Add ExprUsedAsStringNode virtual node emitted when expressions are used as strings

src/Analyser/ExprHandler/AssignOpHandler.php

@@ -18,6 +18,7 @@
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\NodeScopeResolver;
 use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Node\ExprUsedAsStringNode;
 use PHPStan\Reflection\InitializerExprTypeResolver;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\Type\Constant\ConstantIntegerType;
@@ -99,6 +100,8 @@ static function (MutatingScope $scope) use ($stmt, $expr, $nodeCallback, $contex
 			$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($expr->expr, $scope);
 			$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
 			$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
+
+			$nodeScopeResolver->callNodeCallback($nodeCallback, new ExprUsedAsStringNode($expr->expr, $expr), $scope, $storage);
 		}
 
 		return new ExpressionResult(

src/Analyser/ExprHandler/CastStringHandler.php

@@ -13,6 +13,7 @@
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\NodeScopeResolver;
 use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Node\ExprUsedAsStringNode;
 use PHPStan\Reflection\InitializerExprTypeResolver;
 use PHPStan\Type\Type;
 use function array_merge;
@@ -46,6 +47,8 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
 		$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
 		$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
 
+		$nodeScopeResolver->callNodeCallback($nodeCallback, new ExprUsedAsStringNode($expr->expr, $expr), $scope, $storage);
+
 		$scope = $exprResult->getScope();
 
 		return new ExpressionResult(

src/Analyser/ExprHandler/InterpolatedStringHandler.php

@@ -14,6 +14,7 @@
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\NodeScopeResolver;
 use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Node\ExprUsedAsStringNode;
 use PHPStan\Reflection\InitializerExprTypeResolver;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\Type;
@@ -61,6 +62,8 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
 			$scope = $partResult->getScope();
 		}
 
+		$nodeScopeResolver->callNodeCallback($nodeCallback, new ExprUsedAsStringNode($expr, $expr), $scope, $storage);
+
 		return new ExpressionResult(
 			$scope,
 			hasYield: $hasYield,

src/Analyser/ExprHandler/PrintHandler.php

@@ -14,6 +14,7 @@
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\NodeScopeResolver;
 use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Node\ExprUsedAsStringNode;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Type;
 use function array_merge;
@@ -51,6 +52,8 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
 		$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
 		$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
 
+		$nodeScopeResolver->callNodeCallback($nodeCallback, new ExprUsedAsStringNode($expr->expr, $expr), $scope, $storage);
+
 		$scope = $exprResult->getScope();
 
 		return new ExpressionResult(

src/Analyser/NodeScopeResolver.php

@@ -85,6 +85,7 @@
 use PHPStan\Node\Expr\PropertyInitializationExpr;
 use PHPStan\Node\Expr\TypeExpr;
 use PHPStan\Node\Expr\UnsetOffsetExpr;
+use PHPStan\Node\ExprUsedAsStringNode;
 use PHPStan\Node\FinallyExitPointsNode;
 use PHPStan\Node\FunctionCallableNode;
 use PHPStan\Node\FunctionReturnStatementsNode;
@@ -996,6 +997,7 @@ public function processStmtNode(
 				$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($echoExpr, $scope);
 				$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
 				$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
+				$this->callNodeCallback($nodeCallback, new ExprUsedAsStringNode($echoExpr, $stmt), $scope, $storage);
 				$scope = $result->getScope();
 				$hasYield = $hasYield || $result->hasYield();
 				$isAlwaysTerminating = $isAlwaysTerminating || $result->isAlwaysTerminating();
@@ -2402,6 +2404,7 @@ public function leaveNode(Node $node): ?ExistingArrayDimFetch
 			$impurePoints = [
 				new ImpurePoint($scope, $stmt, 'betweenPhpTags', 'output between PHP opening and closing tags', true),
 			];
+			$this->callNodeCallback($nodeCallback, new ExprUsedAsStringNode(new TypeExpr(new ConstantStringType($stmt->value)), $stmt), $scope, $storage);
 		} elseif ($stmt instanceof Node\Stmt\Block) {
 			$result = $this->processStmtNodesInternal($stmt, $stmt->stmts, $scope, $storage, $nodeCallback, $context);
 			if ($this->polluteScopeWithBlock) {

