Stubs and generated arginfo: remove tentative returns from final methods (#16213)

A tentative return type is used to allow userland code that overrides a method
to not include a typehint without a fatal error; this is inapplicable to final
methods (including all methods of final classes), which cannot be overridden.
Remove the tentative return declarations, and update the build script to
complain about future additions.

Author: DanielEScherzer

build/gen_stub.php

@@ -1291,6 +1291,9 @@ public function __construct(
         $this->attributes = $attributes;
         $this->framelessFunctionInfos = $framelessFunctionInfos;
         $this->exposedDocComment = $exposedDocComment;
+        if ($return->tentativeReturnType && $this->isFinalMethod()) {
+            throw new Exception("Tentative return inapplicable for final method");
+        }
     }
 
     public function isMethod(): bool

ext/reflection/php_reflection.stub.php

@@ -146,22 +146,16 @@ final class ReflectionGenerator
 {
     public function __construct(Generator $generator) {}
 
-    /** @tentative-return-type */
     public function getExecutingLine(): int {}
 
-    /** @tentative-return-type */
     public function getExecutingFile(): string {}
 
-    /** @tentative-return-type */
     public function getTrace(int $options = DEBUG_BACKTRACE_PROVIDE_OBJECT): array {}
 
-    /** @tentative-return-type */
     public function getFunction(): ReflectionFunctionAbstract {}
 
-    /** @tentative-return-type */
     public function getThis(): ?object {}
 
-    /** @tentative-return-type */
     public function getExecutingGenerator(): Generator {}
 
     public function isClosed(): bool {}

ext/reflection/php_reflection_arginfo.h

@@ -97,9 +97,6 @@ public function __toString(): string {}
     /** @tentative-return-type */
     public function __debugInfo(): array {}
 
-    /**
-     * @tentative-return-type
-     */
     #[\Deprecated(since: '8.2')]
     final public function _bad_state_ex(): void {}
 }