ParseXS - allow symbolic alias of default function

Also normalize warnings. It used to be if you created an alias
of the root function (0) no warning would be produced. Now
we will produce a warning, but we also allow symbolic references
to defuse the warning.

Author: demerphq

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

@@ -1311,6 +1311,9 @@ sub get_aliases {
   my ($line) = @_;
   my ($orig) = $line;
 
+  # we use this later for symbolic aliases
+  my $fname = $self->{Packprefix} . $self->{func_name};
+
   # Parse alias definitions
   # format is
   #    alias = value Pack::alias = value ...
@@ -1335,10 +1338,13 @@ sub get_aliases {
     if ($is_symbolic) {
       my $orig_value = $value;
       $value = $self->{Packprefix} . $value if $value !~ /::/;
-      if (!defined $self->{XsubAliases}->{$value}) {
+      if (defined $self->{XsubAliases}->{$value}) {
+        $value = $self->{XsubAliases}->{$value};
+      } elsif ($value eq $fname) {
+        $value = 0;
+      } else {
         blurt( $self, "Error: Unknown alias '$value' in symbolic definition for '$orig_alias'");
       }
-      $value = $self->{XsubAliases}->{$value};
     }
 
     # check for duplicate alias name & duplicate value
@@ -1359,12 +1365,19 @@ sub get_aliases {
     # it is NOT a mistake.
     unless ($is_symbolic) {
       my @keys= sort keys %{$self->{XsubAliasValues}->{$value}||{}};
+      # deal with an alias of 0, which might not be in the XsubAlias dataset
+      # yet as 0 is the default for the base function ($fname)
+      push @keys, $fname
+        if $value eq "0" and !defined $self->{XsubAlias}{$fname};
       if (@keys) {
         @keys= map { "'$_'" } map { s/^$self->{Packprefix}//r } @keys;
         WarnHint( $self,
                   "Warning: Aliases '$orig_alias' and "
                   . join(", ", @keys)
-                  . " have identical values",
+                  . " have identical values of $value"
+                  . ( $value eq "0"
+                      ? " - the base function"
+                      : "" ),
                   !$self->{XsubAliasValueClashHinted}++
                   ? "If this is deliberate use a symbolic alias instead."
                   : undef

dist/ExtUtils-ParseXS/t/001-basic.t

@@ -252,12 +252,14 @@ like $stderr, '/No INPUT definition/', "Exercise typemap error";
   $count++ while $content=~/^XS_EUPXS\(XS_My_do\)\n\{/mg;
   is $stderr,
     "Warning: Aliases 'pox' and 'dox', 'lox' have"
-    . " identical values in XSAlias.xs, line 9\n"
+    . " identical values of 1 in XSAlias.xs, line 9\n"
     . "    (If this is deliberate use a symbolic alias instead.)\n"
     . "Warning: Conflicting duplicate alias 'pox' changes"
     . " definition from '1' to '2' in XSAlias.xs, line 10\n"
     . "Warning: Aliases 'docks' and 'dox', 'lox' have"
-    . " identical values in XSAlias.xs, line 11\n",
+    . " identical values of 1 in XSAlias.xs, line 11\n"
+    . "Warning: Aliases 'xunx' and 'do' have identical values"
+    . " of 0 - the base function in XSAlias.xs, line 13\n",
     "Saw expected warnings from XSAlias.xs";
 
   my $expect = quotemeta(<<'EOF_CONTENT');
@@ -273,6 +275,10 @@ like $stderr, '/No INPUT definition/', "Exercise typemap error";
          XSANY.any_i32 = 1;
          cv = newXSproto_portable("My::pox", XS_My_do, file, "$");
          XSANY.any_i32 = 2;
+         cv = newXSproto_portable("My::xukes", XS_My_do, file, "$");
+         XSANY.any_i32 = 0;
+         cv = newXSproto_portable("My::xunx", XS_My_do, file, "$");
+         XSANY.any_i32 = 0;
 EOF_CONTENT
   $expect=~s/(?:\\[ ])+/\\s+/g;
   $expect=qr/$expect/;

dist/ExtUtils-ParseXS/t/XSAlias.xs

@@ -10,6 +10,8 @@ ALIAS:
     pox = 2
     docks = 1
     dachs => lox
+    xunx = 0
+    xukes => do
 CODE:
 {
    int x;