# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1481392374 -3600
# Node ID 22cf1ce6cfa74975b16025dfef57d84025846f70
# Parent  853edfa770e31cfb5880c0f3e3d7597719bab967
Introduced a separate variable for assignment accessors, preventing conflicts
between assignment targets and assignment expressions.

diff -r 853edfa770e3 -r 22cf1ce6cfa7 optimiser.py
--- a/optimiser.py	Sat Dec 10 17:35:58 2016 +0100
+++ b/optimiser.py	Sat Dec 10 18:52:54 2016 +0100
@@ -375,6 +375,8 @@
             # 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.
 
@@ -385,8 +387,8 @@
                 # Prevent re-evaluation of any dynamic expression by storing it.
 
                 if original_accessor == "<expr>":
-                    emit(("__set_accessor", original_accessor))
-                    accessor = context_var = ("<accessor>",)
+                    emit((set_accessor, original_accessor))
+                    accessor = context_var = (stored_accessor,)
                 else:
                     accessor = context_var = (original_accessor,)
 
@@ -397,8 +399,8 @@
                 # Prevent re-evaluation of any dynamic expression by storing it.
 
                 if original_accessor == "<expr>":
-                    emit(("__set_accessor", original_accessor))
-                    accessor = ("<accessor>",)
+                    emit((set_accessor, original_accessor))
+                    accessor = (stored_accessor,)
                 else:
                     accessor = (original_accessor,)
 
diff -r 853edfa770e3 -r 22cf1ce6cfa7 templates/ops.h
--- a/templates/ops.h	Sat Dec 10 17:35:58 2016 +0100
+++ b/templates/ops.h	Sat Dec 10 18:52:54 2016 +0100
@@ -73,6 +73,7 @@
 
 #define __set_context(__ATTR) (__tmp_context = (__ATTR).value)
 #define __set_accessor(__ATTR) (__tmp_value = (__ATTR).value)
+#define __set_target_accessor(__ATTR) (__tmp_target_value = (__ATTR).value)
 
 /* Basic structure tests. */
 
diff -r 853edfa770e3 -r 22cf1ce6cfa7 translator.py
--- a/translator.py	Sat Dec 10 17:35:58 2016 +0100
+++ b/translator.py	Sat Dec 10 18:52:54 2016 +0100
@@ -647,20 +647,7 @@
 
     def process_attribute_access(self, n):
 
-        """
-        Process the given attribute access node 'n'.
-
-        Where a name is provided, a single access should be recorded
-        involving potentially many attributes, thus providing a path to an
-        object. The remaining attributes are then accessed dynamically.
-        The remaining accesses could be deduced and computed, but they would
-        also need to be tested.
-
-        Where no name is provided, potentially many accesses should be
-        recorded, one per attribute name. These could be used to provide
-        computed accesses, but the accessors would need to be tested in each
-        case.
-        """
+        "Process the given attribute access node 'n'."
 
         # Obtain any completed chain and return the reference to it.
 
@@ -684,6 +671,7 @@
             "<assexpr>" : str(self.in_assignment),
             "<context>" : "__tmp_context",
             "<accessor>" : "__tmp_value",
+            "<target_accessor>" : "__tmp_target_value",
             }
 
         output = []
@@ -1687,7 +1675,7 @@
 
         targets = targets is not None and "__tmp_targets[%d], " % targets or ""
 
-        self.writeline("__ref __tmp_context, __tmp_value;")
+        self.writeline("__ref __tmp_context, __tmp_value, __tmp_target_value;")
         self.writeline("__attr %s__tmp_result;" % targets)
         self.writeline("__exc __tmp_exc;")