fix Issue 3735 - op=

expression.dd

@@ -117,16 +117,22 @@ $(V2
         Assignment operator expressions, such as:
 
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-$(I a op= b)
+a $(I op)= b
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         are semantically equivalent to:
 
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-$(I a = a op b)
+a = cast(typeof(a))(a $(I op) b)
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-        except that operand $(I a) is only evaluated once.
+        $(P except that:)
+
+	$(UL
+	$(LI operand $(D a) is only evaluated once)
+	$(LI overloading $(I op) uses a different function than overloading $(I op)= does)
+	$(LI the left operand of $(D >>>=) does not undergo integral promotions before shifting)
+	)
 
 <h2>Conditional Expressions</h2>