WIP: add option to prohibit coercing bool to string

Author: schlndh

conf/bleedingEdge.neon

@@ -34,3 +34,4 @@ parameters:
 		unusedVariable: true
 		unusedParameters: true
 		reuseCollectedDataRuleErrors: true
+		checkTypeCoercions: true

conf/config.neon

@@ -66,6 +66,7 @@ parameters:
 		unusedVariable: false
 		unusedParameters: false
 		reuseCollectedDataRuleErrors: false
+		checkTypeCoercions: false
 	fileExtensions:
 		- php
 	checkAdvancedIsset: false
@@ -267,6 +268,8 @@ parameters:
 		- [parameters, tmpDir]
 		- [parameters, pro]
 		- parametersSchema
+	allowedTypeCoercions:
+		boolToString: true
 
 autowiredAttributeServices:
 	level: null

conf/parametersSchema.neon

@@ -63,6 +63,7 @@ parametersSchema:
 		unusedVariable: bool()
 		unusedParameters: bool()
 		reuseCollectedDataRuleErrors: bool()
+		checkTypeCoercions: bool()
 	])
 	fileExtensions: listOf(string())
 	checkAdvancedIsset: bool()
@@ -199,6 +200,9 @@ parametersSchema:
 		string(),
 		listOf(string()),
 	)))
+	allowedTypeCoercions: structure([
+		boolToString: bool()
+	])
 
 	# playground mode
 	sourceLocatorPlaygroundMode: bool()

src/Rules/Cast/InvalidPartOfEncapsedStringRule.php

@@ -9,6 +9,7 @@
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Rules\RuleLevelHelper;
+use PHPStan\Rules\TypeCoercionRuleHelper;
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\Type;
 use PHPStan\Type\VerbosityLevel;
@@ -24,6 +25,7 @@ final class InvalidPartOfEncapsedStringRule implements Rule
 	public function __construct(
 		private ExprPrinter $exprPrinter,
 		private RuleLevelHelper $ruleLevelHelper,
+		private TypeCoercionRuleHelper $typeCoercionRuleHelper,
 	)
 	{
 	}
@@ -45,14 +47,14 @@ public function processNode(Node $node, Scope $scope): array
 				$scope,
 				$part,
 				'',
-				static fn (Type $type): bool => !$type->toString() instanceof ErrorType,
+				fn (Type $type): bool => !$this->typeCoercionRuleHelper->coerceToString($type) instanceof ErrorType,
 			);
 			$partType = $typeResult->getType();
 			if ($partType instanceof ErrorType) {
 				continue;
 			}
 
-			$stringPartType = $partType->toString();
+			$stringPartType = $this->typeCoercionRuleHelper->coerceToString($partType);
 			if (!$stringPartType instanceof ErrorType) {
 				continue;
 			}

src/Rules/TypeCoercionRuleHelper.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules;
+
+use PHPStan\DependencyInjection\AutowiredParameter;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Type\ErrorType;
+use PHPStan\Type\Type;
+
+#[AutowiredService]
+final class TypeCoercionRuleHelper
+{
+
+	public function __construct(
+		#[AutowiredParameter(ref: '%featureToggles.checkTypeCoercions%')]
+		private readonly bool $checkTypeCoercions,
+		#[AutowiredParameter(ref: '%allowedTypeCoercions.boolToString%')]
+		private readonly bool $allowBoolToString,
+	)
+	{
+	}
+
+	public function coerceToString(Type $type): Type
+	{
+		if (!$this->checkTypeCoercions) {
+			return $type->toString();
+		}
+		if (!$this->allowBoolToString && !$type->isBoolean()->no()) {
+			return new ErrorType();
+		}
+		return $type->toString();
+	}
+
+}

tests/PHPStan/Rules/Cast/InvalidPartOfEncapsedStringRuleTest.php

@@ -6,6 +6,7 @@
 use PHPStan\Node\Printer\Printer;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleLevelHelper;
+use PHPStan\Rules\TypeCoercionRuleHelper;
 use PHPStan\Testing\RuleTestCase;
 use PHPUnit\Framework\Attributes\RequiresPhp;
 
@@ -15,6 +16,8 @@
 class InvalidPartOfEncapsedStringRuleTest extends RuleTestCase
 {
 
+	private ?TypeCoercionRuleHelper $typeCoercionRuleHelper = null;
+
 	protected function getRule(): Rule
 	{
 		return new InvalidPartOfEncapsedStringRule(
@@ -29,6 +32,7 @@ protected function getRule(): Rule
 				checkBenevolentUnionTypes: false,
 				discoveringSymbolsTip: true,
 			),
+			$this->typeCoercionRuleHelper ?? new TypeCoercionRuleHelper(true, true),
 		);
 	}
 
@@ -54,6 +58,37 @@ public function testRule(): void
 		]);
 	}
 
+	public function testRuleWithStrictCoercions(): void
+	{
+		$this->typeCoercionRuleHelper = new TypeCoercionRuleHelper(true, false);
+		$this->analyse([__DIR__ . '/data/invalid-encapsed-part.php'], [
+			[
+				'Part $std (stdClass) of encapsed string cannot be cast to string.',
+				26,
+			],
+			[
+				'Part $bool (bool) of encapsed string cannot be cast to string.',
+				27,
+			],
+			[
+				'Part $array (array) of encapsed string cannot be cast to string.',
+				30,
+			],
+			[
+				'Part $std (stdClass|string) of encapsed string cannot be cast to string.',
+				56,
+			],
+			[
+				'Part $bool (bool|string) of encapsed string cannot be cast to string.',
+				57,
+			],
+			[
+				'Part $array (array|string) of encapsed string cannot be cast to string.',
+				60,
+			],
+		]);
+	}
+
 	#[RequiresPhp('>= 8.0.0')]
 	public function testRuleWithNullsafeVariant(): void
 	{