Check datetime instantiation

conf/bleedingEdge.neon

@@ -7,5 +7,6 @@ parameters:
 		fileWhitespace: true
 		unusedClassElements: true
 		readComposerPhpVersion: true
+		dateTimeInstantiation: true
 	stubFiles:
 		- ../stubs/SplObjectStorage.stub

conf/config.level5.neon

@@ -4,6 +4,8 @@ includes:
 conditionalTags:
 	PHPStan\Rules\Functions\RandomIntParametersRule:
 		phpstan.rules.rule: %featureToggles.randomIntParameters%
+	PHPStan\Rules\DateTimeInstantiationRule:
+		phpstan.rules.rule: %featureToggles.dateTimeInstantiation%
 
 parameters:
 	checkFunctionArgumentTypes: true
@@ -15,3 +17,5 @@ services:
 		class: PHPStan\Rules\Functions\RandomIntParametersRule
 		arguments:
 			reportMaybes: %reportMaybes%
+	-
+		class: PHPStan\Rules\DateTimeInstantiationRule

conf/config.neon

@@ -19,6 +19,7 @@ parameters:
 		fileWhitespace: false
 		unusedClassElements: false
 		readComposerPhpVersion: false
+		dateTimeInstantiation: false
 	fileExtensions:
 		- php
 	checkAlwaysTrueCheckTypeFunctionCall: false
@@ -151,6 +152,7 @@ parametersSchema:
 		fileWhitespace: bool(),
 		unusedClassElements: bool(),
 		readComposerPhpVersion: bool()
+		dateTimeInstantiation: bool()
 	])
 	fileExtensions: listOf(string())
 	checkAlwaysTrueCheckTypeFunctionCall: bool()

src/Rules/DateTimeInstantiationRule.php

@@ -0,0 +1,70 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules;
+
+use DateTime;
+use PhpParser\Node;
+use PhpParser\Node\Expr\New_;
+use PHPStan\Analyser\Scope;
+use PHPStan\Type\Constant\ConstantStringType;
+
+/**
+ * @implements \PHPStan\Rules\Rule<\PhpParser\Node\Expr\New_>
+ */
+class DateTimeInstantiationRule implements \PHPStan\Rules\Rule
+{
+
+	public function getNodeType(): string
+	{
+		return New_::class;
+	}
+
+	/**
+	 * @param New_ $node
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (
+			!($node->class instanceof \PhpParser\Node\Name)
+			|| \count($node->args) === 0
+			|| !\in_array(strtolower((string) $node->class), ['datetime', 'datetimeimmutable'], true)
+		) {
+			return [];
+		}
+
+		$arg = $scope->getType($node->args[0]->value);
+		if (!($arg instanceof ConstantStringType)) {
+			return [];
+		}
+
+		$errors = [];
+		$dateString = $arg->getValue();
+		try {
+			new DateTime($dateString);
+		} catch (\Throwable $e) {
+			// an exception is thrown for errors only but we want to catch warnings too
+		}
+		$lastErrors = DateTime::getLastErrors();
+		if ($lastErrors !== false) {
+			foreach ($lastErrors['warnings'] as $warning) {
+				$errors[] = RuleErrorBuilder::message(sprintf(
+					'Instantiating %s with %s produces a warning: %s',
+					(string) $node->class,
+					$dateString,
+					$warning
+				))->build();
+			}
+			foreach ($lastErrors['errors'] as $error) {
+				$errors[] = RuleErrorBuilder::message(sprintf(
+					'Instantiating %s with %s produces an error: %s',
+					(string) $node->class,
+					$dateString,
+					$error
+				))->build();
+			}
+		}
+
+		return $errors;
+	}
+
+}

tests/PHPStan/Rules/DateTimeInstantiationRuleTest.php

@@ -0,0 +1,49 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules;
+
+/**
+ * @extends \PHPStan\Testing\RuleTestCase<DateTimeInstantiationRule>
+ */
+class DateTimeInstantiationRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): \PHPStan\Rules\Rule
+	{
+		return new DateTimeInstantiationRule();
+	}
+
+	public function test(): void
+	{
+		$this->analyse(
+			[__DIR__ . '/data/datetime-instantiation.php'],
+			[
+				[
+					'Instantiating DateTime with 2020.11.17 produces an error: Double time specification',
+					3,
+				],
+				[
+					'Instantiating DateTimeImmutable with asdfasdf produces a warning: Double timezone specification',
+					5,
+				],
+				[
+					'Instantiating DateTimeImmutable with asdfasdf produces an error: The timezone could not be found in the database',
+					5,
+				],
+				[
+					'Instantiating DateTimeImmutable with 2020.11.17 produces an error: Double time specification',
+					10,
+				],
+				[
+					'Instantiating DateTimeImmutable with 2020.11.18 produces an error: Double time specification',
+					17,
+				],
+				[
+					'Instantiating DateTime with 2020-04-31 produces a warning: The parsed date was invalid',
+					20,
+				],
+			]
+		);
+	}
+
+}

tests/PHPStan/Rules/data/datetime-instantiation.php

@@ -0,0 +1,20 @@
+<?php
+
+new DateTime('2020.11.17');
+
+new DateTimeImmutable('asdfasdf');
+
+new DateTime('');
+
+$test = '2020.11.17';
+new DateTimeImmutable($test);
+
+/**
+ * @param '2020.11.18' $date2
+ */
+function foo(string $date, string $date2): void {
+	new DateTime($date);
+	new DateTimeImmutable($date2);
+}
+
+new DateTime('2020-04-31');