[Compiler-sig] Assign nodes

[Jeremy Hylton]

It looks like the code generator, as you mentioned, has to distinguish
between store and del anyway.  So getting rid of the special case for
load, just means making it a three part default test.

As it happens, the case of names is handled by three separate methods
-- loadName(), storeName(), and delName() -- that are called from the
visitor.  So the separate node types doesn't really buy anything.

Does the following patch look good?

Jeremy

Index: python.asdl
===================================================================
RCS file: /cvsroot/python/python/nondist/sandbox/ast/python.asdl,v
retrieving revision 1.12
diff -c -c -r1.12 python.asdl
*** python.asdl	16 Apr 2002 03:20:45 -0000	1.12
--- python.asdl	16 Apr 2002 16:43:55 -0000
***************
*** 8,16 ****
  	      | ClassDef(identifier name, expr* bases, stmt* body)
  	      | Return(expr value) | Yield(expr value)
  
! 	      | Del(assign* targets)
! 	      | Assign(assign* targets, expr value)
! 	      | AugAssign(assign target, operator op, expr value)
  
  	      -- not sure if bool is allowed, can always use int
   	      | Print(expr? dest, expr* value, bool nl)
--- 8,16 ----
  	      | ClassDef(identifier name, expr* bases, stmt* body)
  	      | Return(expr value) | Yield(expr value)
  
! 	      | Del(expr* targets)
! 	      | Assign(expr* targets, expr value)
! 	      | AugAssign(expr target, operator op, expr value)
  
  	      -- not sure if bool is allowed, can always use int
   	      | Print(expr? dest, expr* value, bool nl)
***************
*** 55,71 ****
  	     | Num(string n) -- string representation of a number
  	     | Str(string s) -- need to specify raw, unicode, etc?
  	     -- other literals? bools?
! 	     | Attribute(expr value, identifier attr)
! 	     | Subscript(expr value, slice slice)
! 	     | Name(identifier id)
! 	     | List(expr* elts) | Tuple(expr *elts)
! 
! 	-- the subset of expressions that are valid as the target of
! 	-- assignments. 
! 	assign = AssignAttribute(expr value, identifier attr)
! 	     | AssignSubscript(expr value, slice slice)
! 	     | AssignName(identifier id)
! 	     | AssignList(expr* elts) | AssignTuple(expr *elts)
  
          slice = Ellipsis | Slice(expr? lower, expr? upper) 
  	      -- maybe Slice and ExtSlice should be merged...
--- 55,69 ----
  	     | Num(string n) -- string representation of a number
  	     | Str(string s) -- need to specify raw, unicode, etc?
  	     -- other literals? bools?
! 
! 	     -- the following expression can appear in assignment context
! 	     | Attribute(expr value, identifier attr, expr_context ctx)
! 	     | Subscript(expr value, slice slice, expr_context ctx)
! 	     | Name(identifier id, expr_context ctx)
! 	     | List(expr* elts, expr_context ctx) 
! 	     | Tuple(expr *elts, expr_context ctx)
! 
! 	expr_context = Load | Store | Del
  
          slice = Ellipsis | Slice(expr? lower, expr? upper) 
  	      -- maybe Slice and ExtSlice should be merged...
***************
*** 84,90 ****
  
  	-- not sure what to call the first argument for raise and except
  
! 	except = (expr? type, assign? name, stmt* body)
  
  	-- XXX need to handle 'def f((a, b)):'
  	arguments = (identifier* args, identifier? vararg, 
--- 82,88 ----
  
  	-- not sure what to call the first argument for raise and except
  
! 	except = (expr? type, expr? name, stmt* body)
  
  	-- XXX need to handle 'def f((a, b)):'
  	arguments = (identifier* args, identifier? vararg,