# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1693941409 -7200
# Node ID 582d834d392df5dfa7e48401e82d14d6549a9a01
# Parent  f646afbcfe1c7a74a8f75210c2984346dae223d1# Parent  06335a0e411366319ffbf4115086b8161d0cc28b
Merged changes from the value-replacement branch.

diff -r f646afbcfe1c -r 582d834d392d access_plan.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/access_plan.py	Tue Sep 05 21:16:49 2023 +0200
@@ -0,0 +1,545 @@
+#!/usr/bin/env python
+
+"""
+Attribute access plan translation.
+
+Copyright (C) 2014-2018, 2023 Paul Boddie <paul@boddie.org.uk>
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+details.
+
+You should have received a copy of the GNU General Public License along with
+this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+
+from encoders import encode_access_location
+
+class AccessPlan:
+
+    "An attribute access plan."
+
+    def __init__(self, name, test, test_type, base, traversed, traversal_modes,
+                 remaining, context, context_test, first_method, final_method,
+                 origin, accessor_kinds):
+
+        "Initialise the plan."
+
+        # With instance attribute initialisers, the assignment below would be
+        # generated automatically.
+
+        (
+            self.name, self.test, self.test_type, self.base,
+            self.traversed, self.traversal_modes, self.remaining,
+            self.context, self.context_test,
+            self.first_method, self.final_method,
+            self.origin, self.accessor_kinds) = (
+
+            name, test, test_type, base,
+            traversed, traversal_modes, remaining,
+            context, context_test,
+            first_method, final_method,
+            origin, accessor_kinds)
+
+        # Define the first attribute access and subsequent accesses.
+
+        self.first_attrname = None
+        self.traversed_attrnames = traversed
+        self.traversed_attrname_modes = traversal_modes
+        self.remaining_attrnames = remaining
+
+        if traversed:
+            self.first_attrname = traversed[0]
+            self.traversed_attrnames = traversed[1:]
+            self.traversed_attrname_modes = traversal_modes[1:]
+        elif remaining:
+            self.first_attrname = remaining[0]
+            self.remaining_attrnames = remaining[1:]
+
+    def access_first_attribute(self):
+
+        "Return whether the first attribute is to be accessed."
+
+        return self.final_method in ("access", "access-invoke", "assign") or \
+            self.all_subsequent_attributes()
+
+    def assigning_first_attribute(self):
+
+        "Return whether the first attribute access involves assignment."
+
+        return not self.all_subsequent_attributes() and self.final_method == "assign"
+
+    def get_first_attribute_name(self):
+
+        "Return any first attribute name to be used in an initial access."
+
+        return self.first_attrname
+
+    def all_subsequent_attributes(self):
+
+        "Return all subsequent attribute names involved in accesses."
+
+        return self.traversed_attrnames + self.remaining_attrnames
+
+    def attribute_traversals(self):
+
+        "Return a collection of (attribute name, traversal mode) tuples."
+
+        return zip(self.traversed_attrnames, self.traversed_attrname_modes)
+
+    def stored_accessor(self):
+
+        "Return the variable used to obtain the accessor."
+
+        return self.assigning_first_attribute() and "<target_accessor>" or "<accessor>"
+
+    def stored_accessor_modifier(self):
+
+        "Return the variable used to set the accessor."
+
+        return self.assigning_first_attribute() and "<set_target_accessor>" or "<set_accessor>"
+
+    def get_original_accessor(self):
+
+        "Return the original accessor details."
+
+        # Identify any static original accessor.
+
+        if self.base:
+            return self.base
+
+        # Employ names as contexts unless the context needs testing and
+        # potentially updating. In such cases, temporary context storage is
+        # used instead.
+
+        elif self.name and not (self.context_test == "test" and
+            self.final_method in ("access-invoke", "static-invoke")):
+
+            return "<name>"
+
+        # Use a generic placeholder representing the access expression in
+        # the general case.
+
+        else:
+            return "<expr>"
+
+    def get_instructions(self):
+
+        "Return a list of instructions corresponding to the plan."
+
+        # Emit instructions by appending them to a list.
+
+        instructions = []
+        emit = instructions.append
+
+        # Set up any initial instructions.
+
+        accessor, context = self.process_initialisation(emit)
+
+        # Apply any test.
+
+        if self.test[0] == "test":
+            test_accessor = accessor = ("__%s_%s_%s" % self.test, accessor, self.test_type)
+        else:
+            test_accessor = None
+
+        # Perform the first or final access.
+        # The access only needs performing if the resulting accessor is used.
+
+        accessor = self.process_first_attribute(accessor, emit)
+
+        # Perform accesses for the traversed and remaining attributes.
+
+        accessor, context = self.process_traversed_attributes(accessor, context, emit)
+        accessor, context = self.process_remaining_attributes(accessor, context, emit)
+
+        # Make any accessor test available if not emitted.
+
+        test_accessor = not instructions and test_accessor or None
+
+        # Perform the access on the actual target.
+
+        accessor, context = self.process_attribute_access(accessor, context, test_accessor, emit)
+
+        # Produce an advisory instruction regarding the context.
+
+        self.process_context_identity(context, emit)
+
+        # Produce an advisory instruction regarding the final attribute.
+
+        if self.origin:
+            emit(("<final_identity>", self.origin))
+
+        return instructions
+
+    def process_initialisation(self, emit):
+
+        """
+        Use 'emit' to generate instructions for any initialisation of attribute
+        access. Return the potentially revised accessor and context indicators.
+        """
+
+        # Identify any static original accessor.
+
+        original_accessor = self.get_original_accessor()
+
+        # Determine whether the first access involves assignment.
+
+        set_accessor = self.stored_accessor_modifier()
+        stored_accessor = self.stored_accessor()
+
+        # Set the context if already available.
+
+        context = None
+
+        if self.context == "base":
+            accessor = context = (self.base,)
+        elif self.context == "original-accessor":
+
+            # Prevent re-evaluation of any dynamic expression by storing it.
+
+            if original_accessor == "<expr>":
+                if self.final_method in ("access-invoke", "static-invoke"):
+                    emit(("<set_context>", original_accessor))
+                    accessor = context = ("<context>",)
+                else:
+                    emit((set_accessor, original_accessor))
+                    accessor = context = (stored_accessor,)
+            else:
+                accessor = context = (original_accessor,)
+
+        # Assigning does not set the context.
+
+        elif self.context in ("final-accessor", "unset") and self.access_first_attribute():
+
+            # Prevent re-evaluation of any dynamic expression by storing it.
+
+            if original_accessor == "<expr>":
+                emit((set_accessor, original_accessor))
+                accessor = (stored_accessor,)
+            else:
+                accessor = (original_accessor,)
+        else:
+            accessor = None
+
+        return accessor, context
+
+    def process_first_attribute(self, accessor, emit):
+
+        """
+        Using 'accessor', use 'emit' to generate instructions for any first
+        attribute access. Return the potentially revised accessor.
+        """
+
+        if self.access_first_attribute():
+            attrname = self.get_first_attribute_name()
+            assigning = self.assigning_first_attribute()
+
+            store = attrname != "__data__" and "__store_via_attr_ref" or "__store_via_attr_ref__"
+
+            # Access via the accessor's class.
+
+            if self.first_method == "relative-class":
+                if assigning:
+                    emit(("<set_attr_ref>", ("__get_class_attr_ref", accessor, attrname)))
+                    emit((store, "<attr_ref>", "<assexpr>"))
+                else:
+                    accessor = ("__load_via_class", accessor, attrname)
+
+            # Access via the accessor itself.
+
+            elif self.first_method == "relative-object":
+                if assigning:
+                    emit(("<set_attr_ref>", ("__get_object_attr_ref", accessor, attrname)))
+                    emit((store, "<attr_ref>", "<assexpr>"))
+                else:
+                    accessor = ("__load_via_object", accessor, attrname)
+
+            # Access via a class accessor or the accessor's class.
+
+            elif self.first_method == "relative-object-class":
+                if assigning:
+                    emit(("__raise_type_error",))
+                else:
+                    accessor = ("__get_class_and_load", accessor, attrname)
+
+            # Access via the accessor's class.
+
+            elif self.first_method == "check-class":
+                if assigning:
+                    emit(("__raise_type_error",))
+                else:
+                    accessor = ("__check_and_load_via_class", accessor, attrname)
+
+            # Access via the accessor itself.
+
+            elif self.first_method == "check-object":
+                if assigning:
+                    emit(("<set_attr_ref>", ("__check_and_get_object_attr_ref", accessor, attrname)))
+                    emit((store, "<attr_ref>", "<assexpr>"))
+                else:
+                    accessor = ("__check_and_load_via_object", accessor, attrname)
+
+            # Access via a class accessor or the accessor's class.
+            # Here, only access via the accessor is supported.
+
+            elif self.first_method == "check-object-class":
+                if assigning:
+                    emit(("<set_attr_ref>", ("__check_and_get_object_attr_ref", accessor, attrname)))
+                    emit((store, "<attr_ref>", "<assexpr>"))
