From 09a570e1efe6fb45c01fc8dc96d64a799ab879ee Mon Sep 17 00:00:00 2001
From: Siu Kwan Lam <michael.lam.sk@gmail.com>
Date: Wed, 6 May 2020 10:22:06 -0500
Subject: [PATCH 1/2] Restore numba.types as public API

---
 numba/tests/test_moved_modules.py | 21 +++++++++++++++++++++
 numba/types/__init__.py           |  3 +++
 2 files changed, 24 insertions(+)
 create mode 100644 numba/tests/test_moved_modules.py
 create mode 100644 numba/types/__init__.py

diff --git a/numba/tests/test_moved_modules.py b/numba/tests/test_moved_modules.py
new file mode 100644
index 00000000000..81e61a2f108
--- /dev/null
+++ b/numba/tests/test_moved_modules.py
@@ -0,0 +1,21 @@
+"""Tests for moved modules and their redirection from old path
+"""
+from numba.tests.support import TestCase
+
+
+class TestMovedModule(TestCase):
+    """Testing moved modules in Q1 2020 but were decided to kept as public API
+    """
+    def tests_numba_types(self):
+        import numba.types
+        import numba.core.types as types
+        # The old module is the new module
+        self.assertIs(numba.types, types)
+        # Attribute access are there
+        self.assertIs(numba.types.intp, types.intp)
+        self.assertIs(numba.types.float64, types.float64)
+        self.assertIs(numba.types.Array, types.Array)
+        # Submodule access through old import path is possible
+        import numba.types.misc
+        self.assertIs(types.misc, numba.types.misc)
+        self.assertIs(types.misc.Optional, numba.types.misc.Optional)
diff --git a/numba/types/__init__.py b/numba/types/__init__.py
new file mode 100644
index 00000000000..cab9204c75c
--- /dev/null
+++ b/numba/types/__init__.py
@@ -0,0 +1,3 @@
+import sys
+import numba.core.types
+sys.modules[__name__] = numba.core.types

From 2998661e6f33d8b437aadd70f0b0f08302524b0e Mon Sep 17 00:00:00 2001
From: Siu Kwan Lam <michael.lam.sk@gmail.com>
Date: Wed, 6 May 2020 12:05:44 -0500
Subject: [PATCH 2/2] A better subpackage redirection

---
 numba/core/utils.py               | 36 +++++++++++++++++++++++++++++++
 numba/tests/test_moved_modules.py | 13 +++++++++--
 numba/types/__init__.py           |  5 +++--
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/numba/core/utils.py b/numba/core/utils.py
index b5703de5e19..9909f85ae4e 100644
--- a/numba/core/utils.py
+++ b/numba/core/utils.py
@@ -12,6 +12,7 @@
 import weakref
 import warnings
 from types import ModuleType
+from importlib import import_module
 from collections.abc import Mapping
 import numpy as np
 
@@ -555,3 +556,38 @@ def unified_function_type(numba_types, require_precise=True):
         function = types.UndefinedFunctionType(mnargs, dispatchers)
 
     return function
+
+
+class _RedirectSubpackage(ModuleType):
+    """Redirect a subpackage to a subpackage.
+
+    This allows all references like:
+
+    >>> from numba.old_subpackage import module
+    >>> module.item
+
+    >>> import numba.old_subpackage.module
+    >>> numba.old_subpackage.module.item
+
+    >>> from numba.old_subpackage.module import item
+    """
+    def __init__(self, old_module_locals, new_module):
+        old_module = old_module_locals['__name__']
+        super().__init__(old_module)
+
+        new_mod_obj = import_module(new_module)
+
+        # Map all sub-modules over
+        for k, v in new_mod_obj.__dict__.items():
+            # Get attributes so that `subpackage.xyz` and
+            # `from subpackage import xyz` work
+            setattr(self, k, v)
+            if isinstance(v, ModuleType):
+                # Map modules into the interpreter so that
+                # `import subpackage.xyz` works
+                sys.modules[f"{old_module}.{k}"] = sys.modules[v.__name__]
+
+        # copy across dunders so that package imports work too
+        for attr, value in old_module_locals.items():
+            if attr.startswith('__') and attr.endswith('__'):
+                setattr(self, attr, value)
diff --git a/numba/tests/test_moved_modules.py b/numba/tests/test_moved_modules.py
index 81e61a2f108..4ccaa06c9a4 100644
--- a/numba/tests/test_moved_modules.py
+++ b/numba/tests/test_moved_modules.py
@@ -9,8 +9,8 @@ class TestMovedModule(TestCase):
     def tests_numba_types(self):
         import numba.types
         import numba.core.types as types
-        # The old module is the new module
-        self.assertIs(numba.types, types)
+        # The old module IS NOT the new module
+        self.assertIsNot(numba.types, types)
         # Attribute access are there
         self.assertIs(numba.types.intp, types.intp)
         self.assertIs(numba.types.float64, types.float64)
@@ -19,3 +19,12 @@ def tests_numba_types(self):
         import numba.types.misc
         self.assertIs(types.misc, numba.types.misc)
         self.assertIs(types.misc.Optional, numba.types.misc.Optional)
+        # Import time code could be executed twice and causes the following to
+        # fail.
+        self.assertIs(types.StringLiteral, numba.types.misc.StringLiteral)
+        # Check numba.types.container
+        from numba.types import containers
+        self.assertIs(types.containers, containers)
+        self.assertIs(types.containers.Sequence, containers.Sequence)
+        from numba.types.containers import Sequence
+        self.assertIs(Sequence, containers.Sequence)
diff --git a/numba/types/__init__.py b/numba/types/__init__.py
index cab9204c75c..3bb9f219803 100644
--- a/numba/types/__init__.py
+++ b/numba/types/__init__.py
@@ -1,3 +1,4 @@
 import sys
-import numba.core.types
-sys.modules[__name__] = numba.core.types
+from numba.core.utils import _RedirectSubpackage
+sys.modules[__name__] = _RedirectSubpackage(locals(), "numba.core.types")
+