src/Node/ExprUsedAsStringNode.php

@@ -0,0 +1,46 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Node;
+
+use Override;
+use PhpParser\Node;
+use PhpParser\Node\Expr;
+use PhpParser\NodeAbstract;
+
+/**
+ * @api
+ */
+final class ExprUsedAsStringNode extends NodeAbstract implements VirtualNode
+{
+
+	public function __construct(private Expr $expression, private Expr|Node\Stmt $originalNode)
+	{
+		parent::__construct($originalNode->getAttributes());
+	}
+
+	public function getExpression(): Expr
+	{
+		return $this->expression;
+	}
+
+	public function getOriginalNode(): Expr|Node\Stmt
+	{
+		return $this->originalNode;
+	}
+
+	#[Override]
+	public function getType(): string
+	{
+		return 'PHPStan_Node_ExprUsedAsStringNode';
+	}
+
+	/**
+	 * @return string[]
+	 */
+	#[Override]
+	public function getSubNodeNames(): array
+	{
+		return [];
+	}
+
+}

tests/PHPStan/Rules/ExprUsedAsString/ExprUsedAsStringRuleTest.php

@@ -0,0 +1,71 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\ExprUsedAsString;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<ExprUsedAsStringTestRule>
+ */
+class ExprUsedAsStringRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new ExprUsedAsStringTestRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/expr-used-as-string.php'], [
+			[
+				'Expression used as string: PhpParser\Node\Scalar\String_ in PhpParser\Node\Stmt\Echo_',
+				8,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Scalar\String_ in PhpParser\Node\Stmt\Echo_',
+				9,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Scalar\String_ in PhpParser\Node\Stmt\Echo_',
+				9,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Scalar\String_ in PhpParser\Node\Expr\Print_',
+				13,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Expr\Variable in PhpParser\Node\Expr\Cast\String_',
+				17,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Scalar\InterpolatedString in PhpParser\Node\Scalar\InterpolatedString',
+				26,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Expr\Variable in PhpParser\Node\Expr\AssignOp\Concat',
+				30,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Expr\BinaryOp\Concat in PhpParser\Node\Stmt\Echo_',
+				36,
+			],
+			[
+				'Expression used as string: PhpParser\Node\Scalar\InterpolatedString in PhpParser\Node\Scalar\InterpolatedString',
+				41,
+			],
+		]);
+	}
+
+	public function testInlineHtml(): void
+	{
+		$this->analyse([__DIR__ . '/data/inline-html.php'], [
+			[
+				'Expression used as string: PHPStan\Node\Expr\TypeExpr in PhpParser\Node\Stmt\InlineHTML',
+				7,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/ExprUsedAsString/ExprUsedAsStringTestRule.php

@@ -0,0 +1,35 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\ExprUsedAsString;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\ExprUsedAsStringNode;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use function get_class;
+
+/**
+ * @implements Rule<ExprUsedAsStringNode>
+ */
+class ExprUsedAsStringTestRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return ExprUsedAsStringNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$expr = $node->getExpression();
+		$originalNode = $node->getOriginalNode();
+
+		return [
+			RuleErrorBuilder::message('Expression used as string: ' . get_class($expr) . ' in ' . get_class($originalNode))
+				->identifier('tests.exprUsedAsString')
+				->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/ExprUsedAsString/data/expr-used-as-string.php

@@ -0,0 +1,44 @@
+<?php // lint >= 8.0
+
+namespace ExprUsedAsString;
+
+class Foo {
+
+	public function doEcho(): void {
+		echo 'hello';
+		echo 'hello', ' world';
+	}
+
+	public function doPrint(): void {
+		print 'hello';
+	}
+
+	public function doCast(int $i): void {
+		(string) $i;
+	}
+
+	public function doConcat(string $a, string $b): void {
+		$a . $b;
+		'a' . $b . 'c';
+	}
+
+	public function doInterpolatedString(string $name): void {
+		"Hello $name!";
+	}
+
+	public function doConcatAssign(string $a, string $b): void {
+		$a .= $b;
+	}
+
+}
+
+function doEchoConcat(string $s): void {
+	echo '<script src="' . $s . '" nonce=123></script>';
+}
+
+function doHeredoc(): void {
+	$nonce = '123';
+	$html = <<<EOS
+	<script nonce="{$nonce}" type="module">
+	EOS;
+}

tests/PHPStan/Rules/ExprUsedAsString/data/inline-html.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace ExprUsedAsStringInlineHtml;
+
+function doFoo(): void {
+?>
+<script src="my.js" nonce=123></script>
+<?php
+}