diff --git a/phpstan.neon b/phpstan.neon
index 7d7f95975..a95f15d28 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,5 +1,5 @@
 parameters:
-    level: 5
+    level: 6
     paths:
         - src
         - tests/tests
diff --git a/src/Data/ProcessedCodeCoverageData.php b/src/Data/ProcessedCodeCoverageData.php
index 57ccbb166..70f2d811c 100644
--- a/src/Data/ProcessedCodeCoverageData.php
+++ b/src/Data/ProcessedCodeCoverageData.php
@@ -41,7 +41,10 @@
  *      }>,
  *      hit: list<TestIdType>
  *  }
- * @phpstan-type FunctionCoverageType array<string, array<string, FunctionCoverageDataType>>
+ * @phpstan-type FunctionCoverageForFileType array<string, FunctionCoverageDataType>
+ * @phpstan-type FunctionCoverageType array<string, FunctionCoverageForFileType>
+ * @phpstan-type LineCoverageForFileType array<int, null|list<TestIdType>>
+ * @phpstan-type LineCoverageType array<string, LineCoverageForFileType>
  */
 final class ProcessedCodeCoverageData
 {
@@ -49,7 +52,7 @@ final class ProcessedCodeCoverageData
      * Line coverage data.
      * An array of filenames, each having an array of linenumbers, each executable line having an array of testcase ids.
      *
-     * @var array<string, array<int, null|list<TestIdType>>>
+     * @var LineCoverageType
      */
     private array $lineCoverage = [];
 
@@ -112,11 +115,17 @@ public function markCodeAsExecutedByTestCase(string $testCaseId, RawCodeCoverage
         }
     }
 
+    /**
+     * @param LineCoverageType $lineCoverage
+     */
     public function setLineCoverage(array $lineCoverage): void
     {
         $this->lineCoverage = $lineCoverage;
     }
 
+    /**
+     * @return LineCoverageType
+     */
     public function lineCoverage(): array
     {
         ksort($this->lineCoverage);
@@ -124,11 +133,17 @@ public function lineCoverage(): array
         return $this->lineCoverage;
     }
 
+    /**
+     * @param FunctionCoverageType $functionCoverage
+     */
     public function setFunctionCoverage(array $functionCoverage): void
     {
         $this->functionCoverage = $functionCoverage;
     }
 
+    /**
+     * @return FunctionCoverageType
+     */
     public function functionCoverage(): array
     {
         ksort($this->functionCoverage);
@@ -136,6 +151,9 @@ public function functionCoverage(): array
         return $this->functionCoverage;
     }
 
+    /**
+     * @return list<non-empty-string>
+     */
     public function coveredFiles(): array
     {
         ksort($this->lineCoverage);
@@ -220,6 +238,8 @@ public function merge(self $newData): void
      *
      * During a merge, a higher number is better.
      *
+     * @param LineCoverageForFileType $data
+     *
      * @return 1|2|3|4
      */
     private function priorityForLine(array $data, int $line): int
diff --git a/src/Node/Builder.php b/src/Node/Builder.php
index e6b83f999..90454dec8 100644
--- a/src/Node/Builder.php
+++ b/src/Node/Builder.php
@@ -29,6 +29,8 @@
  * @internal This class is not covered by the backward compatibility promise for phpunit/php-code-coverage
  *
  * @phpstan-import-type TestType from CodeCoverage
+ * @phpstan-import-type FunctionCoverageForFileType from ProcessedCodeCoverageData
+ * @phpstan-import-type LineCoverageForFileType from ProcessedCodeCoverageData
  */
 final readonly class Builder
 {
@@ -132,7 +134,7 @@ private function addItems(Directory $root, array $items, array $tests): void
      * )
      * </code>
      *
-     * @return array<string, array<string, array{lineCoverage: array<int, int>, functionCoverage: array<string, array<int, int>>}>>
+     * @return array<string, array{lineCoverage: LineCoverageForFileType, functionCoverage: FunctionCoverageForFileType}>
      */
     private function buildDirectoryStructure(ProcessedCodeCoverageData $data): array
     {
diff --git a/src/Report/Html/Renderer/File.php b/src/Report/Html/Renderer/File.php
index 09dbe31fe..b1c3f7e97 100644
--- a/src/Report/Html/Renderer/File.php
+++ b/src/Report/Html/Renderer/File.php
@@ -102,6 +102,7 @@
 use function str_replace;
 use function token_get_all;
 use function trim;
+use SebastianBergmann\CodeCoverage\CodeCoverage;
 use SebastianBergmann\CodeCoverage\FileCouldNotBeWrittenException;
 use SebastianBergmann\CodeCoverage\Node\File as FileNode;
 use SebastianBergmann\CodeCoverage\Util\Percentage;
@@ -113,6 +114,7 @@
  * @phpstan-import-type ProcessedTraitType from FileNode
  * @phpstan-import-type ProcessedMethodType from FileNode
  * @phpstan-import-type ProcessedFunctionType from FileNode
+ * @phpstan-import-type TestType from CodeCoverage
  *
  * @internal This class is not covered by the backward compatibility promise for phpunit/php-code-coverage
  */
@@ -906,7 +908,8 @@ private function renderPathStructure(FileNode $node): string
     }
 
     /**
-     * @param list<string> $codeLines
+     * @param list<string>            $codeLines
+     * @param array<string, TestType> $testData
      */
     private function renderPathLines(array $path, array $branches, array $codeLines, array $testData): string
     {
@@ -1118,6 +1121,9 @@ private function abbreviateMethodName(string $methodName): string
         return $methodName;
     }
 
+    /**
+     * @param TestType $testData
+     */
     private function createPopoverContentForTest(string $test, array $testData): string
     {
         $testCSS = '';
diff --git a/src/Target/MapBuilder.php b/src/Target/MapBuilder.php
index 11a8088ff..cfda06293 100644
--- a/src/Target/MapBuilder.php
+++ b/src/Target/MapBuilder.php
@@ -206,6 +206,10 @@ public function build(Filter $filter, FileAnalyser $analyser): array
         ];
     }
 
+    /**
+     * @param TargetMapPart                             $methods
+     * @param array<non-empty-string, non-empty-string> $reverseLookup
+     */
     private function processMethods(Class_|Trait_ $classOrTrait, string $file, array &$methods, array &$reverseLookup): void
     {
         foreach ($classOrTrait->methods() as $method) {
diff --git a/tests/tests/Target/MapBuilderTest.php b/tests/tests/Target/MapBuilderTest.php
index dbdaef30d..de1612653 100644
--- a/tests/tests/Target/MapBuilderTest.php
+++ b/tests/tests/Target/MapBuilderTest.php
@@ -417,6 +417,10 @@ public static function provider(): array
         ];
     }
 
+    /**
+     * @param TargetMap                        $expected
+     * @param non-empty-list<non-empty-string> $files
+     */
     #[DataProvider('provider')]
     public function testBuildsMap(array $expected, array $files): void
     {