PURE_ONCE_ASM_REWRITE_RULE : (thm list -> thm -> thm)
Rewrites a theorem once, including the theorem’s assumptions as rewrites.
PURE_ONCE_ASM_REWRITE_RULE excludes the basic tautologies in
implicit_rewrites from the theorems used for rewriting. It searches for
matching subterms once only, without recursing over already rewritten
subterms. For a general introduction to rewriting tools see
PURE_ONCE_ASM_REWRITE_RULE does not fail and does not diverge.