+                else:
+                    accessor = ("__check_and_load_via_any", accessor, attrname)
+
+        return accessor
+
+    def process_traversed_attributes(self, accessor, context, emit):
+
+        """
+        Using 'accessor' and 'context', use 'emit' to generate instructions
+        for the traversed attribute accesses. Return the potentially revised
+        accessor and context indicators.
+        """
+
+        # Traverse attributes using the accessor.
+
+        num_remaining = len(self.all_subsequent_attributes())
+
+        if self.traversed_attrnames:
+            for attrname, traversal_mode in self.attribute_traversals():
+                assigning = num_remaining == 1 and self.final_method == "assign"
+
+                # Set the context, if appropriate.
+
+                if num_remaining == 1 and self.final_method != "assign" and self.context == "final-accessor":
+
+                    # Invoked attributes employ a separate context accessed
+                    # during invocation.
+
+                    if self.final_method in ("access-invoke", "static-invoke"):
+                        emit(("<set_context>", accessor))
+                        accessor = context = "<context>"
+
+                    # A private context within the access is otherwise
+                    # retained.
+
+                    else:
+                        emit(("<set_private_context>", accessor))
+                        accessor = context = "<private_context>"
+
+                # Perform the access only if not achieved directly.
+
+                if num_remaining > 1 or self.final_method in ("access", "access-invoke", "assign"):
+
+                    store = attrname != "__data__" and "__store_via_attr_ref" or "__store_via_attr_ref__"
+
+                    if traversal_mode == "class":
+                        if assigning:
+                            emit(("<set_attr_ref>", ("__get_class_attr_ref", accessor, attrname)))
+                            emit((store, "<attr_ref>", "<assexpr>"))
+                        else:
+                            accessor = ("__load_via_class", accessor, attrname)
+                    else:
+                        if assigning:
+                            emit(("<set_attr_ref>", ("__get_object_attr_ref", accessor, attrname)))
+                            emit((store, "<attr_ref>", "<assexpr>"))
+                        else:
+                            accessor = ("__load_via_object", accessor, attrname)
+
+                num_remaining -= 1
+
+        return accessor, context
+
+    def process_remaining_attributes(self, accessor, context, emit):
+
+        """
+        Using 'accessor' and 'context', use 'emit' to generate instructions
+        for the remaining attribute accesses. Return the potentially revised
+        accessor and context indicators.
+        """
+
+        remaining = self.remaining_attrnames
+
+        if remaining:
+            num_remaining = len(remaining)
+
+            for attrname in remaining:
+                assigning = num_remaining == 1 and self.final_method == "assign"
+
+                # Set the context, if appropriate.
+
+                if num_remaining == 1 and self.final_method != "assign" and self.context == "final-accessor":
+
+                    # Invoked attributes employ a separate context accessed
+                    # during invocation.
+
+                    if self.final_method in ("access-invoke", "static-invoke"):
+                        emit(("<set_context>", accessor))
+                        accessor = context = "<context>"
+
+                    # A private context within the access is otherwise
+                    # retained.
+
+                    else:
+                        emit(("<set_private_context>", accessor))
+                        accessor = context = "<private_context>"
+
+                # Perform the access only if not achieved directly.
+
+                if num_remaining > 1 or self.final_method in ("access", "access-invoke", "assign"):
+
+                    # Constrain instructions involving certain special
+                    # attribute names.
+
+                    store = attrname != "__data__" and "__store_via_attr_ref" or "__store_via_attr_ref__"
+                    to_search = attrname != "__data__" and "any" or "object"
+
+                    if assigning:
+                        emit(("<set_attr_ref>", ("__check_and_get_object_attr_ref", accessor, attrname)))
+                        emit((store, "<attr_ref>", "<assexpr>"))
+                    else:
+                        accessor = ("__check_and_load_via_%s" % to_search, accessor, attrname)
+
+                num_remaining -= 1
+
+        return accessor, context
+
+    def process_attribute_access(self, accessor, context, test_accessor, emit):
+
+        """
+        Using 'accessor','context' and any 'test_accessor' operation, use 'emit'
+        to generate instructions for the final attribute access. Return the
+        potentially revised accessor and context indicators.
+        """
+
+        # Define any replacement context variable plus the default eventual
+        # context variable.
+
+        replacement_context = "<new_context>"
+        final_context = context
+
+        # Define or emit the means of accessing the actual target.
+
+        if self.final_method in ("static", "static-assign", "static-invoke"):
+
+            if test_accessor:
+                emit(test_accessor)
+
+            # Assignments to known attributes.
+
+            if self.final_method == "static-assign":
+                parent, attrname = self.origin.rsplit(".", 1)
+                store = attrname != "__data__" and "__store_via_attr_ref" or "__store_via_attr_ref__"
+                emit(("<set_attr_ref>", ("__get_object_attr_ref", parent, attrname)))
+                emit((store, "<attr_ref>", "<assexpr>"))
+
+            # Invoked attributes employ a separate context.
+
+            elif self.final_method in ("static", "static-invoke"):
+                accessor = ("__load_static_ignore", self.origin)
+
+        # Wrap accesses in context operations.
+
+        if self.context_test == "test":
+
+            # Test and combine the context with static attribute details.
+
+            if self.final_method == "static":
+                emit(("__load_static_test", replacement_context, context, self.origin))
+                final_context = replacement_context
+
+            # Test the context, storing it separately if required for the
+            # immediately invoked static attribute.
+
+            elif self.final_method == "static-invoke":
+                emit(("<test_context_static>", context, self.origin))
+
+            # Test the context, storing it separately if required for an
+            # immediately invoked attribute.
+
+            elif self.final_method == "access-invoke":
+                emit(("<test_context_revert>", context, accessor))
+
+            # Test the context and update the attribute details if
+            # appropriate.
+
+            else:
+                emit(("__test_context", replacement_context, context, accessor))
+                final_context = replacement_context
+
+        elif self.context_test == "replace":
+
+            # Produce an object with updated context.
+
+            if self.final_method == "static":
+                emit(("__load_static_replace", replacement_context, context, self.origin))
+                final_context = replacement_context
+
+            # Omit the context update operation where the target is static
+            # and the context is recorded separately.
+
+            elif self.final_method == "static-invoke":
+                pass
+
+            # If a separate context is used for an immediate invocation,
+            # produce the attribute details unchanged.
+
+            elif self.final_method == "access-invoke":
+                emit(accessor)
+
+            # Update the context in the attribute details.
+
+            else:
+                emit(("__update_context", replacement_context, context, accessor))
+                final_context = replacement_context
+
+        # Omit the accessor for assignments and for invocations of static
+        # targets. Otherwise, emit the accessor which may involve the
+        # invocation of a test.
+
+        elif self.final_method not in ("assign", "static-assign", "static-invoke"):
+            emit(accessor)
+
+        return accessor, final_context
+
+    def process_context_identity(self, context, emit):
+
+        """
+        Using 'context', use 'emit' to generate instructions to test the context
+        identity.
+        """
+
+        if context:
+
+            # Only verify the context for invocation purposes if a suitable
+            # test has been performed.
+
+            if self.context_test in ("ignore", "replace") or \
+               self.final_method in ("access-invoke", "static-invoke"):
+
+                emit(("<context_identity_verified>", context))
+            else:
+                emit(("<context_identity>", context))
+
+    def write(self, f, location):
+
+        "Write the plan to file 'f' with the given 'location' information."
+
+        print >>f, encode_access_location(location), \
+                   self.name or "{}", \
+                   self.test and "-".join(self.test) or "{}", \
+                   self.test_type or "{}", \
+                   self.base or "{}", \
+                   ".".join(self.traversed_attrnames) or "{}", \
+                   ".".join(self.traversed_attrname_modes) or "{}", \
+                   ".".join(self.remaining_attrnames) or "{}", \
+                   self.context, self.context_test, \
+                   self.first_method, self.final_method, self.origin or "{}", \
+                   ",".join(self.accessor_kinds)
+
+# vim: tabstop=4 expandtab shiftwidth=4
diff -r f646afbcfe1c -r 582d834d392d deducer.py
--- a/deducer.py	Sun Sep 03 00:24:29 2023 +0200
+++ b/deducer.py	Tue Sep 05 21:16:49 2023 +0200
@@ -19,6 +19,7 @@
 this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
+from access_plan import AccessPlan
 from common import first, get_assigned_attributes, get_attrnames, \
                    get_invoked_attributes, get_name_path, init_item, \
                    order_dependencies_partial, sorted_output, \
@@ -477,23 +478,7 @@
             locations.sort()
 
