[Voted into the WP at the March, 2011 meeting as part of paper N3268.]

Rationale (July, 2009):

This suggestion needs a proposal and analysis by EWG before it can be considered by CWG.

According to 9.2.6 [dcl.constexpr] paragraph 3, no declarations are permitted in the body of a constexpr function. This seems overly restrictive. At least three kinds of declarations would seem to be helpful in writing such functions: static_assert, typedef and alias declarations, and local automatic variables initialized with constant expressions. (Similar considerations apply to lambdas in which the lambda-return-type-clause is omitted.)