Initial support for assignment in condition

src/Analyser/TypeSpecifier.php

@@ -135,6 +135,9 @@ public function specifyTypesInCondition(
 			if ($expressions !== null) {
 				/** @var Expr $exprNode */
 				$exprNode = $expressions[0];
+				if ($exprNode instanceof Expr\Assign) {
+					$exprNode = $exprNode->var;
+				}
 				/** @var \PHPStan\Type\ConstantScalarType $constantType */
 				$constantType = $expressions[1];
 				if ($constantType->getValue() === false) {

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -8803,6 +8803,33 @@ public function testUnionProperties(
 		);
 	}
 
+	public function dataAssignmentInCondition(): array
+	{
+		return [
+			[
+				'AssignmentInCondition\Foo',
+				'$bar',
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataAssignmentInCondition
+	 * @param string $description
+	 * @param string $expression
+	 */
+	public function testAssignmentInCondition(
+		string $description,
+		string $expression
+	): void
+	{
+		$this->assertTypes(
+			__DIR__ . '/data/assignment-in-condition.php',
+			$description,
+			$expression
+		);
+	}
+
 	private function assertTypes(
 		string $file,
 		string $description,

tests/PHPStan/Analyser/TypeSpecifierTest.php

@@ -6,6 +6,7 @@
 use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\BinaryOp\Equal;
 use PhpParser\Node\Expr\BinaryOp\Identical;
+use PhpParser\Node\Expr\BinaryOp\NotIdentical;
 use PhpParser\Node\Expr\BooleanNot;
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\PropertyFetch;
@@ -46,6 +47,7 @@ protected function setUp(): void
 		$this->scope = $this->scope->assignVariable('bar', new ObjectType('Bar'));
 		$this->scope = $this->scope->assignVariable('stringOrNull', new UnionType([new StringType(), new NullType()]));
 		$this->scope = $this->scope->assignVariable('barOrNull', new UnionType([new ObjectType('Bar'), new NullType()]));
+		$this->scope = $this->scope->assignVariable('barOrFalse', new UnionType([new ObjectType('Bar'), new ConstantBooleanType(false)]));
 		$this->scope = $this->scope->assignVariable('stringOrFalse', new UnionType([new StringType(), new ConstantBooleanType(false)]));
 		$this->scope = $this->scope->assignVariable('array', new ArrayType(new MixedType(), new MixedType()));
 		$this->scope = $this->scope->assignVariable('foo', new MixedType());
@@ -631,6 +633,114 @@ public function dataCondition(): array
 					'isset(Foo::$bar)' => '~object|nonEmpty',
 				],
 			],
+			[
+				new Identical(
+					new Variable('barOrNull'),
+					new Expr\ConstFetch(new Name('null'))
+				),
+				[
+					'$barOrNull' => 'null',
+				],
+				[
+					'$barOrNull' => '~null',
+				],
+			],
+			[
+				new Identical(
+					new Expr\Assign(
+						new Variable('notNullBar'),
+						new Variable('barOrNull')
+					),
+					new Expr\ConstFetch(new Name('null'))
+				),
+				[
+					'$notNullBar' => 'null',
+				],
+				[
+					'$notNullBar' => '~null',
+				],
+			],
+			[
+				new NotIdentical(
+					new Variable('barOrNull'),
+					new Expr\ConstFetch(new Name('null'))
+				),
+				[
+					'$barOrNull' => '~null',
+				],
+				[
+					'$barOrNull' => 'null',
+				],
+			],
+			[
+				new NotIdentical(
+					new Expr\Assign(
+						new Variable('notNullBar'),
+						new Variable('barOrNull')
+					),
+					new Expr\ConstFetch(new Name('null'))
+				),
+				[
+					'$notNullBar' => '~null',
+				],
+				[
+					'$notNullBar' => 'null',
+				],
+			],
+			[
+				new Identical(
+					new Variable('barOrFalse'),
+					new Expr\ConstFetch(new Name('false'))
+				),
+				[
+					'$barOrFalse' => 'false & ~object|nonEmpty',
+				],
+				[
+					'$barOrFalse' => '~false',
+				],
+			],
+			[
+				new Identical(
+					new Expr\Assign(
+						new Variable('notFalseBar'),
+						new Variable('barOrFalse')
+					),
+					new Expr\ConstFetch(new Name('false'))
+				),
+				[
+					'$notFalseBar' => 'false & ~object|nonEmpty',
+				],
+				[
+					'$notFalseBar' => '~false',
+				],
+			],
+			[
+				new NotIdentical(
+					new Variable('barOrFalse'),
+					new Expr\ConstFetch(new Name('false'))
+				),
+				[
+					'$barOrFalse' => '~false',
+				],
+				[
+					'$barOrFalse' => 'false & ~object|nonEmpty',
+				],
+			],
+			[
+				new NotIdentical(
+					new Expr\Assign(
+						new Variable('notFalseBar'),
+						new Variable('barOrFalse')
+					),
+					new Expr\ConstFetch(new Name('false'))
+				),
+				[
+					'$notFalseBar' => '~false',
+				],
+				[
+					'$notFalseBar' => 'false & ~object|nonEmpty',
+				],
+			],
 		];
 	}
 

tests/PHPStan/Analyser/data/assignment-in-condition.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace AssignmentInCondition;
+
+class Foo
+{
+
+	public function doFoo(): ?self
+	{
+
+	}
+
+	public function doBar()
+	{
+		$foo = new self();
+		if (null !== $bar = $foo->doFoo()) {
+			die;
+		}
+	}
+
+}