             for location in locations:
-                name, test, test_type, base, \
-                    traversed, traversal_modes, attrnames, \
-                    context, context_test, \
-                    first_method, final_method, \
-                    attr, accessor_kinds = self.access_plans[location]
-
-                print >>f_attrs, encode_access_location(location), \
-                                 name or "{}", \
-                                 test and "-".join(test) or "{}", \
-                                 test_type or "{}", \
-                                 base or "{}", \
-                                 ".".join(traversed) or "{}", \
-                                 ".".join(traversal_modes) or "{}", \
-                                 ".".join(attrnames) or "{}", \
-                                 context, context_test, \
-                                 first_method, final_method, attr or "{}", \
-                                 ",".join(accessor_kinds)
+                self.access_plans[location].write(f_attrs, location)
 
         finally:
             f_attrs.close()
@@ -2637,364 +2622,18 @@
                       (base and "base" or "original-accessor") or \
                   "final-accessor"
 
-        return name, test, test_type, base, \
-               traversed, traversal_modes, remaining, \
-               context, context_test, \
-               first_method, final_method, \
-               origin, accessor_kinds
+        return AccessPlan(name, test, test_type, base,
+                          traversed, traversal_modes, remaining,
+                          context, context_test,
+                          first_method, final_method,
+                          origin, accessor_kinds)
 
     def initialise_access_instructions(self):
 
         "Expand access plans into instruction sequences."
 
         for access_location, access_plan in self.access_plans.items():
-
-            # Obtain the access details.
-
-            name, test, test_type, base, \
-                traversed, traversal_modes, attrnames, \
-                context, context_test, \
-                first_method, final_method, \
-                origin, accessor_kinds = access_plan
-
-            # Emit instructions by appending them to a list.
-
-            instructions = []
-            emit = instructions.append
-
-            # Identify any static original accessor.
-
-            if base:
-                original_accessor = base
-
-            # Employ names as contexts unless the context needs testing and
-            # potentially updating. In such cases, temporary context storage is
-            # used instead.
-
-            elif name and not (context_test == "test" and
-                               final_method in ("access-invoke", "static-invoke")):
-                original_accessor = "<name>" # refers to the name
-
-            # Use a generic placeholder representing the access expression in
-            # the general case.
-
-            else:
-                original_accessor = "<expr>"
-
-            # Prepare for any first attribute access.
-
-            if traversed:
-                attrname = traversed[0]
-                del traversed[0]
-            elif attrnames:
-                attrname = attrnames[0]
-                del attrnames[0]
-
-            # Perform the first access explicitly if at least one operation
-            # requires it.
-
-            access_first_attribute = final_method in ("access", "access-invoke", "assign") or traversed or attrnames
-
-            # Determine whether the first access involves assignment.
-
-            assigning = not traversed and not attrnames and final_method == "assign"
-            set_accessor = assigning and "<set_target_accessor>" or "<set_accessor>"
-            stored_accessor = assigning and "<target_accessor>" or "<accessor>"
-
-            # Set the context if already available.
-
-            context_var = None
-
-            if context == "base":
-                accessor = context_var = (base,)
-            elif context == "original-accessor":
-
-                # Prevent re-evaluation of any dynamic expression by storing it.
-
-                if original_accessor == "<expr>":
-                    if final_method in ("access-invoke", "static-invoke"):
-                        emit(("<set_context>", original_accessor))
-                        accessor = context_var = ("<context>",)
-                    else:
-                        emit((set_accessor, original_accessor))
-                        accessor = context_var = (stored_accessor,)
-                else:
-                    accessor = context_var = (original_accessor,)
-
-            # Assigning does not set the context.
-
-            elif context in ("final-accessor", "unset") and access_first_attribute:
-
-                # Prevent re-evaluation of any dynamic expression by storing it.
-
-                if original_accessor == "<expr>":
-                    emit((set_accessor, original_accessor))
-                    accessor = (stored_accessor,)
-                else:
-                    accessor = (original_accessor,)
-            else:
-                accessor = None
-
-            # Apply any test.
-
-            if test[0] == "test":
-                test_accessor = accessor = ("__%s_%s_%s" % test, accessor, test_type)
-            else:
-                test_accessor = None
-
-            # Perform the first or final access.
-            # The access only needs performing if the resulting accessor is used.
-
-            remaining = len(traversed + attrnames)
-
-            if access_first_attribute:
-
-                # Access via the accessor's class.
-
-                if first_method == "relative-class":
-                    if assigning:
-                        emit(("<set_attr_ref>", ("__get_class_attr_ref", accessor, attrname)))
-                        emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                    else:
-                        accessor = ("__load_via_class", accessor, attrname)
-
-                # Access via the accessor itself.
-
-                elif first_method == "relative-object":
-                    if assigning:
-                        emit(("<set_attr_ref>", ("__get_object_attr_ref", accessor, attrname)))
-                        emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                    else:
-                        accessor = ("__load_via_object", accessor, attrname)
-
-                # Access via a class accessor or the accessor's class.
-
-                elif first_method == "relative-object-class":
-                    if assigning:
-                        emit(("__raise_type_error",))
-                    else:
-                        accessor = ("__get_class_and_load", accessor, attrname)
-
-                # Access via the accessor's class.
-
-                elif first_method == "check-class":
-                    if assigning:
-                        emit(("__raise_type_error",))
-                    else:
-                        accessor = ("__check_and_load_via_class", accessor, attrname)
-
-                # Access via the accessor itself.
-
-                elif first_method == "check-object":
-                    if assigning:
-                        emit(("<set_attr_ref>", ("__check_and_get_object_attr_ref", accessor, attrname)))
-                        emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                    else:
-                        accessor = ("__check_and_load_via_object", accessor, attrname)
-
-                # Access via a class accessor or the accessor's class.
-                # Here, only access via the accessor is supported.
-
-                elif first_method == "check-object-class":
-                    if assigning:
-                        emit(("<set_attr_ref>", ("__check_and_get_object_attr_ref", accessor, attrname)))
-                        emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                    else:
-                        accessor = ("__check_and_load_via_any", accessor, attrname)
-
-            # Traverse attributes using the accessor.
-
-            if traversed:
-                for attrname, traversal_mode in zip(traversed, traversal_modes):
