Extending "contradiction" so that it recognizes statements such as "~x=x" or ~True.

Found 1 incompatibility in tested contribs and 3 times the same
pattern of incompatibility in the standard library. In all cases, it
is an improvement in the form of the script.

New behavior deactivated when version is <= 8.5.

1 files changed, 4 insertions, 4 deletions

diff --git a/doc/refman/RefMan-tac.tex b/doc/refman/RefMan-tac.tex
index 8172b5771..65b49893b 100644
--- a/doc/refman/RefMan-tac.tex
+++ b/doc/refman/RefMan-tac.tex
@@ -1491,10 +1491,10 @@ the local context.
 \tacindex{contradiction}
 
 This tactic applies to any goal. The {\tt contradiction} tactic
-attempts to find in the current context (after all {\tt intros}) one
-hypothesis that is equivalent to {\tt False}. It permits to prune
-irrelevant cases. This tactic is a macro for the tactics sequence
-{\tt intros; elimtype False; assumption}.
+attempts to find in the current context (after all {\tt intros}) an
+hypothesis that is equivalent to an empty inductive type (e.g. {\tt
+  False}), to the negation of a singleton inductive type (e.g. {\tt
+  True} or {\tt x=x}), or two contradictory hypotheses.
 
 \begin{ErrMsgs}
 \item \errindex{No such assumption}