From f9532231d2ba124713620a28ac39bd512d75c99e Mon Sep 17 00:00:00 2001
From: Adrien Crivelli <adrien.crivelli@gmail.com>
Date: Sun, 4 Apr 2021 22:20:00 +0900
Subject: [PATCH] PHPStan Level 3

---
 phpstan.neon.dist                             |  4 +-
 .../Calculation/Calculation.php               |  4 +-
 .../Calculation/Database/DatabaseAbstract.php |  2 +-
 .../Calculation/Engineering.php               |  4 +-
 .../Calculation/Engineering/ConvertBinary.php |  2 +-
 .../Calculation/Engineering/ConvertHex.php    |  4 +-
 .../Calculation/Engineering/ConvertOctal.php  |  4 +-
 .../Calculation/Engineering/ConvertUOM.php    |  4 +-
 .../Calculation/FormulaParser.php             |  4 +-
 src/PhpSpreadsheet/Calculation/Functions.php  |  2 +-
 .../Calculation/LookupRef/Offset.php          |  2 +-
 .../Calculation/MathTrig/Fact.php             |  2 +-
 .../Calculation/Statistical.php               |  4 +-
 .../Calculation/Statistical/Trends.php        |  4 +-
 src/PhpSpreadsheet/Cell/Cell.php              |  5 +-
 src/PhpSpreadsheet/Chart/Axis.php             | 16 ++---
 src/PhpSpreadsheet/Chart/DataSeries.php       | 20 +++---
 src/PhpSpreadsheet/Chart/DataSeriesValues.php |  4 +-
 src/PhpSpreadsheet/Chart/PlotArea.php         |  2 +-
 src/PhpSpreadsheet/Collection/Cells.php       |  6 +-
 src/PhpSpreadsheet/Document/Properties.php    |  2 +-
 src/PhpSpreadsheet/HashTable.php              |  4 +-
 src/PhpSpreadsheet/Reader/BaseReader.php      |  2 +-
 src/PhpSpreadsheet/Reader/Xls.php             |  6 +-
 src/PhpSpreadsheet/Reader/Xlsx.php            |  5 +-
 src/PhpSpreadsheet/Reader/Xlsx/Theme.php      | 12 ++--
 src/PhpSpreadsheet/Settings.php               |  2 +-
 src/PhpSpreadsheet/Shared/Date.php            |  2 +-
 src/PhpSpreadsheet/Shared/Drawing.php         |  6 +-
 src/PhpSpreadsheet/Shared/Font.php            |  2 +-
 .../Shared/JAMA/LUDecomposition.php           |  2 +-
 src/PhpSpreadsheet/Shared/JAMA/Matrix.php     |  8 +--
 .../Shared/OLE/ChainedBlockStream.php         |  4 +-
 src/PhpSpreadsheet/Shared/OLERead.php         |  2 +-
 src/PhpSpreadsheet/Shared/Trend/BestFit.php   | 23 +++----
 .../Shared/Trend/PolynomialBestFit.php        |  5 +-
 src/PhpSpreadsheet/Shared/Xls.php             | 10 +--
 src/PhpSpreadsheet/Spreadsheet.php            | 25 ++++----
 src/PhpSpreadsheet/Style/Alignment.php        | 12 ++--
 src/PhpSpreadsheet/Style/Border.php           |  2 +-
 src/PhpSpreadsheet/Style/Fill.php             |  8 +--
 src/PhpSpreadsheet/Style/Font.php             | 34 +++++-----
 src/PhpSpreadsheet/Style/NumberFormat.php     |  8 +--
 src/PhpSpreadsheet/Worksheet/AutoFilter.php   |  8 +--
 .../Worksheet/AutoFilter/Column.php           | 10 +--
 .../Worksheet/AutoFilter/Column/Rule.php      |  4 +-
 src/PhpSpreadsheet/Worksheet/BaseDrawing.php  | 12 ++--
 src/PhpSpreadsheet/Worksheet/CellIterator.php |  1 +
 src/PhpSpreadsheet/Worksheet/Column.php       |  1 +
 .../Worksheet/ColumnCellIterator.php          |  2 +-
 .../Worksheet/ColumnIterator.php              |  1 +
 .../Worksheet/Drawing/Shadow.php              |  6 +-
 src/PhpSpreadsheet/Worksheet/Iterator.php     |  8 ---
 .../Worksheet/MemoryDrawing.php               |  1 -
 src/PhpSpreadsheet/Worksheet/PageSetup.php    |  2 +-
 src/PhpSpreadsheet/Worksheet/Row.php          |  1 +
 src/PhpSpreadsheet/Worksheet/RowIterator.php  |  8 ---
 src/PhpSpreadsheet/Worksheet/Worksheet.php    | 34 +++++-----
 src/PhpSpreadsheet/Writer/Html.php            |  4 +-
 src/PhpSpreadsheet/Writer/Pdf.php             |  2 +-
 src/PhpSpreadsheet/Writer/Xls.php             |  6 +-
 src/PhpSpreadsheet/Writer/Xls/BIFFwriter.php  |  2 +-
 src/PhpSpreadsheet/Writer/Xls/Font.php        |  2 +-
 src/PhpSpreadsheet/Writer/Xls/Worksheet.php   | 63 +++++--------------
 src/PhpSpreadsheet/Writer/Xls/Xf.php          |  8 +--
 src/PhpSpreadsheet/Writer/Xlsx.php            |  7 +++
 src/PhpSpreadsheet/Writer/Xlsx/DocProps.php   |  4 +-
 src/PhpSpreadsheet/Writer/Xlsx/Theme.php      |  6 +-
 .../Functions/Engineering/ImConjugateTest.php |  5 --
 .../Functions/Engineering/ImCosTest.php       |  5 --
 .../Functions/Engineering/ImCoshTest.php      |  5 --
 .../Functions/Engineering/ImCotTest.php       |  5 --
 .../Functions/Engineering/ImCscTest.php       |  5 --
 .../Functions/Engineering/ImCschTest.php      |  5 --
 .../Functions/Engineering/ImDivTest.php       |  5 --
 .../Functions/Engineering/ImExpTest.php       |  5 --
 .../Functions/Engineering/ImLnTest.php        |  5 --
 .../Functions/Engineering/ImLog10Test.php     |  5 --
 .../Functions/Engineering/ImLog2Test.php      |  5 --
 .../Functions/Engineering/ImPowerTest.php     |  5 --
 .../Functions/Engineering/ImProductTest.php   |  5 --
 .../Functions/Engineering/ImSecTest.php       |  5 --
 .../Functions/Engineering/ImSechTest.php      |  5 --
 .../Functions/Engineering/ImSinTest.php       |  5 --
 .../Functions/Engineering/ImSinhTest.php      |  5 --
 .../Functions/Engineering/ImSqrtTest.php      |  5 --
 .../Functions/Engineering/ImSubTest.php       |  5 --
 .../Functions/Engineering/ImSumTest.php       |  5 --
 .../Functions/Engineering/ImTanTest.php       |  5 --
 tests/PhpSpreadsheetTests/SettingsTest.php    |  2 +-
 90 files changed, 225 insertions(+), 370 deletions(-)

diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 53bbb0e6..6917c78c 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,8 +1,10 @@
 parameters:
-    level: 2
+    level: 3
     paths:
         - src/
         - tests/
+    parallel:
+        processTimeout: 300.0
     ignoreErrors:
         - '~^Class GdImage not found\.$~'
         - '~^Return typehint of method .* has invalid type GdImage\.$~'
diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index 9477131f..a11b8a12 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -5234,10 +5234,8 @@ class Calculation
 
     /**
      * Get a list of all implemented functions as an array of function objects.
-     *
-     * @return array of Category
      */
-    public function getFunctions()
+    public function getFunctions(): array
     {
         return self::$phpSpreadsheetFunctions;
     }
diff --git a/src/PhpSpreadsheet/Calculation/Database/DatabaseAbstract.php b/src/PhpSpreadsheet/Calculation/Database/DatabaseAbstract.php
index cf48bd88..2c9bb2de 100644
--- a/src/PhpSpreadsheet/Calculation/Database/DatabaseAbstract.php
+++ b/src/PhpSpreadsheet/Calculation/Database/DatabaseAbstract.php
@@ -57,7 +57,7 @@ abstract class DatabaseAbstract
      *                                        the column label in which you specify a condition for the
      *                                        column.
      *
-     * @return array of mixed
+     * @return mixed[]
      */
     protected static function filter(array $database, array $criteria): array
     {
diff --git a/src/PhpSpreadsheet/Calculation/Engineering.php b/src/PhpSpreadsheet/Calculation/Engineering.php
index 7584556a..a70ddac5 100644
--- a/src/PhpSpreadsheet/Calculation/Engineering.php
+++ b/src/PhpSpreadsheet/Calculation/Engineering.php
@@ -1395,7 +1395,7 @@ class Engineering
      *
      * @see Use the getConversionMultipliers() method in the ConvertUOM class instead
      *
-     * @return array of mixed
+     * @return mixed[]
      */
     public static function getConversionMultipliers()
     {
@@ -1412,7 +1412,7 @@ class Engineering
      *
      * @see Use the getBinaryConversionMultipliers() method in the ConvertUOM class instead
      *
-     * @return array of mixed
+     * @return mixed[]
      */
     public static function getBinaryConversionMultipliers()
     {
diff --git a/src/PhpSpreadsheet/Calculation/Engineering/ConvertBinary.php b/src/PhpSpreadsheet/Calculation/Engineering/ConvertBinary.php
index ff4873ac..a662b78d 100644
--- a/src/PhpSpreadsheet/Calculation/Engineering/ConvertBinary.php
+++ b/src/PhpSpreadsheet/Calculation/Engineering/ConvertBinary.php
@@ -38,7 +38,7 @@ class ConvertBinary extends ConvertBase
             return '-' . (512 - bindec($value));
         }
 
-        return bindec($value);
+        return (string) bindec($value);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Calculation/Engineering/ConvertHex.php b/src/PhpSpreadsheet/Calculation/Engineering/ConvertHex.php
index cbf155ed..de1b0704 100644
--- a/src/PhpSpreadsheet/Calculation/Engineering/ConvertHex.php
+++ b/src/PhpSpreadsheet/Calculation/Engineering/ConvertHex.php
@@ -85,10 +85,10 @@ class ConvertHex extends ConvertBase
                 $binX[$i] = ($binX[$i] == '1' ? '0' : '1');
             }
 