-                    assigning = remaining == 1 and final_method == "assign"
-
-                    # Set the context, if appropriate.
-
-                    if remaining == 1 and final_method != "assign" and context == "final-accessor":
-
-                        # Invoked attributes employ a separate context accessed
-                        # during invocation.
-
-                        if final_method in ("access-invoke", "static-invoke"):
-                            emit(("<set_context>", accessor))
-                            accessor = context_var = "<context>"
-
-                        # A private context within the access is otherwise
-                        # retained.
-
-                        else:
-                            emit(("<set_private_context>", accessor))
-                            accessor = context_var = "<private_context>"
-
-                    # Perform the access only if not achieved directly.
-
-                    if remaining > 1 or final_method in ("access", "access-invoke", "assign"):
-
-                        if traversal_mode == "class":
-                            if assigning:
-                                emit(("<set_attr_ref>", ("__get_class_attr_ref", accessor, attrname)))
-                                emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                            else:
-                                accessor = ("__load_via_class", accessor, attrname)
-                        else:
-                            if assigning:
-                                emit(("<set_attr_ref>", ("__get_object_attr_ref", accessor, attrname)))
-                                emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                            else:
-                                accessor = ("__load_via_object", accessor, attrname)
-
-                    remaining -= 1
-
-            if attrnames:
-                for attrname in attrnames:
-                    assigning = remaining == 1 and final_method == "assign"
-
-                    # Set the context, if appropriate.
-
-                    if remaining == 1 and final_method != "assign" and context == "final-accessor":
-
-                        # Invoked attributes employ a separate context accessed
-                        # during invocation.
-
-                        if final_method in ("access-invoke", "static-invoke"):
-                            emit(("<set_context>", accessor))
-                            accessor = context_var = "<context>"
-
-                        # A private context within the access is otherwise
-                        # retained.
-
-                        else:
-                            emit(("<set_private_context>", accessor))
-                            accessor = context_var = "<private_context>"
-
-                    # Perform the access only if not achieved directly.
-
-                    if remaining > 1 or final_method in ("access", "access-invoke", "assign"):
-
-                        # Constrain instructions involving certain special
-                        # attribute names.
-
-                        to_search = attrname != "__data__" and "any" or "object"
-
-                        if assigning:
-                            emit(("<set_attr_ref>", ("__check_and_get_object_attr_ref", accessor, attrname)))
-                            emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-                        else:
-                            accessor = ("__check_and_load_via_%s" % to_search, accessor, attrname)
-
-                    remaining -= 1
-
-            # Make any accessor test available if not emitted.
-
-            test_accessor = not instructions and test_accessor or None
-
-            # Define or emit the means of accessing the actual target.
-
-            if final_method in ("static", "static-assign", "static-invoke"):
-
-                if test_accessor:
-                    emit(test_accessor)
-
-                # Assignments to known attributes.
-
-                if final_method == "static-assign":
-                    parent, attrname = origin.rsplit(".", 1)
-                    emit(("<set_attr_ref>", ("__get_object_attr_ref", parent, attrname)))
-                    emit(("__store_via_attr_ref", "<attr_ref>", "<assexpr>"))
-
-                # Invoked attributes employ a separate context.
-
-                elif final_method in ("static", "static-invoke"):
-                    accessor = ("__load_static_ignore", origin)
-
-            # Define any replacement context variable plus the default eventual
-            # context variable.
-
-            replacement_context_var = "<new_context>"
-            final_context_var = context_var
-
-            # Wrap accesses in context operations.
-
-            if context_test == "test":
-
-                # Test and combine the context with static attribute details.
-
-                if final_method == "static":
-                    emit(("__load_static_test", replacement_context_var, context_var, origin))
-                    final_context_var = replacement_context_var
-
-                # Test the context, storing it separately if required for the
-                # immediately invoked static attribute.
-
-                elif final_method == "static-invoke":
-                    emit(("<test_context_static>", context_var, origin))
-
-                # Test the context, storing it separately if required for an
-                # immediately invoked attribute.
-
-                elif final_method == "access-invoke":
-                    emit(("<test_context_revert>", context_var, accessor))
-
-                # Test the context and update the attribute details if
-                # appropriate.
-
-                else:
-                    emit(("__test_context", replacement_context_var, context_var, accessor))
-                    final_context_var = replacement_context_var
-
-            elif context_test == "replace":
-
-                # Produce an object with updated context.
-
-                if final_method == "static":
-                    emit(("__load_static_replace", replacement_context_var, context_var, origin))
-                    final_context_var = replacement_context_var
-
-                # Omit the context update operation where the target is static
-                # and the context is recorded separately.
-
-                elif final_method == "static-invoke":
-                    pass
-
-                # If a separate context is used for an immediate invocation,
-                # produce the attribute details unchanged.
-
-                elif final_method == "access-invoke":
-                    emit(accessor)
-
-                # Update the context in the attribute details.
-
-                else:
-                    emit(("__update_context", replacement_context_var, context_var, accessor))
-                    final_context_var = replacement_context_var
-
-            # Omit the accessor for assignments and for invocations of static
-            # targets. Otherwise, emit the accessor which may involve the
-            # invocation of a test.
-
-            elif final_method not in ("assign", "static-assign", "static-invoke"):
-                emit(accessor)
-
-            # Produce an advisory instruction regarding the context.
-
-            if final_context_var:
-
-                # Only verify the context for invocation purposes if a suitable
-                # test has been performed.
-
-                if context_test in ("ignore", "replace") or \
-                   final_method in ("access-invoke", "static-invoke"):
-
-                    emit(("<context_identity_verified>", final_context_var))
-                else:
-                    emit(("<context_identity>", final_context_var))
-
-            # Produce an advisory instruction regarding the final attribute.
-
-            if origin:
-                emit(("<final_identity>", origin))
-
-            self.access_instructions[access_location] = instructions
-            self.accessor_kinds[access_location] = accessor_kinds
+            self.access_instructions[access_location] = access_plan.get_instructions()
+            self.accessor_kinds[access_location] = access_plan.accessor_kinds
 
