Avoid PHP warnings for break & continue

Our previous mechanism of doing a "lookbehind" with twig
lead to array key warnings. Instead we now look ahead, which
is also valid from the perspective of twig, to determine if
more loops are ending than closing, and for break if enough
loops are ending to break out of.

Author: iquito

composer.json

@@ -47,7 +47,7 @@
         "psalm_base": "vendor/bin/psalm --set-baseline=psalm-baseline.xml",
         "phpunit": "vendor/bin/phpunit --colors=always",
         "phpunit_clover": "vendor/bin/phpunit --coverage-text --coverage-clover build/logs/clover.xml",
-        "coverage": "vendor/bin/phpunit --coverage-html tests/_reports",
+        "coverage": "XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-html tests/_reports",
         "phpcs": "vendor/bin/phpcs --standard=ruleset.xml --extensions=php --cache=.phpcs-cache --colors src tests",
         "phpcsfix": "vendor/bin/phpcbf --standard=ruleset.xml --extensions=php --cache=.phpcs-cache src tests",
         "binupdate": "@composer bin all update --ansi",

src/TokenParser/BreakOrContinueTokenParser.php

@@ -33,40 +33,37 @@ public function parse(Token $token): Node
 
         $stream->expect(Token::BLOCK_END_TYPE);
 
-        // Trick to check if we are currently in a loop.
-        $currentForLoop = 0;
+        // Count how many loops are starting minus the loops ending
+        $loopCount = 0;
 
         for ($i = 1; true; $i++) {
-            // If we look back too far in the stream twig will throw a SyntaxError
-            // and there we often get another error because an illegal offset is accessed
-            // when creating the SyntaxError, so we catch all throwables to be safe
             try {
-                // We look back by using a negative integer, which is not intended by twig and seems
-                // a bit hacky, but does work for our purposes currently and gives us the opportunity
-                // to detect illegal usages of break/continue outside of loops or in not-enough-nested contexts
-                $token = $stream->look(-$i);
-            } catch (\Throwable $e) {
+                // Look ahead to find for and endfor tokens to make sure
+                // there are more loops ending than starting
+                $token = $stream->look($i);
+            } catch (SyntaxError $e) {
+                // End of template, leading to SyntaxError
                 break;
             }
 
             // Count both "for" loops and "foreach" loops
             if ($token->test(Token::NAME_TYPE, 'for') || $token->test(Token::NAME_TYPE, 'foreach')) {
-                $currentForLoop++;
+                $loopCount++;
             } elseif ($token->test(Token::NAME_TYPE, 'endfor') || $token->test(Token::NAME_TYPE, 'endforeach')) {
-                $currentForLoop--;
+                $loopCount--;
             }
         }
 
-
-        if ($currentForLoop < 1) {
+        // There should be more loops ending than starting, making loopCount negative
+        if ($loopCount >= 0) {
             throw new SyntaxError(
                 \ucfirst($this->getTag()) . ' tag is only allowed in \'for\' or \'foreach\' loops.',
                 $stream->getCurrent()->getLine(),
                 $stream->getSourceContext()
             );
-        } elseif ($currentForLoop < $loopNumber) {
+        } elseif (\abs($loopCount) < $loopNumber) {
             throw new SyntaxError(
-                \ucfirst($this->getTag()) . ' tag uses a loop number higher than the actual loops in this context - you are using the number ' . $loopNumber . ' but in the given context the maximum number is ' . $currentForLoop . '.',
+                \ucfirst($this->getTag()) . ' tag uses a loop number higher than the actual loops in this context - you are using the number ' . $loopNumber . ' but in the given context the maximum number is ' . \abs($loopCount) . '.',
                 $stream->getCurrent()->getLine(),
                 $stream->getSourceContext()
             );