-            return (bindec($binX) + 1) * -1;
+            return (string) ((bindec($binX) + 1) * -1);
         }
 
-        return bindec($binX);
+        return (string) bindec($binX);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Calculation/Engineering/ConvertOctal.php b/src/PhpSpreadsheet/Calculation/Engineering/ConvertOctal.php
index 872f0b70..1181e2ee 100644
--- a/src/PhpSpreadsheet/Calculation/Engineering/ConvertOctal.php
+++ b/src/PhpSpreadsheet/Calculation/Engineering/ConvertOctal.php
@@ -85,10 +85,10 @@ class ConvertOctal extends ConvertBase
                 $binX[$i] = ($binX[$i] == '1' ? '0' : '1');
             }
 
-            return (bindec($binX) + 1) * -1;
+            return (string) ((bindec($binX) + 1) * -1);
         }
 
-        return bindec($binX);
+        return (string) bindec($binX);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Calculation/Engineering/ConvertUOM.php b/src/PhpSpreadsheet/Calculation/Engineering/ConvertUOM.php
index 0aafe05e..d169ae54 100644
--- a/src/PhpSpreadsheet/Calculation/Engineering/ConvertUOM.php
+++ b/src/PhpSpreadsheet/Calculation/Engineering/ConvertUOM.php
@@ -490,7 +490,7 @@ class ConvertUOM
      *    getConversionMultipliers
      * Returns an array of the Multiplier prefixes that can be used with Units of Measure in CONVERTUOM().
      *
-     * @return array of mixed
+     * @return mixed[]
      */
     public static function getConversionMultipliers()
     {
@@ -501,7 +501,7 @@ class ConvertUOM
      *    getBinaryConversionMultipliers
      * Returns an array of the additional Multiplier prefixes that can be used with Information Units of Measure in CONVERTUOM().
      *
-     * @return array of mixed
+     * @return mixed[]
      */
     public static function getBinaryConversionMultipliers()
     {
diff --git a/src/PhpSpreadsheet/Calculation/FormulaParser.php b/src/PhpSpreadsheet/Calculation/FormulaParser.php
index c11af834..cd1402fd 100644
--- a/src/PhpSpreadsheet/Calculation/FormulaParser.php
+++ b/src/PhpSpreadsheet/Calculation/FormulaParser.php
@@ -90,10 +90,8 @@ class FormulaParser
      * Get Token.
      *
      * @param int $pId Token id
-     *
-     * @return string
      */
-    public function getToken($pId = 0)
+    public function getToken(int $pId = 0): FormulaToken
     {
         if (isset($this->tokens[$pId])) {
             return $this->tokens[$pId];
diff --git a/src/PhpSpreadsheet/Calculation/Functions.php b/src/PhpSpreadsheet/Calculation/Functions.php
index 34ebefed..aea2323e 100644
--- a/src/PhpSpreadsheet/Calculation/Functions.php
+++ b/src/PhpSpreadsheet/Calculation/Functions.php
@@ -303,7 +303,7 @@ class Functions
      *
      * @param mixed $value Value to check
      *
-     * @return bool
+     * @return int|string
      */
     public static function errorType($value = '')
     {
diff --git a/src/PhpSpreadsheet/Calculation/LookupRef/Offset.php b/src/PhpSpreadsheet/Calculation/LookupRef/Offset.php
index 25ec498b..c027d83c 100644
--- a/src/PhpSpreadsheet/Calculation/LookupRef/Offset.php
+++ b/src/PhpSpreadsheet/Calculation/LookupRef/Offset.php
@@ -38,7 +38,7 @@ class Offset
      * @param mixed $width The width, in number of columns, that you want the returned reference to be.
      *                         Width must be a positive number.
      *
-     * @return array|string An array containing a cell or range of cells, or a string on error
+     * @return array|int|string An array containing a cell or range of cells, or a string on error
      */
     public static function OFFSET($cellAddress = null, $rows = 0, $columns = 0, $height = null, $width = null, ?Cell $pCell = null)
     {
diff --git a/src/PhpSpreadsheet/Calculation/MathTrig/Fact.php b/src/PhpSpreadsheet/Calculation/MathTrig/Fact.php
index 026cb9a2..298ccbac 100644
--- a/src/PhpSpreadsheet/Calculation/MathTrig/Fact.php
+++ b/src/PhpSpreadsheet/Calculation/MathTrig/Fact.php
@@ -19,7 +19,7 @@ class Fact
      *
      * @param float $factVal Factorial Value
      *
-     * @return int|string Factorial, or a string containing an error
+     * @return float|int|string Factorial, or a string containing an error
      */
     public static function funcFact($factVal)
     {
diff --git a/src/PhpSpreadsheet/Calculation/Statistical.php b/src/PhpSpreadsheet/Calculation/Statistical.php
index 003f06be..a0f4cd7c 100644
--- a/src/PhpSpreadsheet/Calculation/Statistical.php
+++ b/src/PhpSpreadsheet/Calculation/Statistical.php
@@ -729,7 +729,7 @@ class Statistical
      * @param mixed[] $newValues Values of X for which we want to find Y
      * @param bool $const a logical value specifying whether to force the intersect to equal 0
      *
-     * @return array of float
+     * @return float[]
      */
     public static function GROWTH($yValues, $xValues = [], $newValues = [], $const = true)
     {
@@ -1795,7 +1795,7 @@ class Statistical
      * @param mixed[] $newValues Values of X for which we want to find Y
      * @param bool $const a logical value specifying whether to force the intersect to equal 0
      *
-     * @return array of float
+     * @return float[]
      */
     public static function TREND($yValues, $xValues = [], $newValues = [], $const = true)
     {
diff --git a/src/PhpSpreadsheet/Calculation/Statistical/Trends.php b/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
index e745d1b7..f1fd91ae 100644
--- a/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
+++ b/src/PhpSpreadsheet/Calculation/Statistical/Trends.php
@@ -142,7 +142,7 @@ class Trends
      * @param mixed[] $newValues Values of X for which we want to find Y
      * @param mixed $const A logical (boolean) value specifying whether to force the intersect to equal 0 or not
      *
-     * @return array of float
+     * @return float[]
      */
     public static function GROWTH($yValues, $xValues = [], $newValues = [], $const = true)
     {
@@ -399,7 +399,7 @@ class Trends
      * @param mixed[] $newValues Values of X for which we want to find Y
      * @param mixed $const A logical (boolean) value specifying whether to force the intersect to equal 0 or not
      *
-     * @return array of float
+     * @return float[]
      */
     public static function TREND($yValues, $xValues = [], $newValues = [], $const = true)
     {
diff --git a/src/PhpSpreadsheet/Cell/Cell.php b/src/PhpSpreadsheet/Cell/Cell.php
index f971a3c8..89aa32cd 100644
--- a/src/PhpSpreadsheet/Cell/Cell.php
+++ b/src/PhpSpreadsheet/Cell/Cell.php
@@ -78,6 +78,7 @@ class Cell
 
     public function detach(): void
     {
+        // @phpstan-ignore-next-line
         $this->parent = null;
     }
 
@@ -201,7 +202,7 @@ class Cell
                 break;
             case DataType::TYPE_STRING2:
                 $pDataType = DataType::TYPE_STRING;
-                // no break
+            // no break
             case DataType::TYPE_STRING:
                 // Synonym for string
             case DataType::TYPE_INLINE:
@@ -563,7 +564,7 @@ class Cell
 
         // Verify if cell is in range
         return ($rangeStart[0] <= $myColumn) && ($rangeEnd[0] >= $myColumn) &&
-                ($rangeStart[1] <= $myRow) && ($rangeEnd[1] >= $myRow);
+            ($rangeStart[1] <= $myRow) && ($rangeEnd[1] >= $myRow);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Chart/Axis.php b/src/PhpSpreadsheet/Chart/Axis.php
index 6a2e2df5..27e61060 100644
--- a/src/PhpSpreadsheet/Chart/Axis.php
+++ b/src/PhpSpreadsheet/Chart/Axis.php
@@ -13,7 +13,7 @@ class Axis extends Properties
     /**
      * Axis Number.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $axisNumber = [
         'format' => self::FORMAT_CODE_GENERAL,
@@ -23,7 +23,7 @@ class Axis extends Properties
     /**
      * Axis Options.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $axisOptions = [
         'minimum' => null,
@@ -41,7 +41,7 @@ class Axis extends Properties
     /**
      * Fill Properties.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $fillProperties = [
         'type' => self::EXCEL_COLOR_TYPE_ARGB,
@@ -52,7 +52,7 @@ class Axis extends Properties
     /**
      * Line Properties.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $lineProperties = [
         'type' => self::EXCEL_COLOR_TYPE_ARGB,
@@ -63,7 +63,7 @@ class Axis extends Properties
     /**
      * Line Style Properties.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $lineStyleProperties = [
         'width' => '9525',
@@ -86,7 +86,7 @@ class Axis extends Properties
     /**
      * Shadow Properties.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $shadowProperties = [
         'presets' => self::SHADOW_PRESETS_NOSHADOW,
@@ -111,7 +111,7 @@ class Axis extends Properties
     /**
      * Glow Properties.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $glowProperties = [
         'size' => null,
@@ -125,7 +125,7 @@ class Axis extends Properties
     /**
      * Soft Edge Properties.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $softEdges = [
         'size' => null,
diff --git a/src/PhpSpreadsheet/Chart/DataSeries.php b/src/PhpSpreadsheet/Chart/DataSeries.php
index 3a44b335..067d30e5 100644
--- a/src/PhpSpreadsheet/Chart/DataSeries.php
+++ b/src/PhpSpreadsheet/Chart/DataSeries.php
@@ -75,21 +75,21 @@ class DataSeries
     /**
      * Order of plots in Series.
      *
-     * @var array of integer
+     * @var int[]
      */
     private $plotOrder = [];
 
     /**
      * Plot Label.
      *
-     * @var array of DataSeriesValues
+     * @var DataSeriesValues[]
      */
     private $plotLabel = [];
 
     /**
      * Plot Category.
      *
-     * @var array of DataSeriesValues
+     * @var DataSeriesValues[]
      */
     private $plotCategory = [];
 