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r f646afbcfe1c -r 582d834d392d docs/wiki/Deduction
--- a/docs/wiki/Deduction	Sun Sep 03 00:24:29 2023 +0200
+++ b/docs/wiki/Deduction	Tue Sep 05 21:16:49 2023 +0200
@@ -89,7 +89,7 @@
 //format=svg
 //transform=notugly
 digraph indexes {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Indexes"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Indexes"];
   edge [tooltip="Indexes"];
   rankdir=LR;
 
@@ -142,7 +142,7 @@
 //format=svg
 //transform=notugly
 digraph deduction {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Deduction"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Deduction"];
   edge [tooltip="Deduction"];
   rankdir=LR;
 
@@ -192,7 +192,7 @@
 //format=svg
 //transform=notugly
 digraph usage_to_types {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Usage to types"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Usage to types"];
   edge [tooltip="Usage to types"];
   rankdir=LR;
 
@@ -249,7 +249,7 @@
 //format=svg
 //transform=notugly
 digraph instance_providers {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Instance providers"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Instance providers"];
   edge [tooltip="Instance providers"];
   rankdir=LR;
 
@@ -310,7 +310,7 @@
 //format=svg
 //transform=notugly
 digraph assignments {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Attribute assignments"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Attribute assignments"];
   edge [tooltip="Attribute assignments"];
   rankdir=LR;
 
@@ -736,19 +736,34 @@
 .. position
 }}}
 
-==== Direct Store ====
+==== Attribute Reference ====
 
-These instructions employ the attribute position for the supplied attribute
-name, storing an attribute value.
+Attribute references are obtained to be targets for store operations as well
+as being exposed as result targets.
 
