Match pattern matching inside branches

branch-is.diff

diff --git a/src/main/php/lang/ast/syntax/php/IsOperator.class.php b/src/main/php/lang/ast/syntax/php/IsOperator.class.php
index 30832b5..9c3f126 100755
--- a/src/main/php/lang/ast/syntax/php/IsOperator.class.php
+++ b/src/main/php/lang/ast/syntax/php/IsOperator.class.php
@@ -125,6 +125,8 @@ class IsOperator implements Extension {
     });
 
     $language->prefix('match', 0, function($parse, $token) use($pattern) {
+      static $id= 0;
+
       $patterns= null;
       $condition= null;
 
@@ -132,22 +134,9 @@ class IsOperator implements Extension {
         $parse->forward();
         $condition= $this->expression($parse, 0);
         $parse->expecting(')', 'match');
-
-        // See https://wiki.php.net/rfc/pattern-matching#match_is_placement
-        if ('is' === $parse->token->value) {
-          $parse->forward();
-
-          $true= new Literal('true');
-          if ($condition instanceof Variable) {
-            $patterns= $condition;
-            $condition= $true;
-          } else {
-            $patterns= new Variable('Ṁ');
-            $condition= new BinaryExpression(new Braced(new Assignment($patterns, '=', $condition)), '||', $true);
-          }
-        }
       }
 
+      $is= false;
       $default= null;
       $cases= [];
       $parse->expecting('{', 'match');
@@ -156,8 +145,10 @@ class IsOperator implements Extension {
           $parse->forward();
           $parse->expecting('=>', 'match');
           $default= $this->expression($parse, 0);
-        } else if ($patterns) {
-          $match= [new PatternMatch($patterns, $pattern($parse, $this), $parse->token->line)];
+        } else if ('is' === $parse->token->value) {
+          $is= true;
+          $parse->forward();
+          $match= [new PatternMatch(null, $pattern($parse, $this), $parse->token->line)];
           $parse->expecting('=>', 'match');
           $cases[]= new MatchCondition($match, $this->expression($parse, 0), $parse->token->line);
         } else {
@@ -175,6 +166,26 @@ class IsOperator implements Extension {
       }
       $parse->expecting('}', 'match');
 
+      // If one of the branches contains an `is` match, rewrite the statement
+      if ($is) {
+        $patterns= new Variable('Ṁ'.($id++));
+        $condition= new BinaryExpression(
+          new Braced(new Assignment($patterns, '=', $condition)),
+          '||',
+          new Literal('true')
+        );
+
+        foreach ($cases as $case) {
+          foreach ($case->expressions as &$match) {
+            if ($match instanceof PatternMatch) {
+              $match->expression= $patterns;
+            } else {
+              $match= new BinaryExpression($match, '===', $patterns);
+            }
+          }
+        }
+      }
+
       return new MatchExpression($condition, $cases, $default, $token->line);
     });
 
diff --git a/src/test/php/lang/ast/syntax/php/unittest/IsOperatorTest.class.php b/src/test/php/lang/ast/syntax/php/unittest/IsOperatorTest.class.php
index e6b3709..93fb797 100755
--- a/src/test/php/lang/ast/syntax/php/unittest/IsOperatorTest.class.php
+++ b/src/test/php/lang/ast/syntax/php/unittest/IsOperatorTest.class.php
@@ -36,13 +36,14 @@ class IsOperatorTest extends EmittingTest {
     }', $arg));
   }
 
-  #[Test, Values([[1, 'int'], ['test', 'string']])]
+  #[Test, Values([[1, 'int'], ['', 'string'], ['test', 'string'], [null, 'undefined']])]
   public function match_is_variant($arg, $expected) {
     Assert::equals($expected, $this->run('class %T {
-      public function run(string|int $arg) {
-        return match ($arg) is {
-          string => "string",
-          int => "int",
+      public function run(?string|int $arg) {
+        return match ($arg) {
+          is string => "string",
+          is int => "int",
+          null => "undefined",
         };
       }
     }', $arg));
@@ -57,9 +58,9 @@ class IsOperatorTest extends EmittingTest {
           $invoked++;
           return 1;
         };
-        return match ($arg()) is {
-          0 => ["zero", $invoked],
-          1 => ["one", $invoked],
+        return match ($arg()) {
+          is 0 => ["zero", $invoked],
+          is 1 => ["one", $invoked],
         };
       }
     }'));
diff --git a/src/test/php/lang/ast/syntax/php/unittest/VariableBindingTest.class.php b/src/test/php/lang/ast/syntax/php/unittest/VariableBindingTest.class.php
index 3c02f5e..80fcd3d 100755
--- a/src/test/php/lang/ast/syntax/php/unittest/VariableBindingTest.class.php
+++ b/src/test/php/lang/ast/syntax/php/unittest/VariableBindingTest.class.php
@@ -49,8 +49,8 @@ class VariableBindingTest extends EmittingTest {
   public function compound_binding($input) {
     Assert::equals('apple', $this->run('class %T {
       public function run($command) {
-        return match ($command) is {
-          ["get", $object]|["pick", "up", $object]|["pick", $object, "up"] => $object,
+        return match ($command) {
+          is ["get", $object]|["pick", "up", $object]|["pick", $object, "up"] => $object,
           default => null,
         };
       }
@@ -61,8 +61,8 @@ class VariableBindingTest extends EmittingTest {
   public function bind_with_subpattern($input, $expected) {
     Assert::equals($expected, $this->run('class %T {
       public function run($command) {
-        return match ($command) is {
-          ["go", $direction & ("north"|"south"|"east"|"west")] => $direction,
+        return match ($command) {
+          is ["go", $direction & ("north"|"south"|"east"|"west")] => $direction,
           default => null,
         };
       }