Fix "Internal error ... local variable 'errstr' referenced before assignment during BoundFunction(...)"

numba/core/types/functions.py

@@ -401,8 +401,8 @@ def add_bt(error):
                     else:
                         bt = [""]
                     nd2indent = '\n{}'.format(2 * indent)
-                    errstr += _termcolor.reset(nd2indent +
-                                               nd2indent.join(bt_as_lines))
+                    errstr = _termcolor.reset(nd2indent +
+                                               nd2indent.join(_bt_as_lines(bt)))
                     return _termcolor.reset(errstr)
             else:
                 add_bt = lambda X: ''

numba/tests/test_errorhandling.py

@@ -18,7 +18,8 @@
 from numba.core.compiler_machinery import PassManager
 from numba.core.types.functions import _err_reasons as error_reasons
 
-from numba.tests.support import skip_parfors_unsupported
+from numba.tests.support import (skip_parfors_unsupported, override_config,
+                                 SerialMixin)
 import unittest
 
 # used in TestMiscErrorHandling::test_handling_of_write_to_*_global
@@ -423,5 +424,22 @@ def foo():
         self.assertIn("Type Restricted Function in function 'unknown'", excstr)
 
 
+class TestDeveloperSpecificErrorMessages(SerialMixin, unittest.TestCase):
+
+    def test_bound_function_error_string(self):
+        # See PR #5952
+        def foo(x):
+            x.max(-1) # axis not supported
+
+        with override_config('DEVELOPER_MODE', 1):
+            with self.assertRaises(errors.TypingError) as raises:
+                njit("void(int64[:,:])")(foo)
+
+        excstr = str(raises.exception)
+        self.assertIn("AssertionError()", excstr)
+        self.assertIn("BoundFunction(array.max for array(int64, 2d, A))",
+                      excstr)
+
+
 if __name__ == '__main__':
     unittest.main()