 {{{#!table
 '''Instruction''' || '''Arguments''' || '''Operations'''
 ==
-`__store_via_class` || object, attribute name, value
-|| Obtain class from object; store attribute in class at position
+`__get_class_attr_ref` || object, attribute name
+|| Obtain class from object; obtain reference for attribute in class
 ==
-`__store_via_object` || object, attribute name, value
-|| Store attribute in object at position
+`__get_object_attr_ref` || object, attribute name
+|| Obtain reference for attribute in object
+}}}
+
+==== Attribute Reference Load and Store ====
+
+These instructions employ an attribute reference, previously obtained for a
+given attribute in an object.
+
+{{{#!table
+'''Instruction''' || '''Arguments''' || '''Operations'''
+==
+`__load_via_attr_ref` || attribute reference
+|| Load value from attribute reference
+==
+`__store_via_attr_ref` || attribute reference, value
+|| Store value in attribute at reference
 }}}
 
 ==== Checked Load ====
@@ -770,7 +785,7 @@
 .. raise type error
 }}}
 
-==== Checked Store ====
+==== Checked Attribute Reference ====
 
 These instructions employ the attribute position and code for the supplied
 attribute name, storing an attribute value.
@@ -778,14 +793,8 @@
 {{{#!table
 '''Instruction''' || '''Arguments''' || '''Operations'''
 ==
-`__check_and_store_via_class` || object, attribute name, value
-|| Raise type error
-==
-`__check_and_store_via_object` || object, attribute name, value
-|| Test for attribute and store value or raise type error
-==
-`__check_and_store_via_any` || object, attribute name, value
-|| Test for attribute and store value or raise type error
+`__check_and_get_object_attr_ref` || object, attribute name
+|| Test for attribute and obtain reference or raise type error
 }}}
 
 ==== Testing ====
@@ -844,20 +853,29 @@
 {{{#!table
 '''Instruction''' || '''Arguments''' || '''Operations'''
 ==
-`__get_context` || (temporary)
-|| Load the context stored in the temporary storage
+`__get_accessor` || (temporary)
+|| Load the indicated accessor from temporary storage
+==
+`__get_attr_ref` || (temporary)
+|| Load the indicated attribute reference from temporary storage
 ==
-`__set_accessor` || accessor
-|| Store the accessor temporarily
+`__get_context` || (temporary)
+|| Load the indicated context from temporary storage
+==
+`__set_accessor` || (temporary), accessor
+|| Store the accessor in temporary storage
+==
+`__set_attr_ref` || (temporary), reference
+|| Store the given attribute reference in temporary storage
 ==
 `__set_context` || (temporary), context
-|| Store the context in the temporary storage
+|| Store the given context in temporary storage
 ==
 `__set_private_context` || context
-|| Store the context temporarily
+|| Store the context in temporary storage
 ==
 `__set_target_accessor` || accessor
-|| Store the assignment accessor temporarily
+|| Store the assignment accessor in temporary storage
 }}}
 
 ==== Context Test ====
diff -r f646afbcfe1c -r 582d834d392d docs/wiki/Imports
--- a/docs/wiki/Imports	Sun Sep 03 00:24:29 2023 +0200
+++ b/docs/wiki/Imports	Tue Sep 05 21:16:49 2023 +0200
@@ -95,7 +95,7 @@
 //format=svg
 //transform=notugly
 digraph mutual {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Mutually-dependent modules"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Mutually-dependent modules"];
   edge [tooltip="Mutually-dependent modules"];
   rankdir=LR;
 
@@ -209,7 +209,7 @@
 //format=svg
 //transform=notugly
 digraph imports {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Import dependencies"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Import dependencies"];
   edge [tooltip="Import dependencies"];
   rankdir=LR;
 
diff -r f646afbcfe1c -r 582d834d392d docs/wiki/Inspection
--- a/docs/wiki/Inspection	Sun Sep 03 00:24:29 2023 +0200
+++ b/docs/wiki/Inspection	Tue Sep 05 21:16:49 2023 +0200
@@ -179,7 +179,7 @@
 //format=svg
 //transform=notugly
 digraph accesses {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Names and accesses"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Names and accesses"];
   edge [tooltip="Names and accesses"];
   rankdir=TB;
 
@@ -316,7 +316,7 @@
 //format=svg
 //transform=notugly
 digraph usage {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Name and attribute tracking"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Name and attribute tracking"];
   edge [tooltip="Name and attribute tracking"];
   rankdir=TB;
 
diff -r f646afbcfe1c -r 582d834d392d docs/wiki/Representations
--- a/docs/wiki/Representations	Sun Sep 03 00:24:29 2023 +0200
+++ b/docs/wiki/Representations	Tue Sep 05 21:16:49 2023 +0200
@@ -16,8 +16,8 @@
 //format=svg
 //transform=notugly
 digraph attributes {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Attributes"];
-  edge [fontsize="13.0",fontname="sans-serif",tooltip="Attributes"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Attributes"];
+  edge [fontsize="12.0",fontname="sans-serif",tooltip="Attributes"];
   rankdir=TB;
 
   attrA [label="attribute | { value |<value> reference to object }",shape=record];
@@ -77,8 +77,8 @@
 //format=svg
 //transform=notugly
 digraph wrappers {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Wrappers"];
-  edge [fontsize="13.0",fontname="sans-serif",tooltip="Wrappers"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Wrappers"];
+  edge [fontsize="12.0",fontname="sans-serif",tooltip="Wrappers"];
   rankdir=TB;
 