@@ -103,7 +103,7 @@ class DataSeries
     /**
      * Plot Values.
      *
-     * @var array of DataSeriesValues
+     * @var DataSeriesValues[]
      */
     private $plotValues = [];
 
@@ -231,7 +231,7 @@ class DataSeries
     /**
      * Get Plot Labels.
      *
-     * @return array of DataSeriesValues
+     * @return DataSeriesValues[]
      */
     public function getPlotLabels()
     {
@@ -243,7 +243,7 @@ class DataSeries
      *
      * @param mixed $index
      *
-     * @return DataSeriesValues
+     * @return DataSeriesValues|false
      */
     public function getPlotLabelByIndex($index)
     {
@@ -260,7 +260,7 @@ class DataSeries
     /**
      * Get Plot Categories.
      *
-     * @return array of DataSeriesValues
+     * @return DataSeriesValues[]
      */
     public function getPlotCategories()
     {
@@ -272,7 +272,7 @@ class DataSeries
      *
      * @param mixed $index
      *
-     * @return DataSeriesValues
+     * @return DataSeriesValues|false
      */
     public function getPlotCategoryByIndex($index)
     {
@@ -313,7 +313,7 @@ class DataSeries
     /**
      * Get Plot Values.
      *
-     * @return array of DataSeriesValues
+     * @return DataSeriesValues[]
      */
     public function getPlotValues()
     {
@@ -325,7 +325,7 @@ class DataSeries
      *
      * @param mixed $index
      *
-     * @return DataSeriesValues
+     * @return DataSeriesValues|false
      */
     public function getPlotValuesByIndex($index)
     {
diff --git a/src/PhpSpreadsheet/Chart/DataSeriesValues.php b/src/PhpSpreadsheet/Chart/DataSeriesValues.php
index c1bd973a..88063336 100644
--- a/src/PhpSpreadsheet/Chart/DataSeriesValues.php
+++ b/src/PhpSpreadsheet/Chart/DataSeriesValues.php
@@ -55,7 +55,7 @@ class DataSeriesValues
     /**
      * Data Values.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $dataValues = [];
 
@@ -313,7 +313,7 @@ class DataSeriesValues
     /**
      * Get Series Data Values.
      *
-     * @return array of mixed
+     * @return mixed[]
      */
     public function getDataValues()
     {
diff --git a/src/PhpSpreadsheet/Chart/PlotArea.php b/src/PhpSpreadsheet/Chart/PlotArea.php
index fbd01184..ecb7b6c9 100644
--- a/src/PhpSpreadsheet/Chart/PlotArea.php
+++ b/src/PhpSpreadsheet/Chart/PlotArea.php
@@ -67,7 +67,7 @@ class PlotArea
     /**
      * Get Plot Series.
      *
-     * @return array of DataSeries
+     * @return DataSeries[]
      */
     public function getPlotGroup()
     {
diff --git a/src/PhpSpreadsheet/Collection/Cells.php b/src/PhpSpreadsheet/Collection/Cells.php
index 48f34f41..7859965b 100644
--- a/src/PhpSpreadsheet/Collection/Cells.php
+++ b/src/PhpSpreadsheet/Collection/Cells.php
@@ -19,21 +19,21 @@ class Cells
     /**
      * Parent worksheet.
      *
-     * @var Worksheet
+     * @var null|Worksheet
      */
     private $parent;
 
     /**
      * The currently active Cell.
      *
-     * @var Cell
+     * @var null|Cell
      */
     private $currentCell;
 
     /**
      * Coordinate of the currently active Cell.
      *
-     * @var string
+     * @var null|string
      */
     private $currentCoordinate;
 
diff --git a/src/PhpSpreadsheet/Document/Properties.php b/src/PhpSpreadsheet/Document/Properties.php
index 911d53ce..c099bccc 100644
--- a/src/PhpSpreadsheet/Document/Properties.php
+++ b/src/PhpSpreadsheet/Document/Properties.php
@@ -100,7 +100,7 @@ class Properties
     /**
      * Custom Properties.
      *
-     * @var string[]
+     * @var array{value: mixed, type: string}[]
      */
     private $customProperties = [];
 
diff --git a/src/PhpSpreadsheet/HashTable.php b/src/PhpSpreadsheet/HashTable.php
index 0823236c..5d4444e7 100644
--- a/src/PhpSpreadsheet/HashTable.php
+++ b/src/PhpSpreadsheet/HashTable.php
@@ -126,7 +126,7 @@ class HashTable
      *
      * @param int $pIndex
      *
-     * @return T
+     * @return null|T
      */
     public function getByIndex($pIndex)
     {
@@ -142,7 +142,7 @@ class HashTable
      *
      * @param string $pHashCode
      *
-     * @return T
+     * @return null|T
      */
     public function getByHashCode($pHashCode)
     {
diff --git a/src/PhpSpreadsheet/Reader/BaseReader.php b/src/PhpSpreadsheet/Reader/BaseReader.php
index eb0e3ba2..80348132 100644
--- a/src/PhpSpreadsheet/Reader/BaseReader.php
+++ b/src/PhpSpreadsheet/Reader/BaseReader.php
@@ -38,7 +38,7 @@ abstract class BaseReader implements IReader
      * Restrict which sheets should be loaded?
      * This property holds an array of worksheet names to be loaded. If null, then all worksheets will be loaded.
      *
-     * @var array of string
+     * @var null|string[]
      */
     protected $loadSheetsOnly;
 
diff --git a/src/PhpSpreadsheet/Reader/Xls.php b/src/PhpSpreadsheet/Reader/Xls.php
index 35b55bc0..c389105b 100644
--- a/src/PhpSpreadsheet/Reader/Xls.php
+++ b/src/PhpSpreadsheet/Reader/Xls.php
@@ -374,7 +374,7 @@ class Xls extends BaseReader
      *
      * @var int
      */
-    private $encryptionStartPos = false;
+    private $encryptionStartPos = 0;
 
     /**
      * The current RC4 decryption object.
@@ -659,7 +659,7 @@ class Xls extends BaseReader
         $this->definedname = [];
         $this->sst = [];
         $this->drawingGroupData = '';
-        $this->xfIndex = '';
+        $this->xfIndex = 0;
         $this->mapCellXfIndex = [];
         $this->mapCellStyleXfIndex = [];
 
@@ -1296,7 +1296,7 @@ class Xls extends BaseReader
                 //    TODO Provide support for named values
             }
         }
-        $this->data = null;
+        $this->data = '';
 
         return $this->spreadsheet;
     }
diff --git a/src/PhpSpreadsheet/Reader/Xlsx.php b/src/PhpSpreadsheet/Reader/Xlsx.php
index 85b6c174..cd0fd149 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx.php
@@ -879,10 +879,11 @@ class Xlsx extends BaseReader
 
                                     // Loop through contents
                                     foreach ($commentsFile->commentList->comment as $comment) {
+                                        $commentModel = $docSheet->getComment((string) $comment['ref']);
                                         if (!empty($comment['authorId'])) {
-                                            $docSheet->getComment((string) $comment['ref'])->setAuthor($authors[(string) $comment['authorId']]);
+                                            $commentModel->setAuthor($authors[$comment['authorId']]);
                                         }
-                                        $docSheet->getComment((string) $comment['ref'])->setText($this->parseRichText($comment->text));
+                                        $commentModel->setText($this->parseRichText($comment->text));
                                     }
                                 }
 
diff --git a/src/PhpSpreadsheet/Reader/Xlsx/Theme.php b/src/PhpSpreadsheet/Reader/Xlsx/Theme.php
index c105f3c1..1f2b863c 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx/Theme.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx/Theme.php
@@ -21,16 +21,16 @@ class Theme
     /**
      * Colour Map.
      *
-     * @var array of string
+     * @var string[]
      */
     private $colourMap;
 
     /**
      * Create a new Theme.
      *
-     * @param mixed $themeName
-     * @param mixed $colourSchemeName
-     * @param mixed $colourMap
+     * @param string $themeName
+     * @param string $colourSchemeName
+     * @param string[] $colourMap
      */
     public function __construct($themeName, $colourSchemeName, $colourMap)
     {
@@ -63,9 +63,9 @@ class Theme
     /**
      * Get colour Map Value by Position.
      *
-     * @param mixed $index
+     * @param int $index
      *
-     * @return string
+     * @return null|string
      */
     public function getColourByIndex($index)
     {
diff --git a/src/PhpSpreadsheet/Settings.php b/src/PhpSpreadsheet/Settings.php
index cfa50573..8fdccbad 100644
--- a/src/PhpSpreadsheet/Settings.php
+++ b/src/PhpSpreadsheet/Settings.php
@@ -118,7 +118,7 @@ class Settings
         if (self::$libXmlLoaderOptions === null && defined('LIBXML_DTDLOAD')) {
             self::setLibXmlLoaderOptions(LIBXML_DTDLOAD | LIBXML_DTDATTR);
         } elseif (self::$libXmlLoaderOptions === null) {
-            self::$libXmlLoaderOptions = true;
+            self::$libXmlLoaderOptions = 0;
         }
 
         return self::$libXmlLoaderOptions;
diff --git a/src/PhpSpreadsheet/Shared/Date.php b/src/PhpSpreadsheet/Shared/Date.php
index 49b3425c..898dd523 100644
--- a/src/PhpSpreadsheet/Shared/Date.php
+++ b/src/PhpSpreadsheet/Shared/Date.php
@@ -255,7 +255,7 @@ class Date
      *
      * @param int $dateValue Unix Timestamp
      *
-     * @return float MS Excel serialized date/time value
+     * @return false|float MS Excel serialized date/time value
      */
     public static function timestampToExcel($dateValue)
     {
diff --git a/src/PhpSpreadsheet/Shared/Drawing.php b/src/PhpSpreadsheet/Shared/Drawing.php
index 67c015c4..ebb87ed1 100644
--- a/src/PhpSpreadsheet/Shared/Drawing.php
+++ b/src/PhpSpreadsheet/Shared/Drawing.php
@@ -15,7 +15,7 @@ class Drawing
      */
     public static function pixelsToEMU($pValue)
     {
-        return round($pValue * 9525);
+        return $pValue * 9525;
     }
 
