Fix warnings and php 7.4 deprications

Author: exussum12

src/ArgParser.php

@@ -28,7 +28,7 @@ public function getArg(string $name): string
     protected function numericArg(int $position): string
     {
         foreach ($this->args as $arg) {
-            if ($arg{0} != '-' && $position-- == 0) {
+            if ($arg[0] != '-' && $position-- == 0) {
                 return $arg;
             }
         }
@@ -42,7 +42,7 @@ protected function letterArg($name): string
         foreach ($this->args as $arg) {
             list($value, $arg) = $this->splitArg($arg);
 
-            if ($arg{0} == '-' && $name == $arg) {
+            if ($arg[0] == '-' && $name == $arg) {
                 return $value;
             }
         }

src/Loaders/PhpCs.php

@@ -121,7 +121,9 @@ protected function addInvalidLine(string $file, stdClass $message)
 
         $line = $message->line;
 
-        if ($error = $this->messageStartsWith($message->source, $this->lookupErrorPrefix)) {
+        $error = $this->messageStartsWith($message->source, $this->lookupErrorPrefix);
+
+        if ($error) {
             $this->handleLookupError($file, $message, $error);
             return;
         }

src/Loaders/PhpStan.php

@@ -41,7 +41,9 @@ public function parseLines(): array
         $lineNumber = 0;
         while (($line = fgets($this->file)) !== false) {
             $filename = $this->checkForFilename($line, $filename);
-            if ($lineNumber = $this->getLineNumber($line, $lineNumber)) {
+            $lineNumber = $this->getLineNumber($line, $lineNumber);
+
+            if ($lineNumber) {
                 $error = $this->getMessage($line);
                 if ($this->isExtendedMessage($line)) {
                     $this->appendError($filename, $lineNumber, $error);

src/PhpunitFilter.php

@@ -26,7 +26,8 @@ public function getTestsForRunning($fuzziness = 0)
         $runTests = [];
         foreach ($changes as $file => $lines) {
             try {
-                if ($found = $this->matcher->match($file, $fileNames)) {
+                $found = $this->matcher->match($file, $fileNames);
+                if ($found) {
                     foreach ($lines as $line) {
                         $runTests = $this->matchFuzzyLines($fuzziness, $testData, $found, $line, $runTests);
                     }