conformance: handle macro wrong clause syntax.

Contrary to the documentation, handle doesn't in fact have the
same syntax as catch. It passes the exception symbol to
clauses as the leftmost argument, followed by the exception
arguments, whereas catch passes only the exception arguments.

* share/txr/stdlib/except.tl (handle): Do not pass the
exception sybmol as the leftmost argument, unless operating
in TXR 161 or earlier compatibility.

* tests/012/except.tl: drop exception symbol argument from
handle clause.

* txr.1: Compatibility note added.

1 files changed, 21 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index e422faf3..507d3f0a 100644
--- a/txr.1
+++ b/txr.1
@@ -50389,6 +50389,27 @@ of these version values, the described behaviors are provided if
 is given an argument which is equal or lower. For instance
 .code "-C 103"
 selects the behaviors described below for version 105, but not those for 102.
+.IP 161
+Version 161 was the last version in which a bug existed in the
+.code handle
+macro. In spite of the documentation claiming that
+.code handle
+has the same syntax as
+.codn catch ,
+the clauses of
+.code handle
+were being passed the exception symbol as the leftmost argument, followed
+by the exception arguments. This convention is different from
+.code catch
+clauses which do not receive the exception symbol, only the arguments.
+The discrepancy was corrected by making
+.code handle
+behave like
+.codn catch ,
+as documented. Requesting compatibility with 161 or earlier restores
+the previous behavior of the
+.code handle
+macro.
 .IP 156
 After version 156, two behaviors changed in the in the macro expander for
 .codn caseq ,