ParseXS: refactor: rationalise parse-fail action

Now that the XS parser builds a parse tree (AST), it spends most of its
time doing recursive-descent $some_node_object->parse() calls.

There is a common idiom within the current code along the lines of

    $some_node_object->parse()
        or return;

This makes a parse failure in a node propagate its way back up the call
chain. Note that many parse failures don't immediately croak; they
call blurt() which only warns, but also increments the error count;
parsing can continue.

During my big refactoring I haven't been entirely consistent here; this
commit adds a bunch of 'or return's that I missed. It also does a few
'or next's at higher levels, to get behaviour along the lines of:
"this XSUB had a syntax error, but continue trying to parse other XSUBs,
and only error out at the end."

This is all a bit going on gut feelings; in the final analysis it
doesn't matter too much how much more parsing gets done before xsubpp
finally croaks out.

Author: iabyn

dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS/Node.pm

@@ -552,7 +552,8 @@ sub parse {
 
     my $cpp_scope = ExtUtils::ParseXS::Node::cpp_scope->new({type => 'main'});
     $self->{cpp_scope} = $cpp_scope;
-    $cpp_scope->parse($pxs);
+    $cpp_scope->parse($pxs)
+        or return;
     push @{$self->{kids}}, $cpp_scope;
 
     # Now at EOF: all paragraphs (and thus XSUBs) have now been read in
@@ -1092,7 +1093,8 @@ sub parse {
 
         if ($pxs->{line}[0] =~ /^#/) {
             my $node = ExtUtils::ParseXS::Node::global_cpp_line->new();
-            $node->parse($pxs);
+            $node->parse($pxs)
+                or next;
             push @{$self->{kids}}, $node;
 
             next unless $node->{is_cond};
@@ -1121,7 +1123,7 @@ sub parse {
                 my $scope = ExtUtils::ParseXS::Node::cpp_scope->new(
                                                 {type => 'if'});
                 $scope->parse($pxs)
-                    or return 1;
+                    or next;
 
                 # Sub-parsing of that branch should have terminated
                 # at an elif/endif line rather than falling off the
@@ -1910,7 +1912,8 @@ sub parse {
         # Parse the XSUB's body
 
         my $xbody = ExtUtils::ParseXS::Node::xbody->new();
-        $xbody->parse($pxs, $self);
+        $xbody->parse($pxs, $self)
+            or return;
 
         if (defined $case) {
             # make the xbody a child of the CASE
@@ -2306,7 +2309,8 @@ sub parse {
 
     my $params = $self->{params} = ExtUtils::ParseXS::Node::Params->new();
 
-    $params->parse($pxs, $xsub, $params_text);
+    $params->parse($pxs, $xsub, $params_text)
+        or return;
     $self->{params} = $params;
     push @{$self->{kids}}, $params;
 
@@ -4351,7 +4355,8 @@ sub parse {
 
     my $autocall = ExtUtils::ParseXS::Node::autocall->new();
     # mainly a NOOP, but sets line number etc and flags that autocall seen
-    $autocall->parse($pxs, $xsub, $xbody);
+    $autocall->parse($pxs, $xsub, $xbody)
+        or return;
     push @{$self->{kids}}, $autocall;
 
     1;
@@ -5048,7 +5053,8 @@ sub parse {
                         type   => 'include',
                         is_cmd =>  $self->{is_cmd},
                     });
-    $cpp_scope->parse($pxs);
+    $cpp_scope->parse($pxs)
+        or return;
     push @{$self->{kids}}, $cpp_scope;
 
     --$pxs->{IncludedFiles}->{$pxs->{in_filename}}