Remove more ancient stuff

Author: oliverklee

src/Parsing/ParserState.php

@@ -150,13 +150,6 @@ public function parseIdentifier($ignoreCase = true)
     public function parseCharacter($isForIdentifier)
     {
         if ($this->peek() === '\\') {
-            if (
-                $isForIdentifier && $this->parserSettings->usesLenientParsing()
-                && ($this->comes('\\0') || $this->comes('\\9'))
-            ) {
-                // Non-strings can contain \0 or \9 which is an IE hack supported in lenient parsing.
-                return null;
-            }
             $this->consume('\\');
             if ($this->comes('\\n') || $this->comes('\\r')) {
                 return '';

src/Value/Value.php

@@ -50,7 +50,6 @@ public static function parseValue(ParserState $parserState, array $aListDelimite
         while (
         !($parserState->comes('}') || $parserState->comes(';') || $parserState->comes('!')
             || $parserState->comes(')')
-            || $parserState->comes('\\')
             || $parserState->isEnd())
         ) {
             if (\count($aStack) > 0) {

tests/ParserTest.php

@@ -1036,28 +1036,6 @@ public function unexpectedTokenExceptionLineNo(): void
         }
     }
 
-    /**
-     * @test
-     */
-    public function ieHacksCauseExceptionInStrictMode(): void
-    {
-        $this->expectException(UnexpectedTokenException::class);
-
-        self::parsedStructureForFile('ie-hacks', Settings::create()->beStrict());
-    }
-
-    /**
-     * @test
-     */
-    public function ieHacksArePartiallyRemovedInLenientMode(): void
-    {
-        $document = self::parsedStructureForFile('ie-hacks', Settings::create()->withLenientParsing(true));
-
-        $expected = 'p {padding-right: .75rem;background-image: none;color: red;'
-            . 'background-color: red;background-color: red;content: "red 	\\0";content: "red઼";}';
-        self::assertSame($expected, $document->render());
-    }
-
     /**
      * @depends files
      *