   inst [label="<main> instance | { attr1 |<attr1> reference to method } | { attr2 | value } | ...",shape=record];
@@ -104,8 +104,8 @@
 //format=svg
 //transform=notugly
 digraph objects {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Objects"];
-  edge [fontsize="13.0",fontname="sans-serif",tooltip="Objects"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Objects"];
+  edge [fontsize="12.0",fontname="sans-serif",tooltip="Objects"];
   rankdir=TB;
 
   instC [label="<main> instance of C | { 0 | reference to\ninstance table } | { __class__ |<cls> reference\nto C } | { a | value } | { b | value } | ...",shape=record];
diff -r f646afbcfe1c -r 582d834d392d docs/wiki/Restarted
--- a/docs/wiki/Restarted	Sun Sep 03 00:24:29 2023 +0200
+++ b/docs/wiki/Restarted	Tue Sep 05 21:16:49 2023 +0200
@@ -262,8 +262,8 @@
 //format=svg
 //transform=notugly
 digraph structures {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Instance and class structures"];
-  edge [fontsize="13.0",fontname="sans-serif",tooltip="Instance and class structures"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Instance and class structures"];
+  edge [fontsize="12.0",fontname="sans-serif",tooltip="Instance and class structures"];
   rankdir=TB;
 
   instanceC [label="<main> instance of C |{ context of a | value of a }|{context of b | value of b }",shape=record];
@@ -285,8 +285,8 @@
 //format=svg
 //transform=notugly
 digraph methods {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Method structures"];
-  edge [fontsize="13.0",fontname="sans-serif",tooltip="Method structures"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Method structures"];
+  edge [fontsize="12.0",fontname="sans-serif",tooltip="Method structures"];
   rankdir=TB;
 
   classC [label="<main> class C | { context of m | <mvalue> uncallable for m } | ...",shape=record];
diff -r f646afbcfe1c -r 582d834d392d docs/wiki/Structure
--- a/docs/wiki/Structure	Sun Sep 03 00:24:29 2023 +0200
+++ b/docs/wiki/Structure	Tue Sep 05 21:16:49 2023 +0200
@@ -29,7 +29,7 @@
 //format=svg
 //transform=notugly
 digraph program {
-  node [shape=box,fontsize="13.0",fontname="sans-serif",tooltip="Program structure"];
+  node [shape=box,fontsize="12.0",fontname="sans-serif",tooltip="Program structure"];
   edge [tooltip="Program structure"];
   rankdir=LR;
 
diff -r f646afbcfe1c -r 582d834d392d templates/native/common.c
--- a/templates/native/common.c	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/native/common.c	Tue Sep 05 21:16:49 2023 +0200
@@ -30,9 +30,9 @@
 {
     /* Create a new string and mutate the __data__, __size__ and __key__ attributes. */
     __attr attr = __NEWINSTANCE(__builtins___str_str);
-    __store_via_attr_ref(__get_object_attr_ref(__VALUE(attr), __data__), (__attr) {.strvalue=s});
-    __store_via_attr_ref(__get_object_attr_ref(__VALUE(attr), __size__), __INTVALUE(size));
-    __store_via_attr_ref(__get_object_attr_ref(__VALUE(attr), __key__), __NULL);
+    __store_via_attr_ref__(__get_object_attr_ref(__VALUE(attr), __data__), (__attr) {.strvalue=s});
+    __store_via_attr_ref__(__get_object_attr_ref(__VALUE(attr), __size__), __INTVALUE(size));
+    __store_via_attr_ref__(__get_object_attr_ref(__VALUE(attr), __key__), __NULL);
     return attr;
 }
 
@@ -40,7 +40,7 @@
 {
     /* Create a new list and mutate the __data__ attribute. */
     __attr attr = __NEWINSTANCE(__builtins___list_list);
-    __store_via_attr_ref(__get_object_attr_ref(__VALUE(attr), __data__), (__attr) {.seqvalue=f});
+    __store_via_attr_ref__(__get_object_attr_ref(__VALUE(attr), __data__), (__attr) {.seqvalue=f});
     return attr;
 }
 
diff -r f646afbcfe1c -r 582d834d392d templates/native/list.c
--- a/templates/native/list.c	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/native/list.c	Tue Sep 05 21:16:49 2023 +0200
@@ -56,7 +56,7 @@
 
     /* Replace the __data__ attribute if appropriate. */
     if (newdata != data)
-        __store_via_attr_ref(__get_object_attr_ref(__VALUE(self), __data__), ((__attr) {.seqvalue=newdata}));
+        __store_via_attr_ref__(__get_object_attr_ref(__VALUE(self), __data__), ((__attr) {.seqvalue=newdata}));
     return __builtins___none_None;
 }
 
@@ -84,7 +84,7 @@
 
     /* Replace the __data__ attribute if appropriate. */
     if (newdata != data)
-        __store_via_attr_ref(__get_object_attr_ref(__VALUE(self), __data__), ((__attr) {.seqvalue=newdata}));
+        __store_via_attr_ref__(__get_object_attr_ref(__VALUE(self), __data__), ((__attr) {.seqvalue=newdata}));
     return __builtins___none_None;
 }
 
diff -r f646afbcfe1c -r 582d834d392d templates/ops.c
--- a/templates/ops.c	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/ops.c	Tue Sep 05 21:16:49 2023 +0200
@@ -417,7 +417,7 @@
 
 void *__ALLOCATEIM(size_t nmemb, size_t size)
 {
-    void *ptr = GC_MALLOC_ATOMIC(nmemb * size); /* sets memory to zero */
+    void *ptr = GC_MALLOC_ATOMIC(nmemb * size);
     if (ptr == NULL)
         __raise_memory_error();
     return ptr;
diff -r f646afbcfe1c -r 582d834d392d templates/ops.h
--- a/templates/ops.h	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/ops.h	Tue Sep 05 21:16:49 2023 +0200
@@ -46,6 +46,8 @@
 #define __load_via_attr_ref(ATTR) (*(ATTR))
 #define __store_via_attr_ref(ATTR, VALUE) __set_attr(ATTR, VALUE)
 
