add custom error for 'catch (my $e)'

op.c

@@ -4141,7 +4141,7 @@ S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
         } else if (attrs) {
             GV * const gv = cGVOPx_gv(cUNOPo->op_first);
             assert(PL_parser);
-            PL_parser->in_my = FALSE;
+            PL_parser->in_my = KEY_NULL;
             PL_parser->in_my_stash = NULL;
             apply_attrs(GvSTASH(gv),
                         (type == OP_RV2SV ? GvSVn(gv) :
@@ -4174,7 +4174,7 @@ S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
         HV *stash;
 
         assert(PL_parser);
-        PL_parser->in_my = FALSE;
+        PL_parser->in_my = KEY_NULL;
         PL_parser->in_my_stash = NULL;
 
         /* check for C<my Dog $spot> when deciding package */
@@ -4232,7 +4232,7 @@ Perl_my_attrs(pTHX_ OP *o, OP *attrs)
             o = op_append_list(OP_LIST, o, rops);
         }
     }
-    PL_parser->in_my = FALSE;
+    PL_parser->in_my = KEY_NULL;
     PL_parser->in_my_stash = NULL;
     return o;
 }
@@ -4857,7 +4857,7 @@ Perl_localize(pTHX_ OP *o, I32 lex)
         o = my(o);
     else
         o = op_lvalue(o, OP_NULL);		/* a bit kludgey */
-    PL_parser->in_my = FALSE;
+    PL_parser->in_my = KEY_NULL;
     PL_parser->in_my_stash = NULL;
     return o;
 }

perly.y

@@ -289,7 +289,7 @@ catch_paren:	empty
 			/* not really valid grammar but we detect it in the
 			 * action block to throw a nicer error message */
 	|	PERLY_PAREN_OPEN
-			{ parser->in_my = 1; }
+			{ parser->in_my = KEY_catch; }
 		scalar
 			{ parser->in_my = 0; intro_my(); }
 		PERLY_PAREN_CLOSE

pod/perldelta.pod

@@ -198,6 +198,22 @@ and L</New Warnings>
 
 XXX L<message|perldiag/"message">
 
+=item *
+
+L<Can't redeclare catch variable as "%s"|perldiag/"Can't redeclare catch variable as "%s"">
+
+(F) A C<my>, C<our> or C<state> keyword was used with the exception variable in
+a C<catch> block:
+
+    try { ... }
+    catch (my $e) { ... }
+    # or catch (our $e) { ... }
+    # or catch (state $e) { ... }
+
+This is not valid syntax. C<catch> takes a bare variable name, which is
+automatically lexically declared.
+[GH #23222]
+
 =back
 
 =head3 New Warnings

pod/perldiag.pod

@@ -1485,10 +1485,23 @@ missing.  You need to figure out where your CRTL misplaced its environ
 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not
 searched.
 
+=item Can't redeclare catch variable as "%s"
+
+(F) A C<my>, C<our> or C<state> keyword was used with the exception variable in
+a C<catch> block:
+
+    try { ... }
+    catch (my $e) { ... }
+    # or catch (our $e) { ... }
+    # or catch (state $e) { ... }
+
+This is not valid syntax. C<catch> takes a bare variable name, which is
+automatically lexically declared.
+
 =item Can't redeclare "%s" in "%s"
 
-(F) A "my", "our" or "state" declaration was found within another declaration,
-such as C<my ($x, my($y), $z)> or C<our (my $x)>.
+(F) A C<my>, C<our> or C<state> declaration was found within another
+declaration, such as C<my ($x, my($y), $z)> or C<our (my $x)>.
 
 =item Can't "redo" outside a loop block
 

t/lib/croak/toke

@@ -423,6 +423,30 @@ EXPECT
 Can't redeclare "state" in "state" at - line 2, near ", state"
 Execution of - aborted due to compilation errors.
 ########
+# NAME catch (my $x) errors
+use feature 'try';
+try {} catch (my $x) {}
+EXPECT
+Can't redeclare catch variable as "my" at - line 2, near "(my"
+syntax error at - line 2, near "(my "
+Execution of - aborted due to compilation errors.
+########
+# NAME catch (our $x) errors
+use feature 'try';
+try {} catch (our $x) {}
+EXPECT
+Can't redeclare catch variable as "our" at - line 2, near "(our"
+syntax error at - line 2, near "(our "
+Execution of - aborted due to compilation errors.
+########
+# NAME catch (state $x) errors
+use feature 'try', 'state';
+try {} catch (state $x) {}
+EXPECT
+Can't redeclare catch variable as "state" at - line 2, near "(state"
+syntax error at - line 2, near "(state "
+Execution of - aborted due to compilation errors.
+########
 # NAME BEGIN <> [perl #125341]
 BEGIN <>
 EXPECT

toke.c

@@ -7186,17 +7186,37 @@ yyl_do(pTHX_ char *s, I32 orig_keyword)
     OPERATOR(KW_DO);
 }
 
+static const char *
+declarator_name(I32 k) {
+    switch (k) {
+        case KEY_my:    return "my";
+        case KEY_state: return "state";
+        case KEY_our:   return "our";
+        case KEY_field: return "field";
+        case KEY_catch: return "catch";
+        default: return "???";
+    }
+}
+
 static int
 yyl_my(pTHX_ char *s, I32 my)
 {
+    assert(my == KEY_my || my == KEY_state || my == KEY_our);
     if (PL_in_my) {
         PL_bufptr = s;
-        yyerror(form(
-                          "Can't redeclare \"%s\" in \"%s\"",
-                           my       == KEY_my    ? "my" :
-                           my       == KEY_state ? "state" : "our",
-                           PL_in_my == KEY_my    ? "my" :
-                           PL_in_my == KEY_state ? "state" : "our"));
+        if (PL_in_my == KEY_catch) {
+            yyerror(form(
+                "Can't redeclare catch variable as \"%s\"",
+                    declarator_name(my)
+            ));
+        } else {
+            assert(PL_in_my == KEY_my || PL_in_my == KEY_state || PL_in_my == KEY_our);
+            yyerror(form(
+                "Can't redeclare \"%s\" in \"%s\"",
+                    declarator_name(my),
+                    declarator_name(PL_in_my)
+            ));
+        }
     }
     PL_in_my = (U16)my;
     s = skipspace(s);