     /**
@@ -28,7 +28,7 @@ class Drawing
     public static function EMUToPixels($pValue)
     {
         if ($pValue != 0) {
-            return round($pValue / 9525);
+            return (int) round($pValue / 9525);
         }
 
         return 0;
@@ -141,7 +141,7 @@ class Drawing
     public static function angleToDegrees($pValue)
     {
         if ($pValue != 0) {
-            return round($pValue / 60000);
+            return (int) round($pValue / 60000);
         }
 
         return 0;
diff --git a/src/PhpSpreadsheet/Shared/Font.php b/src/PhpSpreadsheet/Shared/Font.php
index 94e35dfe..00629e69 100644
--- a/src/PhpSpreadsheet/Shared/Font.php
+++ b/src/PhpSpreadsheet/Shared/Font.php
@@ -268,7 +268,7 @@ class Font
         $columnWidth = Drawing::pixelsToCellDimension($columnWidth, $defaultFont);
 
         // Return
-        return round($columnWidth, 6);
+        return (int) round($columnWidth, 6);
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Shared/JAMA/LUDecomposition.php b/src/PhpSpreadsheet/Shared/JAMA/LUDecomposition.php
index e16d6a21..ecfe42ba 100644
--- a/src/PhpSpreadsheet/Shared/JAMA/LUDecomposition.php
+++ b/src/PhpSpreadsheet/Shared/JAMA/LUDecomposition.php
@@ -221,7 +221,7 @@ class LUDecomposition
     /**
      * Count determinants.
      *
-     * @return array d matrix deterninat
+     * @return float
      */
     public function det()
     {
diff --git a/src/PhpSpreadsheet/Shared/JAMA/Matrix.php b/src/PhpSpreadsheet/Shared/JAMA/Matrix.php
index 9cbc9530..adf399ac 100644
--- a/src/PhpSpreadsheet/Shared/JAMA/Matrix.php
+++ b/src/PhpSpreadsheet/Shared/JAMA/Matrix.php
@@ -147,7 +147,7 @@ class Matrix
      * @param int $i Row position
      * @param int $j Column position
      *
-     * @return mixed Element (int/float/double)
+     * @return float|int
      */
     public function get($i = null, $j = null)
     {
@@ -323,11 +323,9 @@ class Matrix
      *
      * @param int $i Row position
      * @param int $j Column position
-     * @param mixed $c Int/float/double value
-     *
-     * @return mixed Element (int/float/double)
+     * @param float|int $c value
      */
-    public function set($i = null, $j = null, $c = null)
+    public function set($i = null, $j = null, $c = null): void
     {
         // Optimized set version just has this
         $this->A[$i][$j] = $c;
diff --git a/src/PhpSpreadsheet/Shared/OLE/ChainedBlockStream.php b/src/PhpSpreadsheet/Shared/OLE/ChainedBlockStream.php
index 1863ae34..43e4804d 100644
--- a/src/PhpSpreadsheet/Shared/OLE/ChainedBlockStream.php
+++ b/src/PhpSpreadsheet/Shared/OLE/ChainedBlockStream.php
@@ -9,7 +9,7 @@ class ChainedBlockStream
     /**
      * The OLE container of the file that is being read.
      *
-     * @var OLE
+     * @var null|OLE
      */
     public $ole;
 
@@ -112,7 +112,7 @@ class ChainedBlockStream
      *
      * @param int $count maximum number of bytes to read
      *
-     * @return string
+     * @return false|string
      */
     public function stream_read($count) // @codingStandardsIgnoreLine
     {
diff --git a/src/PhpSpreadsheet/Shared/OLERead.php b/src/PhpSpreadsheet/Shared/OLERead.php
index 78417741..c4dc572a 100644
--- a/src/PhpSpreadsheet/Shared/OLERead.php
+++ b/src/PhpSpreadsheet/Shared/OLERead.php
@@ -188,7 +188,7 @@ class OLERead
      *
      * @param int $stream
      *
-     * @return string
+     * @return null|string
      */
     public function getStream($stream)
     {
diff --git a/src/PhpSpreadsheet/Shared/Trend/BestFit.php b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
index 6d6f6283..7df48953 100644
--- a/src/PhpSpreadsheet/Shared/Trend/BestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/BestFit.php
@@ -2,7 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheet\Shared\Trend;
 
-class BestFit
+abstract class BestFit
 {
     /**
      * Indicator flag for a calculation error.
@@ -96,24 +96,18 @@ class BestFit
      *
      * @param float $xValue X-Value
      *
-     * @return bool Y-Value
+     * @return float Y-Value
      */
-    public function getValueOfYForX($xValue)
-    {
-        return false;
-    }
+    abstract public function getValueOfYForX($xValue);
 
     /**
      * Return the X-Value for a specified value of Y.
      *
      * @param float $yValue Y-Value
      *
-     * @return bool X-Value
+     * @return float X-Value
      */
-    public function getValueOfXForY($yValue)
-    {
-        return false;
-    }
+    abstract public function getValueOfXForY($yValue);
 
     /**
      * Return the original set of X-Values.
@@ -130,12 +124,9 @@ class BestFit
      *
      * @param int $dp Number of places of decimal precision to display
      *
-     * @return bool
+     * @return string
      */
-    public function getEquation($dp = 0)
-    {
-        return false;
-    }
+    abstract public function getEquation($dp = 0);
 
     /**
      * Return the Slope of the line.
diff --git a/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php b/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
index 1d34e81c..2c8eea5b 100644
--- a/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
+++ b/src/PhpSpreadsheet/Shared/Trend/PolynomialBestFit.php
@@ -42,6 +42,7 @@ class PolynomialBestFit extends BestFit
     {
         $retVal = $this->getIntersect();
         $slope = $this->getSlope();
+        // @phpstan-ignore-next-line
         foreach ($slope as $key => $value) {
             if ($value != 0.0) {
                 $retVal += $value * $xValue ** ($key + 1);
@@ -76,6 +77,7 @@ class PolynomialBestFit extends BestFit
         $intersect = $this->getIntersect($dp);
 
         $equation = 'Y = ' . $intersect;
+        // @phpstan-ignore-next-line
         foreach ($slope as $key => $value) {
             if ($value != 0.0) {
                 $equation .= ' + ' . $value . ' * X';
@@ -93,7 +95,7 @@ class PolynomialBestFit extends BestFit
      *
      * @param int $dp Number of places of decimal precision to display
      *
-     * @return string
+     * @return float
      */
     public function getSlope($dp = 0)
     {
@@ -103,6 +105,7 @@ class PolynomialBestFit extends BestFit
                 $coefficients[] = round($coefficient, $dp);
             }
 
+            // @phpstan-ignore-next-line
             return $coefficients;
         }
 
diff --git a/src/PhpSpreadsheet/Shared/Xls.php b/src/PhpSpreadsheet/Shared/Xls.php
index b3cdbd7d..26035ec6 100644
--- a/src/PhpSpreadsheet/Shared/Xls.php
+++ b/src/PhpSpreadsheet/Shared/Xls.php
@@ -205,7 +205,7 @@ class Xls
      * @param int $width Width in pixels
      * @param int $height Height in pixels
      *
-     * @return array
+     * @return null|array
      */
     public static function oneAnchor2twoAnchor($sheet, $coordinates, $offsetX, $offsetY, $width, $height)
     {
@@ -245,16 +245,16 @@ class Xls
         // Bitmap isn't allowed to start or finish in a hidden cell, i.e. a cell
         // with zero height or width.
         if (self::sizeCol($sheet, Coordinate::stringFromColumnIndex($col_start)) == 0) {
-            return;
+            return null;
         }
         if (self::sizeCol($sheet, Coordinate::stringFromColumnIndex($col_end)) == 0) {
-            return;
+            return null;
         }
         if (self::sizeRow($sheet, $row_start + 1) == 0) {
-            return;
+            return null;
         }
         if (self::sizeRow($sheet, $row_end + 1) == 0) {
-            return;
+            return null;
         }
 
         // Convert the pixel values to the percentage value expected by Excel
diff --git a/src/PhpSpreadsheet/Spreadsheet.php b/src/PhpSpreadsheet/Spreadsheet.php
index 59304804..fb945399 100644
--- a/src/PhpSpreadsheet/Spreadsheet.php
+++ b/src/PhpSpreadsheet/Spreadsheet.php
@@ -69,7 +69,7 @@ class Spreadsheet
     /**
      * Named ranges.
      *
-     * @var NamedRange[]
+     * @var DefinedName[]
      */
     private $definedNames = [];
 
@@ -104,21 +104,21 @@ class Spreadsheet
     /**
      * macrosCode : all macros code as binary data (the vbaProject.bin file, this include form, code,  etc.), null if no macro.
      *
-     * @var string
+     * @var null|string
      */
     private $macrosCode;
 
     /**
      * macrosCertificate : if macros are signed, contains binary data vbaProjectSignature.bin file, null if not signed.
      *
-     * @var string
+     * @var null|string
      */
     private $macrosCertificate;
 
     /**
      * ribbonXMLData : null if workbook is'nt Excel 2007 or not contain a customized UI.
      *
-     * @var null|string
+     * @var null|array{target: string, data: string}
      */
     private $ribbonXMLData;
 
@@ -298,11 +298,9 @@ class Spreadsheet
     /**
      * retrieve ribbon XML Data.
      *
-     * return string|null|array
-     *
      * @param string $what
      *
-     * @return string
+     * @return null|array|string
      */
     public function getRibbonXMLData($what = 'all') //we need some constants here...
     {
@@ -455,7 +453,7 @@ class Spreadsheet
      *
      * @param string $pName Sheet name
      *
-     * @return Worksheet
+     * @return null|Worksheet
      */
     public function getSheetByCodeName($pName)
     {
@@ -515,12 +513,10 @@ class Spreadsheet
      */
     public function disconnectWorksheets(): void
     {
-        $worksheet = null;
-        foreach ($this->workSheetCollection as $k => &$worksheet) {
+        foreach ($this->workSheetCollection as $worksheet) {
             $worksheet->disconnectCells();
-            $this->workSheetCollection[$k] = null;
+            unset($worksheet);
         }
-        unset($worksheet);
         $this->workSheetCollection = [];
     }
 
