# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1487445227 -3600
# Node ID 767f7ac69ef2d2e6e69f045dc2866f90a88695d6
# Parent  3e5b14c95a551054e7298186c5257c465b2268fb
Introduced a context test that sets a local context where an attribute is
invoked immediately.

diff -r 3e5b14c95a55 -r 767f7ac69ef2 encoders.py
--- a/encoders.py	Sat Feb 18 18:52:04 2017 +0100
+++ b/encoders.py	Sat Feb 18 20:13:47 2017 +0100
@@ -215,7 +215,7 @@
     )
 
 context_ops = (
-    "<context>", "<set_context>",
+    "<context>", "<set_context>", "<test_context>",
     )
 
 reference_acting_ops = attribute_ops + checked_ops + typename_ops
diff -r 3e5b14c95a55 -r 767f7ac69ef2 optimiser.py
--- a/optimiser.py	Sat Feb 18 18:52:04 2017 +0100
+++ b/optimiser.py	Sat Feb 18 20:13:47 2017 +0100
@@ -533,6 +533,8 @@
             if context_test == "test":
                 if final_method in ("static", "static-invoke"):
                     emit(("__load_static_test", context_var, origin))
+                elif final_method == "access-invoke":
+                    emit(("<test_context>", context_var, accessor))
                 else:
                     emit(("__test_context", context_var, accessor))
 
diff -r 3e5b14c95a55 -r 767f7ac69ef2 templates/ops.c
--- a/templates/ops.c	Sat Feb 18 18:52:04 2017 +0100
+++ b/templates/ops.c	Sat Feb 18 20:13:47 2017 +0100
@@ -198,14 +198,16 @@
 
 /* Context-related operations. */
 
-__attr __test_context(__ref context, __attr attr)
+int __test_context_update(__ref context, __attr attr)
 {
+    /* Return whether the context should be updated for the attribute. */
+
     __ref attrcontext = __CONTEXT_AS_VALUE(attr).value;
 
     /* Preserve any existing null or instance context. */
 
     if ((attrcontext == 0) || __is_instance(attrcontext))
-        return attr;
+        return 0;
 
     /* Test any instance context against the context employed by the
        attribute. */
@@ -213,7 +215,7 @@
     if (__is_instance(context))
     {
         if (__test_common_instance(context, __TYPEPOS(attrcontext), __TYPECODE(attrcontext)))
-            return __update_context(context, attr);
+            return 1;
         else
             __raise_type_error();
     }
@@ -221,11 +223,21 @@
     /* Test for access to a type class attribute using a type instance. */
 
     if (__test_specific_type(attrcontext, &__TYPE_CLASS_TYPE) && __is_type_instance(context))
-        return __update_context(context, attr);
+        return 1;
 
     /* Otherwise, preserve the attribute as retrieved. */
 
-    return attr;
+    return 0;
+}
+
+__attr __test_context(__ref context, __attr attr)
+{
+    /* Update the context or return the unchanged attribute. */
+
+    if (__test_context_update(context, attr))
+        return __update_context(context, attr);
+    else
+        return attr;
 }
 
 __attr __update_context(__ref context, __attr attr)
diff -r 3e5b14c95a55 -r 767f7ac69ef2 templates/ops.h
--- a/templates/ops.h	Sat Feb 18 18:52:04 2017 +0100
+++ b/templates/ops.h	Sat Feb 18 20:13:47 2017 +0100
@@ -70,9 +70,13 @@
 
 /* Context-related operations. */
 
+int __test_context_update(__ref context, __attr attr);
 __attr __test_context(__ref context, __attr attr);
 __attr __update_context(__ref context, __attr attr);
 
+#define __test_context_set(__TARGET, __CONTEXT, __ATTR) \
+        (__test_context_update(__CONTEXT, __ATTR) ? (__set_context(__TARGET, (__attr) {.value=__CONTEXT}), __ATTR) : __ATTR)
+
 #define __get_context(__TARGET) (__tmp_contexts[__TARGET])
 #define __set_context(__TARGET, __ATTR) (__tmp_contexts[__TARGET] = (__ATTR).value)
 #define __set_private_context(__ATTR) (__tmp_private_context = (__ATTR).value)
diff -r 3e5b14c95a55 -r 767f7ac69ef2 translator.py
--- a/translator.py	Sat Feb 18 18:52:04 2017 +0100
+++ b/translator.py	Sat Feb 18 20:13:47 2017 +0100
@@ -789,6 +789,7 @@
             # Mappings to be replaced by those given below.
 
             "<context>" : "__tmp_contexts",
+            "<test_context>" : "__tmp_contexts",
             "<set_context>" : "__tmp_contexts",
             "<set_private_context>" : "__tmp_private_context",
             "<set_accessor>" : "__tmp_value",
@@ -797,6 +798,7 @@
 
         self.op_subs = {
             "<context>" : "__get_context",
+            "<test_context>" : "__test_context_set",
             "<set_context>" : "__set_context",
             "<set_private_context>" : "__set_private_context",
             "<set_accessor>" : "__set_accessor",