tcc_statement vs. tcc_expression in the C++ frontend

[Nathan Sidwell]

Ian Lance Taylor wrote:
> The description of tcc_statement in tree.h says "A statement
> expression, which have side effects but usually no interesting value."
> 
> There are a number of entries in cp/cp-tree.def which are marked as
> tcc_expression, although they seem to me to be better described as
> tcc_statement, to wit:


> In a quick look at the C++ front end, I can only find one bit of code
> which cares whether it is looking at a tcc_expression or a
> tcc_statement: value_dependent_expression_p in pt.c.  That function
> will always return false for a statement.  For all of the tree codes
> listed above, currently class tcc_expression, the function will call
> itself recursively on expression operands.  I haven't tried to track
> all the calls to see whether any of the above codes can be passed to
> value_dependent_expression_p, but it doesn't seem likely.

None of the statement nodes you mention can be value dependent.  If
that's the only place that cares, they should be tcc_statement.

> Anyhow, I'm testing the obvious patch to use tcc_statement instead of
> tcc_expression in cp-tree.def, and I will submit it to gcc-patches if
> it works.  At the moment I'm curious as to whether anybody has a
> reason why these codes should be tcc_expression rather than
> tcc_statement.
I cannot think of any.

nathan
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