minor #43778 Use try/finally to restore error handlers (derrabus)

This PR was merged into the 5.4 branch.

Discussion
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Use try/finally to restore error handlers

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | N/A
| License       | MIT
| Doc PR        | N/A

This PR attempts to make some code dealing with temporary error handlers a bit more robust by making sure the old error handler is always restored. A forgotten error handler is pretty hard to debug, so I'd like our code to be a it more defensive here.

Commits
-------

057716c6a2 Use try/finally to restore error handlers

Author: derrabus

Matcher/Dumper/StaticPrefixCollection.php

@@ -151,40 +151,43 @@ private function getCommonPrefix(string $prefix, string $anotherPrefix): array
         $staticLength = null;
         set_error_handler([__CLASS__, 'handleError']);
 
-        for ($i = $baseLength; $i < $end && $prefix[$i] === $anotherPrefix[$i]; ++$i) {
-            if ('(' === $prefix[$i]) {
-                $staticLength = $staticLength ?? $i;
-                for ($j = 1 + $i, $n = 1; $j < $end && 0 < $n; ++$j) {
-                    if ($prefix[$j] !== $anotherPrefix[$j]) {
-                        break 2;
+        try {
+            for ($i = $baseLength; $i < $end && $prefix[$i] === $anotherPrefix[$i]; ++$i) {
+                if ('(' === $prefix[$i]) {
+                    $staticLength = $staticLength ?? $i;
+                    for ($j = 1 + $i, $n = 1; $j < $end && 0 < $n; ++$j) {
+                        if ($prefix[$j] !== $anotherPrefix[$j]) {
+                            break 2;
+                        }
+                        if ('(' === $prefix[$j]) {
+                            ++$n;
+                        } elseif (')' === $prefix[$j]) {
+                            --$n;
+                        } elseif ('\\' === $prefix[$j] && (++$j === $end || $prefix[$j] !== $anotherPrefix[$j])) {
+                            --$j;
+                            break;
+                        }
                     }
-                    if ('(' === $prefix[$j]) {
-                        ++$n;
-                    } elseif (')' === $prefix[$j]) {
-                        --$n;
-                    } elseif ('\\' === $prefix[$j] && (++$j === $end || $prefix[$j] !== $anotherPrefix[$j])) {
-                        --$j;
+                    if (0 < $n) {
                         break;
                     }
-                }
-                if (0 < $n) {
-                    break;
-                }
-                if (('?' === ($prefix[$j] ?? '') || '?' === ($anotherPrefix[$j] ?? '')) && ($prefix[$j] ?? '') !== ($anotherPrefix[$j] ?? '')) {
-                    break;
-                }
-                $subPattern = substr($prefix, $i, $j - $i);
-                if ($prefix !== $anotherPrefix && !preg_match('/^\(\[[^\]]++\]\+\+\)$/', $subPattern) && !preg_match('{(?<!'.$subPattern.')}', '')) {
-                    // sub-patterns of variable length are not considered as common prefixes because their greediness would break in-order matching
+                    if (('?' === ($prefix[$j] ?? '') || '?' === ($anotherPrefix[$j] ?? '')) && ($prefix[$j] ?? '') !== ($anotherPrefix[$j] ?? '')) {
+                        break;
+                    }
+                    $subPattern = substr($prefix, $i, $j - $i);
+                    if ($prefix !== $anotherPrefix && !preg_match('/^\(\[[^\]]++\]\+\+\)$/', $subPattern) && !preg_match('{(?<!'.$subPattern.')}', '')) {
+                        // sub-patterns of variable length are not considered as common prefixes because their greediness would break in-order matching
+                        break;
+                    }
+                    $i = $j - 1;
+                } elseif ('\\' === $prefix[$i] && (++$i === $end || $prefix[$i] !== $anotherPrefix[$i])) {
+                    --$i;
                     break;
                 }
-                $i = $j - 1;
-            } elseif ('\\' === $prefix[$i] && (++$i === $end || $prefix[$i] !== $anotherPrefix[$i])) {
-                --$i;
-                break;
             }
+        } finally {
+            restore_error_handler();
         }
-        restore_error_handler();
         if ($i < $end && 0b10 === (\ord($prefix[$i]) >> 6) && preg_match('//u', $prefix.' '.$anotherPrefix)) {
             do {
                 // Prevent cutting in the middle of an UTF-8 characters