diff --git a/lib/scssphp/scssphp/phpcs.xml.dist b/lib/scssphp/scssphp/phpcs.xml.dist
new file mode 100644
index 000000000..b162dbd6b
--- /dev/null
+++ b/lib/scssphp/scssphp/phpcs.xml.dist
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<ruleset name="PSR12 (adapted for PHP 5.6+)">
+    <rule ref="PSR12">
+        <!-- Ignore this PHP 7.1+ sniff as long as we support PHP 5.6+ -->
+        <exclude name="PSR12.Properties.ConstantVisibility.NotFound"/>
+
+        <!-- This sniff doesn't ignore comment blocks -->
+<!--
+        <exclude name="Generic.Files.LineLength"/>
+-->
+    </rule>
+</ruleset>
diff --git a/lib/scssphp/scssphp/src/Block/AtRootBlock.php b/lib/scssphp/scssphp/src/Block/AtRootBlock.php
new file mode 100644
index 000000000..41842c269
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/AtRootBlock.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class AtRootBlock extends Block
+{
+    /**
+     * @var array|null
+     */
+    public $selector;
+
+    /**
+     * @var array|null
+     */
+    public $with;
+
+    public function __construct()
+    {
+        $this->type = Type::T_AT_ROOT;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/CallableBlock.php b/lib/scssphp/scssphp/src/Block/CallableBlock.php
new file mode 100644
index 000000000..a18a87c2a
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/CallableBlock.php
@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Compiler\Environment;
+
+/**
+ * @internal
+ */
+class CallableBlock extends Block
+{
+    /**
+     * @var string
+     */
+    public $name;
+
+    /**
+     * @var array|null
+     */
+    public $args;
+
+    /**
+     * @var Environment|null
+     */
+    public $parentEnv;
+
+    /**
+     * @param string $type
+     */
+    public function __construct($type)
+    {
+        $this->type = $type;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/ContentBlock.php b/lib/scssphp/scssphp/src/Block/ContentBlock.php
new file mode 100644
index 000000000..870849800
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/ContentBlock.php
@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Compiler\Environment;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class ContentBlock extends Block
+{
+    /**
+     * @var array|null
+     */
+    public $child;
+
+    /**
+     * @var Environment|null
+     */
+    public $scope;
+
+    public function __construct()
+    {
+        $this->type = Type::T_INCLUDE;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/DirectiveBlock.php b/lib/scssphp/scssphp/src/Block/DirectiveBlock.php
new file mode 100644
index 000000000..b1d3d1a81
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/DirectiveBlock.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class DirectiveBlock extends Block
+{
+    /**
+     * @var string|array
+     */
+    public $name;
+
+    /**
+     * @var string|array|null
+     */
+    public $value;
+
+    public function __construct()
+    {
+        $this->type = Type::T_DIRECTIVE;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/EachBlock.php b/lib/scssphp/scssphp/src/Block/EachBlock.php
new file mode 100644
index 000000000..b3289579d
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/EachBlock.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class EachBlock extends Block
+{
+    /**
+     * @var string[]
+     */
+    public $vars = [];
+
+    /**
+     * @var array
+     */
+    public $list;
+
+    public function __construct()
+    {
+        $this->type = Type::T_EACH;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/ElseBlock.php b/lib/scssphp/scssphp/src/Block/ElseBlock.php
new file mode 100644
index 000000000..6abb4d775
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/ElseBlock.php
@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class ElseBlock extends Block
+{
+    public function __construct()
+    {
+        $this->type = Type::T_ELSE;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/ElseifBlock.php b/lib/scssphp/scssphp/src/Block/ElseifBlock.php
new file mode 100644
index 000000000..4622bca79
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/ElseifBlock.php
@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class ElseifBlock extends Block
+{
+    /**
+     * @var array
+     */
+    public $cond;
+
+    public function __construct()
+    {
+        $this->type = Type::T_ELSEIF;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/ForBlock.php b/lib/scssphp/scssphp/src/Block/ForBlock.php
new file mode 100644
index 000000000..a9cf6733b
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/ForBlock.php
@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class ForBlock extends Block
+{
+    /**
+     * @var string
+     */
+    public $var;
+
+    /**
+     * @var array
+     */
+    public $start;
+
+    /**
+     * @var array
+     */
+    public $end;
+
+    /**
+     * @var bool
+     */
+    public $until;
+
+    public function __construct()
+    {
+        $this->type = Type::T_FOR;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/IfBlock.php b/lib/scssphp/scssphp/src/Block/IfBlock.php
new file mode 100644
index 000000000..9f21bf88a
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/IfBlock.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class IfBlock extends Block
+{
+    /**
+     * @var array
+     */
+    public $cond;
+
+    /**
+     * @var array<ElseifBlock|ElseBlock>
+     */
+    public $cases = [];
+
+    public function __construct()
+    {
+        $this->type = Type::T_IF;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/MediaBlock.php b/lib/scssphp/scssphp/src/Block/MediaBlock.php
new file mode 100644
index 000000000..c49ee1b2b
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/MediaBlock.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class MediaBlock extends Block
+{
+    /**
+     * @var string|array|null
+     */
+    public $value;
+
+    /**
+     * @var array|null
+     */
+    public $queryList;
+
+    public function __construct()
+    {
+        $this->type = Type::T_MEDIA;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/NestedPropertyBlock.php b/lib/scssphp/scssphp/src/Block/NestedPropertyBlock.php
new file mode 100644
index 000000000..1ea4a6c8a
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/NestedPropertyBlock.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class NestedPropertyBlock extends Block
+{
+    /**
+     * @var bool
+     */
+    public $hasValue;
+
+    /**
+     * @var array
+     */
+    public $prefix;
+
+    public function __construct()
+    {
+        $this->type = Type::T_NESTED_PROPERTY;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Block/WhileBlock.php b/lib/scssphp/scssphp/src/Block/WhileBlock.php
new file mode 100644
index 000000000..ac18d4e02
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Block/WhileBlock.php
@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Block;
+
+use ScssPhp\ScssPhp\Block;
+use ScssPhp\ScssPhp\Type;
+
+/**
+ * @internal
+ */
+class WhileBlock extends Block
+{
+    /**
+     * @var array
+     */
+    public $cond;
+
+    public function __construct()
+    {
+        $this->type = Type::T_WHILE;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/CompilationResult.php b/lib/scssphp/scssphp/src/CompilationResult.php
new file mode 100644
index 000000000..36adb0da4
--- /dev/null
+++ b/lib/scssphp/scssphp/src/CompilationResult.php
@@ -0,0 +1,69 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp;
+
+class CompilationResult
+{
+    /**
+     * @var string
+     */
+    private $css;
+
+    /**
+     * @var string|null
+     */
+    private $sourceMap;
+
+    /**
+     * @var string[]
+     */
+    private $includedFiles;
+
+    /**
+     * @param string $css
+     * @param string|null $sourceMap
+     * @param string[] $includedFiles
+     */
+    public function __construct($css, $sourceMap, array $includedFiles)
+    {
+        $this->css = $css;
+        $this->sourceMap = $sourceMap;
+        $this->includedFiles = $includedFiles;
+    }
+
+    /**
+     * @return string
+     */
+    public function getCss()
+    {
+        return $this->css;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getIncludedFiles()
+    {
+        return $this->includedFiles;
+    }
+
+    /**
+     * The sourceMap content, if it was generated
+     *
+     * @return null|string
+     */
+    public function getSourceMap()
+    {
+        return $this->sourceMap;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Compiler/CachedResult.php b/lib/scssphp/scssphp/src/Compiler/CachedResult.php
new file mode 100644
index 000000000..a66291996
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Compiler/CachedResult.php
@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Compiler;
+
+use ScssPhp\ScssPhp\CompilationResult;
+
+/**
+ * @internal
+ */
+class CachedResult
+{
+    /**
+     * @var CompilationResult
+     */
+    private $result;
+
+    /**
+     * @var array<string, int>
+     */
+    private $parsedFiles;
+
+    /**
+     * @var array
+     * @phpstan-var list<array{currentDir: string|null, path: string, filePath: string}>
+     */
+    private $resolvedImports;
+
+    /**
+     * @param CompilationResult  $result
+     * @param array<string, int> $parsedFiles
+     * @param array              $resolvedImports
+     *
+     * @phpstan-param list<array{currentDir: string|null, path: string, filePath: string}> $resolvedImports
+     */
+    public function __construct(CompilationResult $result, array $parsedFiles, array $resolvedImports)
+    {
+        $this->result = $result;
+        $this->parsedFiles = $parsedFiles;
+        $this->resolvedImports = $resolvedImports;
+    }
+
+    /**
+     * @return CompilationResult
+     */
+    public function getResult()
+    {
+        return $this->result;
+    }
+
+    /**
+     * @return array<string, int>
+     */
+    public function getParsedFiles()
+    {
+        return $this->parsedFiles;
+    }
+
+    /**
+     * @return array
+     *
+     * @phpstan-return list<array{currentDir: string|null, path: string, filePath: string}>
+     */
+    public function getResolvedImports()
+    {
+        return $this->resolvedImports;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Exception/SassException.php b/lib/scssphp/scssphp/src/Exception/SassException.php
new file mode 100644
index 000000000..9f62b3cd2
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Exception/SassException.php
@@ -0,0 +1,7 @@
+<?php
+
+namespace ScssPhp\ScssPhp\Exception;
+
+interface SassException
+{
+}
diff --git a/lib/scssphp/scssphp/src/Exception/SassScriptException.php b/lib/scssphp/scssphp/src/Exception/SassScriptException.php
new file mode 100644
index 000000000..19356a7a1
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Exception/SassScriptException.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace ScssPhp\ScssPhp\Exception;
+
+/**
+ * An exception thrown by SassScript.
+ *
+ * This class does not implement SassException on purpose, as it should
+ * never be returned to the outside code. The compilation will catch it
+ * and replace it with a SassException reporting the location of the
+ * error.
+ */
+class SassScriptException extends \Exception
+{
+    /**
+     * Creates a SassScriptException with support for an argument name.
+     *
+     * This helper ensures a consistent handling of argument names in the
+     * error message, without duplicating it.
+     *
+     * @param string      $message
+     * @param string|null $name    The argument name, without $
+     *
+     * @return SassScriptException
+     */
+    public static function forArgument($message, $name = null)
+    {
+        $varDisplay = !\is_null($name) ? "\${$name}: " : '';
+
+        return new self($varDisplay . $message);
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Logger/LoggerInterface.php b/lib/scssphp/scssphp/src/Logger/LoggerInterface.php
new file mode 100644
index 000000000..7c0a2f76e
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Logger/LoggerInterface.php
@@ -0,0 +1,48 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Logger;
+
+/**
+ * Interface implemented by loggers for warnings and debug messages.
+ *
+ * The official Sass implementation recommends that loggers report the
+ * messages immediately rather than waiting for the end of the
+ * compilation, to provide a better debugging experience when the
+ * compilation does not end (error or infinite loop after the warning
+ * for instance).
+ */
+interface LoggerInterface
+{
+    /**
+     * Emits a warning with the given message.
+     *
+     * If $deprecation is true, it indicates that this is a deprecation
+     * warning. Implementations should surface all this information to
+     * the end user.
+     *
+     * @param string $message
+     * @param bool  $deprecation
+     *
+     * @return void
+     */
+    public function warn($message, $deprecation = false);
+
+    /**
+     * Emits a debugging message.
+     *
+     * @param string $message
+     *
+     * @return void
+     */
+    public function debug($message);
+}
diff --git a/lib/scssphp/scssphp/src/Logger/QuietLogger.php b/lib/scssphp/scssphp/src/Logger/QuietLogger.php
new file mode 100644
index 000000000..ad7c07537
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Logger/QuietLogger.php
@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Logger;
+
+/**
+ * A logger that silently ignores all messages.
+ *
+ * @final
+ */
+class QuietLogger implements LoggerInterface
+{
+    public function warn($message, $deprecation = false)
+    {
+    }
+
+    public function debug($message)
+    {
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Logger/StreamLogger.php b/lib/scssphp/scssphp/src/Logger/StreamLogger.php
new file mode 100644
index 000000000..7db7cc189
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Logger/StreamLogger.php
@@ -0,0 +1,62 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp\Logger;
+
+/**
+ * A logger that prints to a PHP stream (for instance stderr)
+ *
+ * @final
+ */
+class StreamLogger implements LoggerInterface
+{
+    private $stream;
+    private $closeOnDestruct;
+
+    /**
+     * @param resource $stream          A stream resource
+     * @param bool     $closeOnDestruct If true, takes ownership of the stream and close it on destruct to avoid leaks.
+     */
+    public function __construct($stream, $closeOnDestruct = false)
+    {
+        $this->stream = $stream;
+        $this->closeOnDestruct = $closeOnDestruct;
+    }
+
+    /**
+     * @internal
+     */
+    public function __destruct()
+    {
+        if ($this->closeOnDestruct) {
+            fclose($this->stream);
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function warn($message, $deprecation = false)
+    {
+        $prefix = ($deprecation ? 'DEPRECATION ' : '') . 'WARNING: ';
+
+        fwrite($this->stream, $prefix . $message . "\n\n");
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function debug($message)
+    {
+        fwrite($this->stream, $message . "\n");
+    }
+}
diff --git a/lib/scssphp/scssphp/src/OutputStyle.php b/lib/scssphp/scssphp/src/OutputStyle.php
new file mode 100644
index 000000000..c284639c1
--- /dev/null
+++ b/lib/scssphp/scssphp/src/OutputStyle.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace ScssPhp\ScssPhp;
+
+final class OutputStyle
+{
+    const EXPANDED = 'expanded';
+    const COMPRESSED = 'compressed';
+}
diff --git a/lib/scssphp/scssphp/src/Util/Path.php b/lib/scssphp/scssphp/src/Util/Path.php
new file mode 100644
index 000000000..f399e41ab
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Util/Path.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace ScssPhp\ScssPhp\Util;
+
+/**
+ * @internal
+ */
+class Path
+{
+    /**
+     * @param string $path
+     *
+     * @return bool
+     */
+    public static function isAbsolute($path)
+    {
+        if ($path === '') {
+            return false;
+        }
+
+        if ($path[0] === '/') {
+            return true;
+        }
+
+        if (\DIRECTORY_SEPARATOR !== '\\') {
+            return false;
+        }
+
+        if ($path[0] === '\\') {
+            return true;
+        }
+
+        if (\strlen($path) < 3) {
+            return false;
+        }
+
+        if ($path[1] !== ':') {
+            return false;
+        }
+
+        if ($path[2] !== '/' && $path[2] !== '\\') {
+            return false;
+        }
+
+        if (!preg_match('/^[A-Za-z]$/', $path[0])) {
+            return false;
+        }
+
+        return true;
+    }
+
+    /**
+     * @param string $part1
+     * @param string $part2
+     *
+     * @return string
+     */
+    public static function join($part1, $part2)
+    {
+        if ($part1 === '' || self::isAbsolute($part2)) {
+            return $part2;
+        }
+
+        if ($part2 === '') {
+            return $part1;
+        }
+
+        $last = $part1[\strlen($part1) - 1];
+        $separator = \DIRECTORY_SEPARATOR;
+
+        if ($last === '/' || $last === \DIRECTORY_SEPARATOR) {
+            $separator = '';
+        }
+
+        return $part1 . $separator . $part2;
+    }
+}
diff --git a/lib/scssphp/scssphp/src/ValueConverter.php b/lib/scssphp/scssphp/src/ValueConverter.php
new file mode 100644
index 000000000..e12a0eb54
--- /dev/null
+++ b/lib/scssphp/scssphp/src/ValueConverter.php
@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp;
+
+use ScssPhp\ScssPhp\Node\Number;
+
+final class ValueConverter
+{
+    // Prevent instantiating it
+    private function __construct()
+    {
+    }
+
+    /**
+     * Parses a value from a Scss source string.
+     *
+     * The returned value is guaranteed to be supported by the
+     * Compiler methods for registering custom variables. No other
+     * guarantee about it is provided. It should be considered
+     * opaque values by the caller.
+     *
+     * @param string $source
+     *
+     * @return mixed
+     */
+    public static function parseValue($source)
+    {
+        $parser = new Parser(__CLASS__);
+
+        if (!$parser->parseValue($source, $value)) {
+            throw new \InvalidArgumentException(sprintf('Invalid value source "%s".', $source));
+        }
+
+        return $value;
+    }
+
+    /**
+     * Converts a PHP value to a Sass value
+     *
+     * The returned value is guaranteed to be supported by the
+     * Compiler methods for registering custom variables. No other
+     * guarantee about it is provided. It should be considered
+     * opaque values by the caller.
+     *
+     * @param mixed $value
+     *
+     * @return mixed
+     */
+    public static function fromPhp($value)
+    {
+        if ($value instanceof Number) {
+            return $value;
+        }
+
+        if (is_array($value) && isset($value[0]) && \in_array($value[0], [Type::T_NULL, Type::T_COLOR, Type::T_KEYWORD, Type::T_LIST, Type::T_MAP, Type::T_STRING])) {
+            return $value;
+        }
+
+        if ($value === null) {
+            return Compiler::$null;
+        }
+
+        if ($value === true) {
+            return Compiler::$true;
+        }
+
+        if ($value === false) {
+            return Compiler::$false;
+        }
+
+        if ($value === '') {
+            return Compiler::$emptyString;
+        }
+
+        if (\is_int($value) || \is_float($value)) {
+            return new Number($value, '');
+        }
+
+        if (\is_string($value)) {
+            return [Type::T_STRING, '"', [$value]];
+        }
+
+        throw new \InvalidArgumentException(sprintf('Cannot convert the value of type "%s" to a Sass value.', gettype($value)));
+    }
+}
diff --git a/lib/scssphp/scssphp/src/Warn.php b/lib/scssphp/scssphp/src/Warn.php
new file mode 100644
index 000000000..592b44c70
--- /dev/null
+++ b/lib/scssphp/scssphp/src/Warn.php
@@ -0,0 +1,84 @@
+<?php
+
+/**
+ * SCSSPHP
+ *
+ * @copyright 2012-2020 Leaf Corcoran
+ *
+ * @license http://opensource.org/licenses/MIT MIT
+ *
+ * @link http://scssphp.github.io/scssphp
+ */
+
+namespace ScssPhp\ScssPhp;
+
+final class Warn
+{
+    /**
+     * @var callable|null
+     * @phpstan-var (callable(string, bool): void)|null
+     */
+    private static $callback;
+
+    /**
+     * Prints a warning message associated with the current `@import` or function call.
+     *
+     * This may only be called within a custom function or importer callback.
+     *
+     * @param string $message
+     *
+     * @return void
+     */
+    public static function warning($message)
+    {
+        self::reportWarning($message, false);
+    }
+
+    /**
+     * Prints a deprecation warning message associated with the current `@import` or function call.
+     *
+     * This may only be called within a custom function or importer callback.
+     *
+     * @param string $message
+     *
+     * @return void
+     */
+    public static function deprecation($message)
+    {
+        self::reportWarning($message, true);
+    }
+
+    /**
+     * @param callable|null $callback
+     *
+     * @return callable|null The previous warn callback
+     *
+     * @phpstan-param (callable(string, bool): void)|null $callback
+     *
+     * @phpstan-return (callable(string, bool): void)|null
+     *
+     * @internal
+     */
+    public static function setCallback(callable $callback = null)
+    {
+        $previousCallback = self::$callback;
+        self::$callback = $callback;
+
+        return $previousCallback;
+    }
+
+    /**
+     * @param string $message
+     * @param bool   $deprecation
+     *
+     * @return void
+     */
+    private static function reportWarning($message, $deprecation)
+    {
+        if (self::$callback === null) {
+            throw new \BadMethodCallException('The warning Reporter may only be called within a custom function or importer callback.');
+        }
+
+        \call_user_func(self::$callback, $message, $deprecation);
+    }
+}