@@ -876,7 +872,7 @@ class Spreadsheet
     /**
      * Get an array of all Named Ranges.
      *
-     * @return NamedRange[]
+     * @return DefinedName[]
      */
     public function getNamedRanges(): array
     {
@@ -891,7 +887,7 @@ class Spreadsheet
     /**
      * Get an array of all Named Formulae.
      *
-     * @return NamedFormula[]
+     * @return DefinedName[]
      */
     public function getNamedFormulae(): array
     {
@@ -1124,6 +1120,7 @@ class Spreadsheet
      */
     public function __clone()
     {
+        // @phpstan-ignore-next-line
         foreach ($this as $key => $val) {
             if (is_object($val) || (is_array($val))) {
                 $this->{$key} = unserialize(serialize($val));
diff --git a/src/PhpSpreadsheet/Style/Alignment.php b/src/PhpSpreadsheet/Style/Alignment.php
index 226a5427..e072c524 100644
--- a/src/PhpSpreadsheet/Style/Alignment.php
+++ b/src/PhpSpreadsheet/Style/Alignment.php
@@ -35,21 +35,21 @@ class Alignment extends Supervisor
     /**
      * Horizontal alignment.
      *
-     * @var string
+     * @var null|string
      */
     protected $horizontal = self::HORIZONTAL_GENERAL;
 
     /**
      * Vertical alignment.
      *
-     * @var string
+     * @var null|string
      */
     protected $vertical = self::VERTICAL_BOTTOM;
 
     /**
      * Text rotation.
      *
-     * @var int
+     * @var null|int
      */
     protected $textRotation = 0;
 
@@ -179,7 +179,7 @@ class Alignment extends Supervisor
     /**
      * Get Horizontal.
      *
-     * @return string
+     * @return null|string
      */
     public function getHorizontal()
     {
@@ -216,7 +216,7 @@ class Alignment extends Supervisor
     /**
      * Get Vertical.
      *
-     * @return string
+     * @return null|string
      */
     public function getVertical()
     {
@@ -253,7 +253,7 @@ class Alignment extends Supervisor
     /**
      * Get TextRotation.
      *
-     * @return int
+     * @return null|int
      */
     public function getTextRotation()
     {
diff --git a/src/PhpSpreadsheet/Style/Border.php b/src/PhpSpreadsheet/Style/Border.php
index dee1ad4c..a8af9d94 100644
--- a/src/PhpSpreadsheet/Style/Border.php
+++ b/src/PhpSpreadsheet/Style/Border.php
@@ -37,7 +37,7 @@ class Border extends Supervisor
     protected $color;
 
     /**
-     * @var int
+     * @var null|int
      */
     public $colorIndex;
 
diff --git a/src/PhpSpreadsheet/Style/Fill.php b/src/PhpSpreadsheet/Style/Fill.php
index 3891bc47..e793f1e7 100644
--- a/src/PhpSpreadsheet/Style/Fill.php
+++ b/src/PhpSpreadsheet/Style/Fill.php
@@ -28,19 +28,19 @@ class Fill extends Supervisor
     const FILL_PATTERN_MEDIUMGRAY = 'mediumGray';
 
     /**
-     * @var int
+     * @var null|int
      */
     public $startcolorIndex;
 
     /**
-     * @var int
+     * @var null|int
      */
     public $endcolorIndex;
 
     /**
      * Fill type.
      *
-     * @var string
+     * @var null|string
      */
     protected $fillType = self::FILL_NONE;
 
@@ -168,7 +168,7 @@ class Fill extends Supervisor
     /**
      * Get Fill Type.
      *
-     * @return string
+     * @return null|string
      */
     public function getFillType()
     {
diff --git a/src/PhpSpreadsheet/Style/Font.php b/src/PhpSpreadsheet/Style/Font.php
index ad405708..473fe1dc 100644
--- a/src/PhpSpreadsheet/Style/Font.php
+++ b/src/PhpSpreadsheet/Style/Font.php
@@ -14,56 +14,56 @@ class Font extends Supervisor
     /**
      * Font Name.
      *
-     * @var string
+     * @var null|string
      */
     protected $name = 'Calibri';
 
     /**
      * Font Size.
      *
-     * @var float
+     * @var null|float
      */
     protected $size = 11;
 
     /**
      * Bold.
      *
-     * @var bool
+     * @var null|bool
      */
     protected $bold = false;
 
     /**
      * Italic.
      *
-     * @var bool
+     * @var null|bool
      */
     protected $italic = false;
 
     /**
      * Superscript.
      *
-     * @var bool
+     * @var null|bool
      */
     protected $superscript = false;
 
     /**
      * Subscript.
      *
-     * @var bool
+     * @var null|bool
      */
     protected $subscript = false;
 
     /**
      * Underline.
      *
-     * @var string
+     * @var null|string
      */
     protected $underline = self::UNDERLINE_NONE;
 
     /**
      * Strikethrough.
      *
-     * @var bool
+     * @var null|bool
      */
     protected $strikethrough = false;
 
@@ -75,7 +75,7 @@ class Font extends Supervisor
     protected $color;
 
     /**
-     * @var int
+     * @var null|int
      */
     public $colorIndex;
 
@@ -199,7 +199,7 @@ class Font extends Supervisor
     /**
      * Get Name.
      *
-     * @return string
+     * @return null|string
      */
     public function getName()
     {
@@ -235,7 +235,7 @@ class Font extends Supervisor
     /**
      * Get Size.
      *
-     * @return float
+     * @return null|float
      */
     public function getSize()
     {
@@ -271,7 +271,7 @@ class Font extends Supervisor
     /**
      * Get Bold.
      *
-     * @return bool
+     * @return null|bool
      */
     public function getBold()
     {
@@ -307,7 +307,7 @@ class Font extends Supervisor
     /**
      * Get Italic.
      *
-     * @return bool
+     * @return null|bool
      */
     public function getItalic()
     {
@@ -343,7 +343,7 @@ class Font extends Supervisor
     /**
      * Get Superscript.
      *
-     * @return bool
+     * @return null|bool
      */
     public function getSuperscript()
     {
@@ -377,7 +377,7 @@ class Font extends Supervisor
     /**
      * Get Subscript.
      *
-     * @return bool
+     * @return null|bool
      */
     public function getSubscript()
     {
@@ -411,7 +411,7 @@ class Font extends Supervisor
     /**
      * Get Underline.
      *
-     * @return string
+     * @return null|string
      */
     public function getUnderline()
     {
@@ -451,7 +451,7 @@ class Font extends Supervisor
     /**
      * Get Strikethrough.
      *
-     * @return bool
+     * @return null|bool
      */
     public function getStrikethrough()
     {
diff --git a/src/PhpSpreadsheet/Style/NumberFormat.php b/src/PhpSpreadsheet/Style/NumberFormat.php
index b5cc05f4..6235d864 100644
--- a/src/PhpSpreadsheet/Style/NumberFormat.php
+++ b/src/PhpSpreadsheet/Style/NumberFormat.php
@@ -64,14 +64,14 @@ class NumberFormat extends Supervisor
     /**
      * Format Code.
      *
-     * @var string
+     * @var null|string
      */
     protected $formatCode = self::FORMAT_GENERAL;
 
     /**
      * Built-in format Code.
      *
-     * @var string
+     * @var false|int
      */
     protected $builtInFormatCode = 0;
 
@@ -150,7 +150,7 @@ class NumberFormat extends Supervisor
     /**
      * Get Format Code.
      *
-     * @return string
+     * @return null|string
      */
     public function getFormatCode()
     {
@@ -190,7 +190,7 @@ class NumberFormat extends Supervisor
     /**
      * Get Built-In Format Code.
      *
-     * @return int
+     * @return false|int
      */
     public function getBuiltInFormatCode()
     {
diff --git a/src/PhpSpreadsheet/Worksheet/AutoFilter.php b/src/PhpSpreadsheet/Worksheet/AutoFilter.php
index d8912b21..1a710e40 100644
--- a/src/PhpSpreadsheet/Worksheet/AutoFilter.php
+++ b/src/PhpSpreadsheet/Worksheet/AutoFilter.php
@@ -14,7 +14,7 @@ class AutoFilter
     /**
      * Autofilter Worksheet.
      *
-     * @var Worksheet
+     * @var null|Worksheet
      */
     private $workSheet;
 
@@ -47,7 +47,7 @@ class AutoFilter
     /**
      * Get AutoFilter Parent Worksheet.
      *
-     * @return Worksheet
+     * @return null|Worksheet
      */
     public function getParent()
     {
@@ -791,10 +791,10 @@ class AutoFilter
                     if ($ruleOperator === AutoFilter\Column\Rule::AUTOFILTER_COLUMN_RULE_TOPTEN_PERCENT) {
                         $ruleValue = floor($ruleValue * ($dataRowCount / 100));
                     }
-                    if ($ruleValue < 1) {
+                    if (!is_array($ruleValue) && $ruleValue < 1) {
                         $ruleValue = 1;
                     }
-                    if ($ruleValue > 500) {
+                    if (!is_array($ruleValue) && $ruleValue > 500) {
                         $ruleValue = 500;
                     }
 
diff --git a/src/PhpSpreadsheet/Worksheet/AutoFilter/Column.php b/src/PhpSpreadsheet/Worksheet/AutoFilter/Column.php
index 09584a7a..8ec0ca3b 100644
--- a/src/PhpSpreadsheet/Worksheet/AutoFilter/Column.php
+++ b/src/PhpSpreadsheet/Worksheet/AutoFilter/Column.php
@@ -49,7 +49,7 @@ class Column
     /**
      * Autofilter.
      *
-     * @var AutoFilter
+     * @var null|AutoFilter
      */
     private $parent;
 
@@ -77,14 +77,14 @@ class Column
     /**
      * Autofilter Column Rules.
      *
-     * @var array of Column\Rule
+     * @var Column\Rule[]
      */
     private $ruleset = [];
 
     /**
      * Autofilter Column Dynamic Attributes.
      *
-     * @var array of mixed
+     * @var mixed[]
      */
     private $attributes = [];
 
