Fix CS, PHPStan, and test failures

- Add missing `use function assert;` import in MutatingScope.php
- Add @template generic type annotations to PossiblyImpureTipHelper::addTip()
- Update ElseIfConstantConditionRuleTest::testBug6947 expected tip to include
  possibly-impure tip alongside treatPhpDocTypesAsCertain tip
- Fix native-types-81.php: closures with `: string` return type now correctly
  resolve to native type `string` instead of `non-empty-string` (the previous
  `non-empty-string` was due to a closure type cache key collision between
  regular and native-promoted scopes)

Co-authored-by: Ondřej Mirtes <ondrejmirtes@users.noreply.github.com>

Author: phpstan-bot

src/Analyser/MutatingScope.php

@@ -145,6 +145,7 @@
 use Throwable;
 use ValueError;
 use function abs;
+use function assert;
 use function array_filter;
 use function array_key_exists;
 use function array_key_first;

src/Rules/Comparison/PossiblyImpureTipHelper.php

@@ -7,6 +7,7 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\AutowiredParameter;
 use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Rules\RuleError;
 use PHPStan\Rules\RuleErrorBuilder;
 use function count;
 
@@ -21,6 +22,11 @@ public function __construct(
 	{
 	}
 
+	/**
+	 * @template T of RuleError
+	 * @param RuleErrorBuilder<T> $ruleErrorBuilder
+	 * @return RuleErrorBuilder<T>
+	 */
 	public function addTip(
 		Scope $scope,
 		Expr $conditionExpr,

tests/PHPStan/Analyser/nsrt/native-types-81.php

@@ -25,12 +25,12 @@ public function doFoo(): void
 		};
 
 		assertType('non-empty-string', $f());
-		assertNativeType('non-empty-string', $f());
+		assertNativeType('string', $f());
 
 		assertType('non-empty-string', (function (): string {
 			return funcWithANativeReturnType();
 		})());
-		assertNativeType('non-empty-string', (function (): string {
+		assertNativeType('string', (function (): string {
 			return funcWithANativeReturnType();
 		})());
 

tests/PHPStan/Rules/Comparison/ElseIfConstantConditionRuleTest.php

@@ -147,7 +147,7 @@ public function testBug6947(): void
 			[
 				'Elseif condition is always false.',
 				13,
-				'Because the type is coming from a PHPDoc, you can turn off this check by setting <fg=cyan>treatPhpDocTypesAsCertain: false</> in your <fg=cyan>%configurationFile%</>.',
+				"• Because the type is coming from a PHPDoc, you can turn off this check by setting <fg=cyan>treatPhpDocTypesAsCertain: false</> in your <fg=cyan>%configurationFile%</>.\n• If Bug6947\HelloWorld::getValue() is impure, add <fg=cyan>@phpstan-impure</> PHPDoc tag above its declaration.",
 			],
 		]);
 	}