First declosure impl

docs/declass_algo.txt

@@ -175,16 +175,29 @@ Swap, CallMethod, PutLoc1, Drop) still occur elsewhere for ordinary reasons.
 Only the specific class-pattern instances listed above are removed.
 
 
+====================================================================
+UNSUPPORTED (the pass panics)
+====================================================================
+
+    DefineClass AtomU8 { arg: 1 }        derived class (extends)
+
+    Prototype form would have to flatten the parent's prototype into the
+    child's and lower `super`. Neither is implemented, so declass panics
+    rather than emit a class that has silently lost its parent.
+
+
 ====================================================================
 NOT TOUCHED (passed through unchanged)
 ====================================================================
 
-    DefineClass AtomU8 { arg: 1 }        derived class
-    DefineMethod AtomU8 { arg: 1 }       getter
-    DefineMethod AtomU8 { arg: 2 }       setter
     DefineMethodComputed ...             computed method name
     DefineClassComputed ...              computed class name
 
+    Known gap: a getter or setter (DefineMethod with a non-zero kind) is
+    NOT yet passed through. It is wrongly lowered as an ordinary method,
+    to a put_field, giving a data property instead of an accessor. It
+    should instead make the whole class pass through untouched.
+
 
 ====================================================================
 LEFT BEHIND (removed by a later pass)

docs/declosure_algo.txt

@@ -120,8 +120,12 @@ last argument, so it is args.last().
 
 DETECT, abstractly:
 
-    plain call   call | call0..3         (callee = last arg; not call_method,
-                                          call_constructor, or apply)
+    plain call   call | call0..3 | tail_call   (callee = last arg; not
+                                               call_method, call_constructor,
+                                               or apply)
+
+    A tail call stays a tail call. It pushes nothing and returns, so turning it
+    into an ordinary call would leave a value behind and drop the return.
 
 outer, which in the example is: