ParseXS: refactor: rm soft_type Node:Param field

The 'soft_type' field was added by me about 13 commits ago to get round
issues where a TYPE/CLASS param's type is being defined both implicitly
(by having the XSUB function name include a class) and explicitly in an
INPUT line.

Further refactoring since then has made the field unnecessary, and so
this commit removed it and just uses the 'type' field of Node::Param
always.

Also add some more tests for dup THIS/CLASS. There were already tests
for a dup in an INPUT line, but not in the signature.

Author: iabyn

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

@@ -956,7 +956,7 @@ EOM
         my ExtUtils::ParseXS::Node::Param $param
             = ExtUtils::ParseXS::Node::Param->new( {
                 var          => $var,
-                soft_type    => $type,
+                type         => $type,
                 is_synthetic => 1,
                 arg_num      => ++$args_count,
               });
@@ -3517,7 +3517,6 @@ sub generate_output {
     my $param = $sig->{names}{$var};
     if ($param) {
       $type = $param->{type};
-      $type = $param->{soft_type} unless defined $type;
     }
   }
 

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

@@ -89,7 +89,6 @@ BEGIN {
     our @FIELDS = (
         @ExtUtils::ParseXS::Node::FIELDS,
         'type',      # The C type of the parameter
-        'soft_type', # The C type be used if not explicitly defined
         'arg_num',   # The arg number (starting at 1) mapped to this param
         'var',       # the name of the parameter
         'default',   # default value (if any)
@@ -124,7 +123,7 @@ sub check {
     my ExtUtils::ParseXS::Node::Param $self = shift;
     my ExtUtils::ParseXS              $pxs  = shift;
 
-    my $type = defined $self->{type} ? $self->{type} : $self->{soft_type};
+    my $type = $self->{type};
 
     # Get the overridden prototype character, if any, associated with the
     # typemap entry for this var's type.
@@ -142,7 +141,7 @@ sub check {
         $pxs->{xsub_sig}{names}{$self->{var}};
 
     if ($sigp) {
-        for (qw(default soft_type)) {
+        for (qw(default)) {
             $self->{$_} = $sigp->{$_} if exists $sigp->{$_};
         }
         if (    defined $sigp->{in_out}
@@ -179,12 +178,10 @@ sub as_code {
     my ExtUtils::ParseXS::Node::Param $self = shift;
     my ExtUtils::ParseXS              $pxs  = shift;
 
-    my ($type, $soft_type, $arg_num, $var, $init, $no_init, $defer, $default)
-        = @{$self}{qw(type soft_type arg_num var init no_init defer default)};
+    my ($type, $arg_num, $var, $init, $no_init, $defer, $default)
+        = @{$self}{qw(type arg_num var init no_init defer default)};
 
     my $arg = $pxs->ST($arg_num, 0);
-
-    $type = $soft_type unless defined $type;
 
     if ($self->{is_length}) {
         # Process length(foo) parameter.

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

@@ -1,7 +1,7 @@
 #!/usr/bin/perl
 
 use strict;
-use Test::More tests => 175;
+use Test::More tests => 179;
 use Config;
 use DynaLoader;
 use ExtUtils::CBuilder;
@@ -1253,6 +1253,28 @@ EOF
                     "dup err" ],
         ],
 
+        [
+            #  don't allow THIS in sig, with type
+            "C++: f6: sig THIS type",
+            [
+                'int',
+                'X::Y::f6(int THIS)',
+            ],
+            [ 1, 0, qr/\QError: duplicate definition of argument 'THIS'/,
+                    "dup err" ],
+        ],
+
+        [
+            #  don't allow THIS in sig, without type
+            "C++: f7: sig THIS no type",
+            [
+                'int',
+                'X::Y::f7(THIS)',
+            ],
+            [ 1, 0, qr/\QError: duplicate definition of argument 'THIS'/,
+                    "dup err" ],
+        ],
+
         [
             # allow CLASS's type to be overridden ...
             "C++: new: override CLASS type",
@@ -1280,6 +1302,28 @@ EOF
                     "dup err" ],
         ],
 
+        [
+            #  don't allow CLASS in sig, with type
+            "C++: new sig CLASS type",
+            [
+                'int',
+                'X::Y::new(int CLASS)',
+            ],
+            [ 1, 0, qr/\QError: duplicate definition of argument 'CLASS'/,
+                    "dup err" ],
+        ],
+
+        [
+            #  don't allow CLASS in sig, without type
+            "C++: new sig CLASS no type",
+            [
+                'int',
+                'X::Y::new(CLASS)',
+            ],
+            [ 1, 0, qr/\QError: duplicate definition of argument 'CLASS'/,
+                    "dup err" ],
+        ],
+
         [
             "C++: DESTROY",
             [