@@ -133,7 +133,7 @@ class Column
     /**
      * Get this Column's AutoFilter Parent.
      *
-     * @return AutoFilter
+     * @return null|AutoFilter
      */
     public function getParent()
     {
@@ -256,7 +256,7 @@ class Column
      *
      * @param string $pName Attribute Name
      *
-     * @return string
+     * @return null|string
      */
     public function getAttribute($pName)
     {
diff --git a/src/PhpSpreadsheet/Worksheet/AutoFilter/Column/Rule.php b/src/PhpSpreadsheet/Worksheet/AutoFilter/Column/Rule.php
index 1aacb0cb..330a1641 100644
--- a/src/PhpSpreadsheet/Worksheet/AutoFilter/Column/Rule.php
+++ b/src/PhpSpreadsheet/Worksheet/AutoFilter/Column/Rule.php
@@ -217,7 +217,7 @@ class Rule
     /**
      * Autofilter Rule Value.
      *
-     * @var string
+     * @var string|string[]
      */
     private $value = '';
 
@@ -276,7 +276,7 @@ class Rule
     /**
      * Get AutoFilter Rule Value.
      *
-     * @return string
+     * @return string|string[]
      */
     public function getValue()
     {
diff --git a/src/PhpSpreadsheet/Worksheet/BaseDrawing.php b/src/PhpSpreadsheet/Worksheet/BaseDrawing.php
index be2f23df..5829671b 100644
--- a/src/PhpSpreadsheet/Worksheet/BaseDrawing.php
+++ b/src/PhpSpreadsheet/Worksheet/BaseDrawing.php
@@ -39,7 +39,7 @@ class BaseDrawing implements IComparable
     /**
      * Worksheet.
      *
-     * @var Worksheet
+     * @var null|Worksheet
      */
     protected $worksheet;
 
@@ -190,7 +190,7 @@ class BaseDrawing implements IComparable
     /**
      * Get Worksheet.
      *
-     * @return Worksheet
+     * @return null|Worksheet
      */
     public function getWorksheet()
     {
@@ -330,7 +330,7 @@ class BaseDrawing implements IComparable
         // Resize proportional?
         if ($this->resizeProportional && $pValue != 0) {
             $ratio = $this->height / ($this->width != 0 ? $this->width : 1);
-            $this->height = round($ratio * $pValue);
+            $this->height = (int) round($ratio * $pValue);
         }
 
         // Set width
@@ -361,7 +361,7 @@ class BaseDrawing implements IComparable
         // Resize proportional?
         if ($this->resizeProportional && $pValue != 0) {
             $ratio = $this->width / ($this->height != 0 ? $this->height : 1);
-            $this->width = round($ratio * $pValue);
+            $this->width = (int) round($ratio * $pValue);
         }
 
         // Set height
@@ -392,10 +392,10 @@ class BaseDrawing implements IComparable
         $yratio = $height / ($this->height != 0 ? $this->height : 1);
         if ($this->resizeProportional && !($width == 0 || $height == 0)) {
             if (($xratio * $this->height) < $height) {
-                $this->height = ceil($xratio * $this->height);
+                $this->height = (int) ceil($xratio * $this->height);
                 $this->width = $width;
             } else {
-                $this->width = ceil($yratio * $this->width);
+                $this->width = (int) ceil($yratio * $this->width);
                 $this->height = $height;
             }
         } else {
diff --git a/src/PhpSpreadsheet/Worksheet/CellIterator.php b/src/PhpSpreadsheet/Worksheet/CellIterator.php
index e0f35b64..31f6ae65 100644
--- a/src/PhpSpreadsheet/Worksheet/CellIterator.php
+++ b/src/PhpSpreadsheet/Worksheet/CellIterator.php
@@ -25,6 +25,7 @@ abstract class CellIterator implements Iterator
      */
     public function __destruct()
     {
+        // @phpstan-ignore-next-line
         $this->worksheet = null;
     }
 
diff --git a/src/PhpSpreadsheet/Worksheet/Column.php b/src/PhpSpreadsheet/Worksheet/Column.php
index 763806a0..8abbabe5 100644
--- a/src/PhpSpreadsheet/Worksheet/Column.php
+++ b/src/PhpSpreadsheet/Worksheet/Column.php
@@ -36,6 +36,7 @@ class Column
      */
     public function __destruct()
     {
+        // @phpstan-ignore-next-line
         $this->parent = null;
     }
 
diff --git a/src/PhpSpreadsheet/Worksheet/ColumnCellIterator.php b/src/PhpSpreadsheet/Worksheet/ColumnCellIterator.php
index 1390214e..65772114 100644
--- a/src/PhpSpreadsheet/Worksheet/ColumnCellIterator.php
+++ b/src/PhpSpreadsheet/Worksheet/ColumnCellIterator.php
@@ -18,7 +18,7 @@ class ColumnCellIterator extends CellIterator
     /**
      * Column index.
      *
-     * @var string
+     * @var int
      */
     private $columnIndex;
 
diff --git a/src/PhpSpreadsheet/Worksheet/ColumnIterator.php b/src/PhpSpreadsheet/Worksheet/ColumnIterator.php
index a7466881..0651a7a4 100644
--- a/src/PhpSpreadsheet/Worksheet/ColumnIterator.php
+++ b/src/PhpSpreadsheet/Worksheet/ColumnIterator.php
@@ -57,6 +57,7 @@ class ColumnIterator implements Iterator
      */
     public function __destruct()
     {
+        // @phpstan-ignore-next-line
         $this->worksheet = null;
     }
 
diff --git a/src/PhpSpreadsheet/Worksheet/Drawing/Shadow.php b/src/PhpSpreadsheet/Worksheet/Drawing/Shadow.php
index 01ffed94..0557c83c 100644
--- a/src/PhpSpreadsheet/Worksheet/Drawing/Shadow.php
+++ b/src/PhpSpreadsheet/Worksheet/Drawing/Shadow.php
@@ -52,7 +52,7 @@ class Shadow implements IComparable
     /**
      * Shadow alignment.
      *
-     * @var int
+     * @var string
      */
     private $alignment;
 
@@ -184,7 +184,7 @@ class Shadow implements IComparable
     /**
      * Get Shadow alignment.
      *
-     * @return int
+     * @return string
      */
     public function getAlignment()
     {
@@ -194,7 +194,7 @@ class Shadow implements IComparable
     /**
      * Set Shadow alignment.
      *
-     * @param int $pValue
+     * @param string $pValue
      *
      * @return $this
      */
diff --git a/src/PhpSpreadsheet/Worksheet/Iterator.php b/src/PhpSpreadsheet/Worksheet/Iterator.php
index 93b0bb04..134b619a 100644
--- a/src/PhpSpreadsheet/Worksheet/Iterator.php
+++ b/src/PhpSpreadsheet/Worksheet/Iterator.php
@@ -29,14 +29,6 @@ class Iterator implements \Iterator
         $this->subject = $subject;
     }
 
-    /**
-     * Destructor.
-     */
-    public function __destruct()
-    {
-        $this->subject = null;
-    }
-
     /**
      * Rewind iterator.
      */
diff --git a/src/PhpSpreadsheet/Worksheet/MemoryDrawing.php b/src/PhpSpreadsheet/Worksheet/MemoryDrawing.php
index fb002114..cde23c96 100644
--- a/src/PhpSpreadsheet/Worksheet/MemoryDrawing.php
+++ b/src/PhpSpreadsheet/Worksheet/MemoryDrawing.php
@@ -52,7 +52,6 @@ class MemoryDrawing extends BaseDrawing
     public function __construct()
     {
         // Initialise values
-        $this->imageResource = null;
         $this->renderingFunction = self::RENDERING_DEFAULT;
         $this->mimeType = self::MIMETYPE_DEFAULT;
         $this->uniqueName = md5(mt_rand(0, 9999) . time() . mt_rand(0, 9999));
diff --git a/src/PhpSpreadsheet/Worksheet/PageSetup.php b/src/PhpSpreadsheet/Worksheet/PageSetup.php
index d1a22a7b..7f3f71dc 100644
--- a/src/PhpSpreadsheet/Worksheet/PageSetup.php
+++ b/src/PhpSpreadsheet/Worksheet/PageSetup.php
@@ -238,7 +238,7 @@ class PageSetup
     /**
      * Print area.
      *
-     * @var string
+     * @var null|string
      */
     private $printArea;
 
diff --git a/src/PhpSpreadsheet/Worksheet/Row.php b/src/PhpSpreadsheet/Worksheet/Row.php
index cf935743..01053c39 100644
--- a/src/PhpSpreadsheet/Worksheet/Row.php
+++ b/src/PhpSpreadsheet/Worksheet/Row.php
@@ -36,6 +36,7 @@ class Row
      */
     public function __destruct()
     {
+        // @phpstan-ignore-next-line
         $this->worksheet = null;
     }
 
diff --git a/src/PhpSpreadsheet/Worksheet/RowIterator.php b/src/PhpSpreadsheet/Worksheet/RowIterator.php
index 469c284c..7d49f1ac 100644
--- a/src/PhpSpreadsheet/Worksheet/RowIterator.php
+++ b/src/PhpSpreadsheet/Worksheet/RowIterator.php
@@ -50,14 +50,6 @@ class RowIterator implements Iterator
         $this->resetStart($startRow);
     }
 
-    /**
-     * Destructor.
-     */
-    public function __destruct()
-    {
-        $this->subject = null;
-    }
-
     /**
      * (Re)Set the start row and the current row pointer.
      *
diff --git a/src/PhpSpreadsheet/Worksheet/Worksheet.php b/src/PhpSpreadsheet/Worksheet/Worksheet.php
index f8b6a743..02d7692b 100644
--- a/src/PhpSpreadsheet/Worksheet/Worksheet.php
+++ b/src/PhpSpreadsheet/Worksheet/Worksheet.php
@@ -105,7 +105,7 @@ class Worksheet implements IComparable
      *
      * @var ArrayObject<Chart>
      */
-    private $chartCollection = [];
+    private $chartCollection;
 
     /**
      * Worksheet title.
@@ -278,9 +278,9 @@ class Worksheet implements IComparable
     /**
      * Cached highest column.
      *
-     * @var string
+     * @var int
      */
-    private $cachedHighestColumn = 'A';
+    private $cachedHighestColumn = 1;
 
     /**
      * Cached highest row.
@@ -313,7 +313,7 @@ class Worksheet implements IComparable
     /**
      * Tab color.
      *
-     * @var Color
+     * @var null|Color
      */
     private $tabColor;
 
