swift234

Change ASTWalker to preserve AbstractFunctionDecl body kinds when walking.

This commit changes ASTWalker to preserve AbstractFunctionDecl body kinds. When
walking over an AbstractFunctionDecl, ASTWalker calls setBody() on the
declaration to update the body after traversal. Prior to this commit, setBody()
would unconditionally set the body kind to BodyKind::Parsed --- that is,
traversing the AST would change the body kind to Parsed. In some cases, this
modified a body kind from TypeChecked to Parsed, causing a small number of
standard library functions to be type checked twice. This behavior also
interferes with the creation of type refinement contexts for variable accessor
functions (coming in a future commit).

This commit adds an additional parameter to setBody() that allows callers to
provide a body kind (this defaults to Parsed) and changes ASTWalker to preserve
the body kind when walking a AbstractFunctionDecl.



Swift SVN r22607