+#define __store_via_attr_ref__(ATTR, VALUE) (*(ATTR) = VALUE)
+
 /* Direct retrieval operations, returning attributes. */
 
 __attr __load_via_class__(__ref obj, int pos);
diff -r f646afbcfe1c -r 582d834d392d templates/progops.c
--- a/templates/progops.c	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/progops.c	Tue Sep 05 21:16:49 2023 +0200
@@ -32,7 +32,7 @@
 {
     obj->table = table;
     obj->pos = __INSTANCEPOS;
-    __store_via_attr_ref(__get_object_attr_ref(obj, __class__), __ATTRVALUE(cls));
+    __store_via_attr_ref__(__get_object_attr_ref(obj, __class__), __ATTRVALUE(cls));
 }
 
 __attr __new(const __table * table, __ref cls, size_t size, int immutable)
@@ -81,7 +81,7 @@
 
     /* Store a reference to the data in the object's __data__ attribute. */
 
-    __store_via_attr_ref(__get_object_attr_ref(__VALUE(self), __data__), (__attr) {.seqvalue=data});
+    __store_via_attr_ref__(__get_object_attr_ref(__VALUE(self), __data__), (__attr) {.seqvalue=data});
     __newdata_sequence(number, data, args);
     return self;
 }
@@ -97,7 +97,7 @@
 
     /* Store a reference to the data in the object's __data__ attribute. */
 
-    __store_via_attr_ref(__get_object_attr_ref(__VALUE(self), __data__), (__attr) {.seqvalue=data});
+    __store_via_attr_ref__(__get_object_attr_ref(__VALUE(self), __data__), (__attr) {.seqvalue=data});
     __newdata_sequence(number, data, args);
     return self;
 }
@@ -315,7 +315,7 @@
 
 void __SETDEFAULT(__ref obj, int pos, __attr value)
 {
-    __store_via_attr_ref(__get_object_attr_ref__(obj, __FUNCTION_INSTANCE_SIZE + pos), value);
+    __store_via_attr_ref__(__get_object_attr_ref__(obj, __FUNCTION_INSTANCE_SIZE + pos), value);
 }
 
 __attr __GETDEFAULT(__ref obj, int pos)
diff -r f646afbcfe1c -r 582d834d392d templates/progops.h
--- a/templates/progops.h	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/progops.h	Tue Sep 05 21:16:49 2023 +0200
@@ -91,6 +91,6 @@
 /* Operations for accessing trailing data. */
 
 #define __get_trailing_data(ATTR, TYPE) (((__OBJTYPE(TYPE) *) ((ATTR).value))->trailing)
-#define __set_trailing_data(ATTR, TYPE, VALUE) ((__OBJTYPE(TYPE) *) ((ATTR).value))->trailing = VALUE;
+#define __set_trailing_data(ATTR, TYPE, VALUE) ((__OBJTYPE(TYPE) *) ((ATTR).value))->trailing = VALUE
 
 #endif /* __PROGOPS_H__ */
diff -r f646afbcfe1c -r 582d834d392d templates/types.h
--- a/templates/types.h	Sun Sep 03 00:24:29 2023 +0200
+++ b/templates/types.h	Tue Sep 05 21:16:49 2023 +0200
@@ -115,8 +115,6 @@
 
 } __obj;
 
-#define __INSTANCE_SIZE(NUMBER) ((NUMBER) * sizeof(__attr) + sizeof(__table *) + sizeof(__ppos))
-
 /* Fragments are simple collections of attributes employed by sequence types.
    They provide the basis of lists and tuples. */
 
diff -r f646afbcfe1c -r 582d834d392d tests/values.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/values.py	Tue Sep 05 21:16:49 2023 +0200
@@ -0,0 +1,7 @@
+def test(a):
+    a = a - 1.0
+    return a
+
+x = 2.0
+print test(x)               # 1.0
+print x                     # 2.0
diff -r f646afbcfe1c -r 582d834d392d translator.py
--- a/translator.py	Sun Sep 03 00:24:29 2023 +0200
+++ b/translator.py	Tue Sep 05 21:16:49 2023 +0200
@@ -1766,9 +1766,17 @@
         # objects, with only floats supporting replaceable values.
 
         if expr:
-            target_ref = TrResolvedNameRef(n.name, ref, is_global=is_global,
-                                           location=location)
-            self.result_target_name = str(target_ref)
+            # Prevent parameters from becoming result targets. Otherwise, they
+            # may inadvertently cause the modification of the supplied object.
+
+            parameters = self.importer.function_parameters.get(path)
+
+            if not parameters or n.name not in parameters:
+                target_ref = TrResolvedNameRef(n.name, ref, is_global=is_global,
+                                               location=location)
+                self.result_target_name = str(target_ref)
+            else:
+                self.result_target_name = None
 
         # Expression processing is deferred until after any result target has
         # been set.
diff -r f646afbcfe1c -r 582d834d392d transresults.py
--- a/transresults.py	Sun Sep 03 00:24:29 2023 +0200
+++ b/transresults.py	Tue Sep 05 21:16:49 2023 +0200
@@ -101,6 +101,8 @@
 
         if self.expr:
 
+            store = self.attrname != "__data__" and "__store_via_attr_ref" or "__store_via_attr_ref__"
+
             # Eliminate assignments between constants.
 
             if self.static_ref and self.expr.static():
@@ -109,14 +111,14 @@
             # Qualified names must be converted into parent-relative assignments.
 
             elif self.parent:
-                return "__store_via_attr_ref(__get_object_attr_ref(&%s, %s), %s)" % (
-                    encode_path(self.parent), self.attrname, self.expr)
+                return "%s(__get_object_attr_ref(&%s, %s), %s)" % (
+                    store, encode_path(self.parent), self.attrname, self.expr)
 
             # All other assignments involve the names as they were given.
             # To support value replacement, a special operation is used.
 
             else:
-                return "__set_attr(&%s, %s)" % (self.attrname, self.expr)
+                return "%s(&%s, %s)" % (store, self.attrname, self.expr)
 
         # Expressions.