Fix false positive when type casting in IF statement

src/Analyser/TypeSpecifier.php

@@ -197,15 +197,31 @@ public function specifyTypesInCondition(
 				$context,
 				$rootExpr,
 			);
-		} elseif (
-			$expr instanceof Expr\Cast\String_
-			|| $expr instanceof Expr\Cast\Double
-			|| $expr instanceof Expr\Cast\Int_
-			|| $expr instanceof Expr\Cast\Bool_
-		) {
+		} elseif ($expr instanceof Expr\Cast\Bool_) {
+			return $this->specifyTypesInCondition(
+				$scope,
+				new Node\Expr\BinaryOp\Equal($expr->expr, new ConstFetch(new Name\FullyQualified('true'))),
+				$context,
+				$rootExpr,
+			);
+		} elseif ($expr instanceof Expr\Cast\String_) {
+			return $this->specifyTypesInCondition(
+				$scope,
+				new Node\Expr\BinaryOp\NotEqual($expr->expr, new Node\Scalar\String_('')),
+				$context,
+				$rootExpr,
+			);
+		} elseif ($expr instanceof Expr\Cast\Int_) {
+			return $this->specifyTypesInCondition(
+				$scope,
+				new Node\Expr\BinaryOp\NotEqual($expr->expr, new Node\Scalar\LNumber(0)),
+				$context,
+				$rootExpr,
+			);
+		} elseif ($expr instanceof Expr\Cast\Double) {
 			return $this->specifyTypesInCondition(
 				$scope,
-				new Node\Expr\BinaryOp\NotEqual($expr->expr, new ConstFetch(new Name\FullyQualified('false'))),
+				new Node\Expr\BinaryOp\NotEqual($expr->expr, new Node\Scalar\DNumber(0.0)),
 				$context,
 				$rootExpr,
 			);

tests/PHPStan/Analyser/nsrt/narrow-cast.php

@@ -31,9 +31,9 @@ function doFoo(string $x, array $arr): void {
 /** @param int<-5, 5> $x */
 function castString($x, string $s, bool $b) {
 	if ((string) $x) {
-		assertType('int<-5, -1>|int<1, 5>', $x);
+		assertType('int<-5, 5>', $x);
 	} else {
-		assertType('0', $x);
+		assertType('int<-5, 5>', $x);
 	}
 
 	if ((string) $b) {
@@ -63,8 +63,14 @@ function castInt($x, string $s, bool $b) {
         assertType('false', $b);
     }
 
+	if ((int) $s) {
+		assertType('string', $s);
+	} else {
+		assertType('string', $s);
+	}
+
     if ((int) strpos($s, 'xy')) {
-        assertType('non-falsy-string', $s);
+        assertType('string', $s);
     } else {
         assertType('string', $s);
     }
@@ -73,9 +79,9 @@ function castInt($x, string $s, bool $b) {
 /** @param int<-5, 5> $x */
 function castFloat($x, string $s, bool $b) {
     if ((float) $x) {
-        assertType('int<-5, -1>|int<1, 5>', $x);
+        assertType('int<-5, 5>', $x);
     } else {
-        assertType('0', $x);
+        assertType('int<-5, 5>', $x);
     }
 
     if ((float) $b) {
@@ -85,8 +91,8 @@ function castFloat($x, string $s, bool $b) {
     }
 
     if ((float) $s) {
-        assertType('non-falsy-string', $s);
+        assertType('string', $s);
     } else {
-        assertType("''|'0'", $s);
+        assertType("string", $s);
     }
 }

tests/PHPStan/Rules/Comparison/ElseIfConstantConditionRuleTest.php

@@ -4,6 +4,7 @@
 
 use PHPStan\Rules\Rule;
 use PHPStan\Testing\RuleTestCase;
+use const PHP_VERSION_ID;
 
 /**
  * @extends RuleTestCase<ElseIfConstantConditionRule>
@@ -121,4 +122,19 @@ public function testReportPhpDoc(): void
 		]);
 	}
 
+	public function testBug11674(): void
+	{
+		if (PHP_VERSION_ID < 80000) {
+			$this->markTestSkipped('Test requires PHP 8.0');
+		}
+
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-11674.php'], [
+			[
+				'Elseif condition is always false.',
+				28,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-11674.php

@@ -0,0 +1,40 @@
+<?php declare(strict_types = 1); // lint >= 8.0
+
+namespace Bug11674;
+
+class Test {
+
+	private ?string $param;
+
+	function show() : void {
+		if ((int) $this->param) {
+			echo 1;
+		} elseif ($this->param) {
+			echo 2;
+		}
+	}
+
+	function show2() : void {
+		if ((float) $this->param) {
+			echo 1;
+		} elseif ($this->param) {
+			echo 2;
+		}
+	}
+
+	function show3() : void {
+		if ((bool) $this->param) {
+			echo 1;
+		} elseif ($this->param) {
+			echo 2;
+		}
+	}
+
+	function show4() : void {
+		if ((string) $this->param) {
+			echo 1;
+		} elseif ($this->param) {
+			echo 2;
+		}
+	}
+}