@@ -383,9 +383,11 @@ class Worksheet implements IComparable
     {
         if ($this->cellCollection !== null) {
             $this->cellCollection->unsetWorksheetCells();
+            // @phpstan-ignore-next-line
             $this->cellCollection = null;
         }
         //    detach ourself from the workbook, so that it can then delete this worksheet successfully
+        // @phpstan-ignore-next-line
         $this->parent = null;
     }
 
@@ -1039,7 +1041,7 @@ class Worksheet implements IComparable
     public function getHighestColumn($row = null)
     {
         if ($row == null) {
-            return $this->cachedHighestColumn;
+            return Coordinate::stringFromColumnIndex($this->cachedHighestColumn);
         }
 
         return $this->getHighestDataColumn($row);
@@ -1252,11 +1254,12 @@ class Worksheet implements IComparable
 
         // Coordinates
         $aCoordinates = Coordinate::coordinateFromString($pCoordinate);
-        if (Coordinate::columnIndexFromString($this->cachedHighestColumn) < Coordinate::columnIndexFromString($aCoordinates[0])) {
-            $this->cachedHighestColumn = $aCoordinates[0];
+        $aIndexes = Coordinate::indexesFromString($pCoordinate);
+        if ($this->cachedHighestColumn < $aIndexes[0]) {
+            $this->cachedHighestColumn = $aIndexes[0];
         }
-        if ($aCoordinates[1] > $this->cachedHighestRow) {
-            $this->cachedHighestRow = $aCoordinates[1];
+        if ($aIndexes[1] > $this->cachedHighestRow) {
+            $this->cachedHighestRow = $aIndexes[1];
         }
 
         // Cell needs appropriate xfIndex from dimensions records
@@ -1377,8 +1380,9 @@ class Worksheet implements IComparable
             }
             $this->columnDimensions[$pColumn] = new ColumnDimension($pColumn);
 
-            if (Coordinate::columnIndexFromString($this->cachedHighestColumn) < Coordinate::columnIndexFromString($pColumn)) {
-                $this->cachedHighestColumn = $pColumn;
+            $columnIndex = Coordinate::columnIndexFromString($pColumn);
+            if ($this->cachedHighestColumn < $columnIndex) {
+                $this->cachedHighestColumn = $columnIndex;
             }
         }
 
@@ -1987,7 +1991,7 @@ class Worksheet implements IComparable
     /**
      * Get the default position of the right bottom pane.
      *
-     * @return int
+     * @return null|string
      */
     public function getTopLeftCell()
     {
@@ -2677,9 +2681,9 @@ class Worksheet implements IComparable
 
         // Cache values
         if ($highestColumn < 1) {
-            $this->cachedHighestColumn = 'A';
+            $this->cachedHighestColumn = 1;
         } else {
-            $this->cachedHighestColumn = Coordinate::stringFromColumnIndex($highestColumn);
+            $this->cachedHighestColumn = $highestColumn;
         }
         $this->cachedHighestRow = $highestRow;
 
@@ -2905,7 +2909,6 @@ class Worksheet implements IComparable
     public function resetTabColor()
     {
         $this->tabColor = null;
-        $this->tabColor = null;
 
         return $this;
     }
@@ -2935,6 +2938,7 @@ class Worksheet implements IComparable
      */
     public function __clone()
     {
+        // @phpstan-ignore-next-line
         foreach ($this as $key => $val) {
             if ($key == 'parent') {
                 continue;
diff --git a/src/PhpSpreadsheet/Writer/Html.php b/src/PhpSpreadsheet/Writer/Html.php
index 60612737..4ee94114 100644
--- a/src/PhpSpreadsheet/Writer/Html.php
+++ b/src/PhpSpreadsheet/Writer/Html.php
@@ -37,7 +37,7 @@ class Html extends BaseWriter
     /**
      * Sheet index to write.
      *
-     * @var int
+     * @var null|int
      */
     private $sheetIndex = 0;
 
@@ -735,7 +735,7 @@ class Html extends BaseWriter
                 if ($chartCoordinates['cell'] == $coordinates) {
                     $chartFileName = File::sysGetTempDir() . '/' . uniqid('', true) . '.png';
                     if (!$chart->render($chartFileName)) {
-                        return;
+                        return '';
                     }
 
                     $html .= PHP_EOL;
diff --git a/src/PhpSpreadsheet/Writer/Pdf.php b/src/PhpSpreadsheet/Writer/Pdf.php
index 87220458..36f3966d 100644
--- a/src/PhpSpreadsheet/Writer/Pdf.php
+++ b/src/PhpSpreadsheet/Writer/Pdf.php
@@ -165,7 +165,7 @@ abstract class Pdf extends Html
     /**
      * Set Paper Size.
      *
-     * @param string $pValue Paper size see PageSetup::PAPERSIZE_*
+     * @param int $pValue Paper size see PageSetup::PAPERSIZE_*
      *
      * @return self
      */
diff --git a/src/PhpSpreadsheet/Writer/Xls.php b/src/PhpSpreadsheet/Writer/Xls.php
index 1ee52bdf..a1b477bf 100644
--- a/src/PhpSpreadsheet/Writer/Xls.php
+++ b/src/PhpSpreadsheet/Writer/Xls.php
@@ -81,14 +81,14 @@ class Xls extends BaseWriter
     /**
      * Basic OLE object summary information.
      *
-     * @var array
+     * @var string
      */
     private $summaryInformation;
 
     /**
      * Extended OLE object document summary information.
      *
-     * @var array
+     * @var string
      */
     private $documentSummaryInformation;
 
@@ -727,6 +727,7 @@ class Xls extends BaseWriter
             } elseif ($dataProp['type']['data'] == 0x1E) { // null-terminated string prepended by dword string length
                 // Null-terminated string
                 $dataProp['data']['data'] .= chr(0);
+                // @phpstan-ignore-next-line
                 ++$dataProp['data']['length'];
                 // Complete the string with null string for being a %4
                 $dataProp['data']['length'] = $dataProp['data']['length'] + ((4 - $dataProp['data']['length'] % 4) == 4 ? 0 : (4 - $dataProp['data']['length'] % 4));
@@ -744,6 +745,7 @@ class Xls extends BaseWriter
             } else {
                 $dataSection_Content .= $dataProp['data']['data'];
 
+                // @phpstan-ignore-next-line
                 $dataSection_Content_Offset += 4 + $dataProp['data']['length'];
             }
         }
diff --git a/src/PhpSpreadsheet/Writer/Xls/BIFFwriter.php b/src/PhpSpreadsheet/Writer/Xls/BIFFwriter.php
index 84e27d0d..4a7e0656 100644
--- a/src/PhpSpreadsheet/Writer/Xls/BIFFwriter.php
+++ b/src/PhpSpreadsheet/Writer/Xls/BIFFwriter.php
@@ -49,7 +49,7 @@ class BIFFwriter
     /**
      * The string containing the data of the BIFF stream.
      *
-     * @var string
+     * @var null|string
      */
     public $_data;
 
diff --git a/src/PhpSpreadsheet/Writer/Xls/Font.php b/src/PhpSpreadsheet/Writer/Xls/Font.php
index 9cb31ead..1266cf24 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Font.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Font.php
@@ -119,7 +119,7 @@ class Font
     /**
      * Map of BIFF2-BIFF8 codes for underline styles.
      *
-     * @var array of int
+     * @var int[]
      */
     private static $mapUnderline = [
         \PhpOffice\PhpSpreadsheet\Style\Font::UNDERLINE_NONE => 0x00,
diff --git a/src/PhpSpreadsheet/Writer/Xls/Worksheet.php b/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
index fdc05b85..7051ab2d 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
@@ -95,7 +95,7 @@ class Worksheet extends BIFFwriter
     /**
      * Whether to use outline.
      *
-     * @var int
+     * @var bool
      */
     private $outlineOn;
 
@@ -244,10 +244,10 @@ class Worksheet extends BIFFwriter
 
         $this->printHeaders = 0;
 
-        $this->outlineStyle = 0;
-        $this->outlineBelow = 1;
-        $this->outlineRight = 1;
-        $this->outlineOn = 1;
+        $this->outlineStyle = false;
+        $this->outlineBelow = true;
+        $this->outlineRight = true;
+        $this->outlineOn = true;
 
         $this->fontHashIndex = [];
 
@@ -594,15 +594,13 @@ class Worksheet extends BIFFwriter
     }
 
     /**
-     * Retrieves data from memory in one chunk, or from disk in $buffer
+     * Retrieves data from memory in one chunk, or from disk
      * sized chunks.
      *
      * @return string The data
      */
     public function getData()
     {
-        $buffer = 4096;
-
         // Return data stored in memory
         if (isset($this->_data)) {
             $tmp = $this->_data;
@@ -612,7 +610,7 @@ class Worksheet extends BIFFwriter
         }
 
         // No data to return
-        return false;
+        return '';
     }
 
     /**
@@ -640,11 +638,6 @@ class Worksheet extends BIFFwriter
         $this->outlineBelow = $symbols_below;
         $this->outlineRight = $symbols_right;
         $this->outlineStyle = $auto_style;
-
-        // Ensure this is a boolean vale for Window2
-        if ($this->outlineOn) {
-            $this->outlineOn = 1;
-        }
     }
 
     /**
@@ -926,20 +919,14 @@ class Worksheet extends BIFFwriter
      * The hyperlink can be to a http, ftp, mail, internal sheet (not yet), or external
      * directory url.
      *
-     * Returns  0 : normal termination
-     *         -2 : row or column out of range
-     *         -3 : long string truncated to 255 chars
-     *
      * @param int $row Row
      * @param int $col Column
      * @param string $url URL string
-     *
-     * @return int
      */
-    private function writeUrl($row, $col, $url)
+    private function writeUrl($row, $col, $url): void
     {
         // Add start row and col to arg list
-        return $this->writeUrlRange($row, $col, $row, $col, $url);
+        $this->writeUrlRange($row, $col, $row, $col, $url);
     }
 
     /**
@@ -954,21 +941,19 @@ class Worksheet extends BIFFwriter
      * @param int $col2 End column
      * @param string $url URL string
      *
-     * @return int
-     *
      * @see writeUrl()
      */
-    public function writeUrlRange($row1, $col1, $row2, $col2, $url)
+    private function writeUrlRange($row1, $col1, $row2, $col2, $url): void
     {
         // Check for internal/external sheet links or default to web link
         if (preg_match('[^internal:]', $url)) {
-            return $this->writeUrlInternal($row1, $col1, $row2, $col2, $url);
+            $this->writeUrlInternal($row1, $col1, $row2, $col2, $url);
         }
         if (preg_match('[^external:]', $url)) {
-            return $this->writeUrlExternal($row1, $col1, $row2, $col2, $url);
+            $this->writeUrlExternal($row1, $col1, $row2, $col2, $url);
         }
 
