✨ Add generics templating

docs/src/content/en/docs/getting-started/changelog.md

@@ -17,6 +17,7 @@ toc: true
 
 - Upgrade to Symfony 6.3
 - Refactor docs structure
+- Add generics templating from https://gpb.moe/doc/slides/Gestion_Erreur_Toutes_Ses_Couleurs_FR.pdf
 
 ### 1.1.2
 

examples/generic-errors.php

@@ -0,0 +1,89 @@
+<?php
+
+declare(strict_types=1);
+
+require __DIR__.'/../vendor/autoload.php';
+
+// https://gpb.moe/doc/slides/Gestion_Erreur_Toutes_Ses_Couleurs_FR.pdf
+// https://psalm.dev/r/dd8e8f59fe
+
+/**
+ * @template T1
+ * @template E1
+ */
+class Wrapper {
+    /**
+     * @param T1 $value
+     * @param E1 $err
+     */
+      public function __construct(
+          public mixed $value,
+          public mixed $err,
+          public bool $isErr = false, 
+      ) {}
+
+    /**
+     * @template T2
+     * @template E2
+     * @param callable(T1): Wrapper<T2, E2> $f
+     * @return Wrapper<T2, E1|E2>
+     */
+    public function bind($f): Wrapper {
+      if ($this->isErr) {
+          /** @var Wrapper<T2, E1> Shut up Psalm */
+          return $this;
+      }
+      return $f($this->value);
+    }
+  }
+
+  enum OpenFileErrors {
+      case FileDoesNotExist;
+      case AccessDenied;
+      case IsDirectory;
+  }
+
+  class File {}
+
+  enum GetContentErrors {
+      case E1;
+      case E2;
+  }
+
+  enum ParseContentErrors {
+      case E1;
+      case E2;
+  }
+
+  class UnparsedOutput {}
+  class ParsedOutput {}
+
+  /** @return Wrapper<File, OpenFileErrors> */
+  function open_file(string $path): Wrapper {
+      return new Wrapper(new File(), OpenFileErrors::FileDoesNotExist);
+  }
+
+  /** @return Wrapper<UnparsedOutput, GetContentErrors> */
+  function get_content_file(File $f): Wrapper {
+      return new Wrapper(new UnparsedOutput(), GetContentErrors::E1);
+  }
+  /** @return Wrapper<ParsedOutput, ParseContentErrors> */
+  function parse_content(UnparsedOutput $f): Wrapper {
+      return new Wrapper(new ParsedOutput(), ParseContentErrors::E1);
+  }
+
+  $data = open_file('')
+      ->bind(get_content_file(...))
+      ->bind(parse_content(...));
+  $result = match ($data->isErr) {
+      true => match ($data->err) {
+          OpenFileErrors::FileDoesNotExist => 1,
+          OpenFileErrors::AccessDenied => 2,
+          OpenFileErrors::IsDirectory => 3,
+          GetContentErrors::E1 => 4,
+          GetContentErrors::E2 => 5,
+          ParseContentErrors::E1 => 6,
+          ParseContentErrors::E2 => 7,
+      },
+      false => $data->value,
+  };