Add implicit throw point for dynamic instantiation of non-final classes without constructors

- In `NewHandler::processExpr`, when a dynamic class name (`new $class()`) resolves
  to a single non-final class without a constructor, add an implicit throw point and
  an uncertain impure point. This is because the actual runtime class could be a
  subclass with a constructor that throws.
- The fix is guarded by `implicitThrows` to remain consistent with how constructors
  are handled when that setting is disabled.
- Fixes the false positive "Dead catch" for `class-string<Interface>`,
  `class-string<AbstractClass>`, and `class-string<NonFinalClass>` where the
  referenced type has no constructor.
- Also fixes the false positive "Function returns void but does not have any side
  effects" for the same scenarios.
- Updated `bug-4806` test which was asserting the buggy behavior for a non-final
  class without a constructor.

Author: VincentLanglet

src/Analyser/ExprHandler/NewHandler.php

@@ -184,6 +184,17 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
 				);
 			}
 
+			if ($classReflection !== null && $constructorReflection === null && !$classReflection->isFinal() && $this->implicitThrows) {
+				$throwPoints[] = InternalThrowPoint::createImplicit($scope, $expr);
+				$impurePoints[] = new ImpurePoint(
+					$scope,
+					$expr,
+					'new',
+					sprintf('instantiation of class %s', $classReflection->getDisplayName()),
+					false,
+				);
+			}
+
 			if ($parametersAcceptor !== null) {
 				$normalizedExpr = ArgumentsNormalizer::reorderNewArguments($parametersAcceptor, $expr) ?? $expr;
 			}

tests/PHPStan/Rules/Exceptions/CatchWithUnthrownExceptionRuleTest.php

@@ -273,10 +273,6 @@ public function testBug4806(): void
 				'Dead catch - ArgumentCountError is never thrown in the try block.',
 				65,
 			],
-			[
-				'Dead catch - Throwable is never thrown in the try block.',
-				119,
-			],
 		]);
 	}
 
@@ -798,4 +794,14 @@ public function testBug14569(): void
 		$this->analyse([__DIR__ . '/data/bug-14569.php'], []);
 	}
 
+	public function testBug6574(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-6574.php'], [
+			[
+				'Dead catch - Exception is never thrown in the try block.',
+				83,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Exceptions/data/bug-6574.php

@@ -0,0 +1,85 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6574;
+
+interface FooInterface
+{
+}
+
+interface BarInterface
+{
+	public function __construct();
+}
+
+abstract class AbstractBaz
+{
+}
+
+abstract class AbstractQux
+{
+	public function __construct()
+	{
+	}
+}
+
+class NonFinalClass
+{
+}
+
+final class FinalClass
+{
+}
+
+/** @param class-string<FooInterface> $class */
+function interfaceWithoutConstructor(string $class): void
+{
+	try {
+		new $class();
+	} catch (\Exception $e) {
+	}
+}
+
+/** @param class-string<BarInterface> $class */
+function interfaceWithConstructor(string $class): void
+{
+	try {
+		new $class();
+	} catch (\Exception $e) {
+	}
+}
+
+/** @param class-string<AbstractBaz> $class */
+function abstractClassWithoutConstructor(string $class): void
+{
+	try {
+		new $class();
+	} catch (\Exception $e) {
+	}
+}
+
+/** @param class-string<AbstractQux> $class */
+function abstractClassWithConstructor(string $class): void
+{
+	try {
+		new $class();
+	} catch (\Exception $e) {
+	}
+}
+
+/** @param class-string<NonFinalClass> $class */
+function nonFinalClassWithoutConstructor(string $class): void
+{
+	try {
+		new $class();
+	} catch (\Exception $e) {
+	}
+}
+
+/** @param class-string<FinalClass> $class */
+function finalClassWithoutConstructor(string $class): void
+{
+	try {
+		new $class();
+	} catch (\Exception $e) { // dead catch - final class with no constructor
+	}
+}

tests/PHPStan/Rules/Pure/PureFunctionRuleTest.php

@@ -225,4 +225,9 @@ public function testBug14557(): void
 		$this->analyse([__DIR__ . '/data/bug-14557-function.php'], []);
 	}
 
+	public function testBug6574(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-6574.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Pure/data/bug-6574.php

@@ -0,0 +1,23 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6574Pure;
+
+interface FooInterface
+{
+}
+
+abstract class AbstractBar
+{
+}
+
+/** @param class-string<FooInterface> $class */
+function interfaceWithoutConstructor(string $class): void
+{
+	new $class();
+}
+
+/** @param class-string<AbstractBar> $class */
+function abstractClassWithoutConstructor(string $class): void
+{
+	new $class();
+}