="input.py", first_line=1, engine=None):
-        return cls(source.Buffer(source_string + "\n", name, first_line), engine=engine)
-
-    @classmethod
-    def from_filename(cls, filename, engine=None):
-        with open(filename) as f:
-            return cls(source.Buffer(f.read(), filename, 1), engine=engine)
-
     def __repr__(self):
         printer = types.TypePrinter()
         globals = ["%s: %s" % (var, printer.name(self.globals[var])) for var in self.globals]
diff --git a/artiq/compiler/testbench/inferencer.py b/artiq/compiler/testbench/inferencer.py
index e6e73ea60..d11150c43 100644
--- a/artiq/compiler/testbench/inferencer.py
+++ b/artiq/compiler/testbench/inferencer.py
@@ -66,7 +66,7 @@ def main():
     buf = source.Buffer("".join(fileinput.input()).expandtabs(),
                         os.path.basename(fileinput.filename()))
     parsed, comments = parse_buffer(buf, engine=engine)
-    typed = ASTTypedRewriter(engine=engine).visit(parsed)
+    typed = ASTTypedRewriter(engine=engine, globals=prelude.globals()).visit(parsed)
     Inferencer(engine=engine).visit(typed)
     if monomorphize:
         IntMonomorphizer(engine=engine).visit(typed)
diff --git a/artiq/compiler/testbench/irgen.py b/artiq/compiler/testbench/irgen.py
index 20e9334ca..4add27c20 100644
--- a/artiq/compiler/testbench/irgen.py
+++ b/artiq/compiler/testbench/irgen.py
@@ -1,6 +1,6 @@
 import sys, fileinput
 from pythonparser import diagnostic
-from .. import Module
+from .. import Module, Source
 
 def main():
     def process_diagnostic(diag):
@@ -11,7 +11,7 @@ def main():
     engine = diagnostic.Engine()
     engine.process = process_diagnostic
 
-    mod = Module.from_string("".join(fileinput.input()).expandtabs(), engine=engine)
+    mod = Module(Source.from_string("".join(fileinput.input()).expandtabs(), engine=engine))
     for fn in mod.artiq_ir:
         print(fn)
 
diff --git a/artiq/compiler/testbench/jit.py b/artiq/compiler/testbench/jit.py
index 4e99504c1..717bdc555 100644
--- a/artiq/compiler/testbench/jit.py
+++ b/artiq/compiler/testbench/jit.py
@@ -1,7 +1,7 @@
 import os, sys, fileinput, ctypes
 from pythonparser import diagnostic
 from llvmlite_artiq import binding as llvm
-from .. import Module
+from .. import Module, Source
 from ..targets import NativeTarget
 
 def main():
@@ -19,7 +19,7 @@ def main():
 
     source = "".join(fileinput.input())
     source = source.replace("#ARTIQ#", "")
-    mod = Module.from_string(source.expandtabs(), engine=engine)
+    mod = Module(Source.from_string(source.expandtabs(), engine=engine))
 
     target = NativeTarget()
     llmod = mod.build_llvm_ir(target)
diff --git a/artiq/compiler/testbench/llvmgen.py b/artiq/compiler/testbench/llvmgen.py
index 3f72569ac..33500ec8b 100644
--- a/artiq/compiler/testbench/llvmgen.py
+++ b/artiq/compiler/testbench/llvmgen.py
@@ -1,7 +1,7 @@
 import sys, fileinput
 from pythonparser import diagnostic
 from llvmlite_artiq import ir as ll
-from .. import Module
+from .. import Module, Source
 from ..targets import NativeTarget
 
 def main():
@@ -13,7 +13,7 @@ def main():
     engine = diagnostic.Engine()
     engine.process = process_diagnostic
 
-    mod = Module.from_string("".join(fileinput.input()).expandtabs(), engine=engine)
+    mod = Module(Source.from_string("".join(fileinput.input()).expandtabs(), engine=engine))
 
     target = NativeTarget()
     llmod = mod.build_llvm_ir(target=target)
diff --git a/artiq/compiler/testbench/perf.py b/artiq/compiler/testbench/perf.py
index c24946fb6..a5b3bdcc0 100644
--- a/artiq/compiler/testbench/perf.py
+++ b/artiq/compiler/testbench/perf.py
@@ -1,6 +1,6 @@
 import sys, os, time, cProfile as profile, pstats
 from pythonparser import diagnostic
-from .. import Module
+from .. import Module, Source
 from ..targets import OR1KTarget
 
 def main():
@@ -17,7 +17,7 @@ def main():
     engine.process = process_diagnostic
 
     # Make sure everything's valid
-    modules = [Module.from_filename(filename, engine=engine)
+    modules = [Module(Source.from_filename(filename, engine=engine))
                for filename in sys.argv[1:]]
 
     def benchmark(f, name):
diff --git a/artiq/compiler/testbench/shlib.py b/artiq/compiler/testbench/shlib.py
index c3236129a..97c19f11b 100644
--- a/artiq/compiler/testbench/shlib.py
+++ b/artiq/compiler/testbench/shlib.py
@@ -1,6 +1,6 @@
 import sys, os
 from pythonparser import diagnostic
-from .. import Module
+from .. import Module, Source
 from ..targets import OR1KTarget
 
 def main():
@@ -18,7 +18,7 @@ def main():
 
     modules = []
     for filename in sys.argv[1:]:
-        modules.append(Module.from_filename(filename, engine=engine))
+        modules.append(Module(Source.from_filename(filename, engine=engine)))
 
     llobj = OR1KTarget().compile_and_link(modules)
 
diff --git a/artiq/compiler/testbench/signature.py b/artiq/compiler/testbench/signature.py
index 1882260bf..774259540 100644
--- a/artiq/compiler/testbench/signature.py
+++ b/artiq/compiler/testbench/signature.py
@@ -1,6 +1,6 @@
 import sys, fileinput
 from pythonparser import diagnostic
-from .. import Module
+from .. import Module, Source
 
 def main():
     if len(sys.argv) > 1 and sys.argv[1] == "+diag":
@@ -21,7 +21,7 @@ def main():
     engine.process = process_diagnostic
 
     try:
-        mod = Module.from_string("".join(fileinput.input()).expandtabs(), engine=engine)
+        mod = Module(Source.from_string("".join(fileinput.input()).expandtabs(), engine=engine))
         print(repr(mod))
     except:
         if not diag: raise
diff --git a/artiq/compiler/transforms/asttyped_rewriter.py b/artiq/compiler/transforms/asttyped_rewriter.py
index 307033d1d..cc0de6b2c 100644
--- a/artiq/compiler/transforms/asttyped_rewriter.py
+++ b/artiq/compiler/transforms/asttyped_rewriter.py
@@ -4,7 +4,7 @@ to a typedtree (:mod:`..asttyped`).
 """
 
 from pythonparser import algorithm, diagnostic
-from .. import asttyped, types, builtins, prelude
+from .. import asttyped, types, builtins
 
 # This visitor will be called for every node with a scope,
 # i.e.: class, function, comprehension, lambda
@@ -185,10 +185,10 @@ class ASTTypedRewriter(algorithm.Transformer):
     via :class:`LocalExtractor`.
     """
 
-    def __init__(self, engine):
+    def __init__(self, engine, globals):
         self.engine = engine
         self.globals = None
-        self.env_stack = [prelude.globals()]
+        self.env_stack = [globals]
 
     def _find_name(self, name, loc):
         for typing_env in reversed(self.env_stack):