-        return $this->writeUrlWeb($row1, $col1, $row2, $col2, $url);
+        $this->writeUrlWeb($row1, $col1, $row2, $col2, $url);
     }
 
     /**
@@ -982,14 +967,11 @@ class Worksheet extends BIFFwriter
      * @param int $col2 End column
      * @param string $url URL string
      *
-     * @return int
-     *
      * @see writeUrl()
      */
-    public function writeUrlWeb($row1, $col1, $row2, $col2, $url)
+    public function writeUrlWeb($row1, $col1, $row2, $col2, $url): void
     {
         $record = 0x01B8; // Record identifier
-        $length = 0x00000; // Bytes to follow
 
         // Pack the undocumented parts of the hyperlink stream
         $unknown1 = pack('H*', 'D0C9EA79F9BACE118C8200AA004BA90B02000000');
@@ -1014,8 +996,6 @@ class Worksheet extends BIFFwriter
 
         // Write the packed data
         $this->append($header . $data . $unknown1 . $options . $unknown2 . $url_len . $url);
-
-        return 0;
     }
 
     /**
@@ -1027,14 +1007,11 @@ class Worksheet extends BIFFwriter
      * @param int $col2 End column
      * @param string $url URL string
      *
-     * @return int
-     *
      * @see writeUrl()
      */
-    public function writeUrlInternal($row1, $col1, $row2, $col2, $url)
+    private function writeUrlInternal($row1, $col1, $row2, $col2, $url): void
     {
         $record = 0x01B8; // Record identifier
-        $length = 0x00000; // Bytes to follow
 
         // Strip URL type
         $url = preg_replace('/^internal:/', '', $url);
@@ -1063,8 +1040,6 @@ class Worksheet extends BIFFwriter
 
         // Write the packed data
         $this->append($header . $data . $unknown1 . $options . $url_len . $url);
-
-        return 0;
     }
 
     /**
@@ -1080,16 +1055,14 @@ class Worksheet extends BIFFwriter
      * @param int $col2 End column
      * @param string $url URL string
      *
-     * @return int
-     *
      * @see writeUrl()
      */
-    public function writeUrlExternal($row1, $col1, $row2, $col2, $url)
+    private function writeUrlExternal($row1, $col1, $row2, $col2, $url): void
     {
         // Network drives are different. We will handle them separately
         // MS/Novell network drives and shares start with \\
         if (preg_match('[^external:\\\\]', $url)) {
-            return; //($this->writeUrlExternal_net($row1, $col1, $row2, $col2, $url, $str, $format));
+            return;
         }
 
         $record = 0x01B8; // Record identifier
@@ -1165,8 +1138,6 @@ class Worksheet extends BIFFwriter
 
         // Write the packed data
         $this->append($header . $data);
-
-        return 0;
     }
 
     /**
diff --git a/src/PhpSpreadsheet/Writer/Xls/Xf.php b/src/PhpSpreadsheet/Writer/Xls/Xf.php
index eca3d8e0..6f1d1cb2 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Xf.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Xf.php
@@ -362,7 +362,7 @@ class Xf
     /**
      * Map of BIFF2-BIFF8 codes for border styles.
      *
-     * @var array of int
+     * @var int[]
      */
     private static $mapBorderStyles = [
         Border::BORDER_NONE => 0x00,
@@ -396,7 +396,7 @@ class Xf
     /**
      * Map of BIFF2-BIFF8 codes for fill types.
      *
-     * @var array of int
+     * @var int[]
      */
     private static $mapFillTypes = [
         Fill::FILL_NONE => 0x00,
@@ -437,7 +437,7 @@ class Xf
     /**
      * Map of BIFF2-BIFF8 codes for horizontal alignment.
      *
-     * @var array of int
+     * @var int[]
      */
     private static $mapHAlignments = [
         Alignment::HORIZONTAL_GENERAL => 0,
@@ -464,7 +464,7 @@ class Xf
     /**
      * Map of BIFF2-BIFF8 codes for vertical alignment.
      *
-     * @var array of int
+     * @var int[]
      */
     private static $mapVAlignments = [
         Alignment::VERTICAL_TOP => 0,
diff --git a/src/PhpSpreadsheet/Writer/Xlsx.php b/src/PhpSpreadsheet/Writer/Xlsx.php
index 61351ed8..27ceb559 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx.php
@@ -200,12 +200,19 @@ class Xlsx extends BaseWriter
         $this->writerPartWorksheet = new Worksheet($this);
 
         // Set HashTable variables
+        // @phpstan-ignore-next-line
         $this->bordersHashTable = new HashTable();
+        // @phpstan-ignore-next-line
         $this->drawingHashTable = new HashTable();
+        // @phpstan-ignore-next-line
         $this->fillHashTable = new HashTable();
+        // @phpstan-ignore-next-line
         $this->fontHashTable = new HashTable();
+        // @phpstan-ignore-next-line
         $this->numFmtHashTable = new HashTable();
+        // @phpstan-ignore-next-line
         $this->styleHashTable = new HashTable();
+        // @phpstan-ignore-next-line
         $this->stylesConditionalHashTable = new HashTable();
     }
 
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/DocProps.php b/src/PhpSpreadsheet/Writer/Xlsx/DocProps.php
index bcbc2379..6332a34d 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/DocProps.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/DocProps.php
@@ -170,13 +170,13 @@ class DocProps extends WriterPart
     /**
      * Write docProps/custom.xml to XML format.
      *
-     * @return string XML Output
+     * @return null|string XML Output
      */
     public function writeDocPropsCustom(Spreadsheet $spreadsheet)
     {
         $customPropertyList = $spreadsheet->getProperties()->getCustomProperties();
         if (empty($customPropertyList)) {
-            return;
+            return null;
         }
 
         // Create XML writer
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Theme.php b/src/PhpSpreadsheet/Writer/Xlsx/Theme.php
index dfde302c..99177292 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Theme.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Theme.php
@@ -10,7 +10,7 @@ class Theme extends WriterPart
     /**
      * Map of Major fonts to write.
      *
-     * @var array of string
+     * @var string[]
      */
     private static $majorFonts = [
         'Jpan' => 'ＭＳ Ｐゴシック',
@@ -48,7 +48,7 @@ class Theme extends WriterPart
     /**
      * Map of Minor fonts to write.
      *
-     * @var array of string
+     * @var string[]
      */
     private static $minorFonts = [
         'Jpan' => 'ＭＳ Ｐゴシック',
@@ -86,7 +86,7 @@ class Theme extends WriterPart
     /**
      * Map of core colours.
      *
-     * @var array of string
+     * @var string[]
      */
     private static $colourScheme = [
         'dk2' => '1F497D',
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php
index bc3a3918..af96c18e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php
@@ -22,11 +22,6 @@ class ImConjugateTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMCONJUGATE
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php
index 693f0bab..c00bafda 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php
@@ -22,11 +22,6 @@ class ImCosTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMCOS
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php
index ae035fef..6f84217a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php
@@ -22,11 +22,6 @@ class ImCoshTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMCOSH
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php
index 8b888b3f..cbadfd8a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php
@@ -22,11 +22,6 @@ class ImCotTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMCOT
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php
index 5a08c0b6..65782e32 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php
@@ -22,11 +22,6 @@ class ImCscTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMCSC
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php
index a95a4eaf..ef1c06ea 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php
@@ -22,11 +22,6 @@ class ImCschTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMCSCH
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php
index 2bc91619..0943f408 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php
@@ -22,11 +22,6 @@ class ImDivTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMDIV
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php
index 7debbc9c..5f5edfd3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php
@@ -22,11 +22,6 @@ class ImExpTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMEXP
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php
index 3e270975..36ca116a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php
@@ -22,11 +22,6 @@ class ImLnTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMLN
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php
index 2a4db7fb..9a37d85c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php
@@ -22,11 +22,6 @@ class ImLog10Test extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMLOG10
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php
index 53b302dd..f0d853ba 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php
@@ -22,11 +22,6 @@ class ImLog2Test extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMLOG2
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php
index 41e52878..4493515c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php
@@ -22,11 +22,6 @@ class ImPowerTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMPOWER
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php
index 43495739..395153ed 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php
@@ -22,11 +22,6 @@ class ImProductTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMPRODUCT
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php
index e785d3ac..bd9c6df0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php
@@ -22,11 +22,6 @@ class ImSecTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSEC
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php
index 22cb6fae..b81e0305 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php
@@ -22,11 +22,6 @@ class ImSechTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSECH
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php
index dd797a35..d83980e0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php
@@ -22,11 +22,6 @@ class ImSinTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSIN
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php
index 4174d1c0..107c0949 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php
@@ -22,11 +22,6 @@ class ImSinhTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSINH
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php
index 091b11c5..c8c83e10 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php
@@ -22,11 +22,6 @@ class ImSqrtTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSQRT
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php
index 79286120..b2b8394e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php
@@ -22,11 +22,6 @@ class ImSubTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSUB
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php
index 8abc3638..872c73c8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php
@@ -22,11 +22,6 @@ class ImSumTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMSUM
      *
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php
index 57b23815..9bf6b66c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php
@@ -22,11 +22,6 @@ class ImTanTest extends TestCase
         $this->complexAssert = new ComplexAssert();
     }
 
-    protected function tearDown(): void
-    {
-        $this->complexAssert = null;
-    }
-
     /**
      * @dataProvider providerIMTAN
      *
diff --git a/tests/PhpSpreadsheetTests/SettingsTest.php b/tests/PhpSpreadsheetTests/SettingsTest.php
index 92f3bb1f..7641f3da 100644
--- a/tests/PhpSpreadsheetTests/SettingsTest.php
+++ b/tests/PhpSpreadsheetTests/SettingsTest.php
@@ -8,7 +8,7 @@ use PHPUnit\Framework\TestCase;
 class SettingsTest extends TestCase
 {
     /**
-     * @var string
+     * @var bool
      */
     protected $prevValue;