Binary operations on non-empty-string and string should error

src/Analyser/MutatingScope.php

@@ -1400,6 +1400,11 @@ private function resolveType(Expr $node): Type
 				return new ErrorType();
 			}
 
+			if ($leftType->isNonEmptyString()->yes() && !$leftType->isNumericString()->yes() ||
+				$rightType->isNonEmptyString()->yes() && !$rightType->isNumericString()->yes()) {
+				return new ErrorType();
+			}
+
 			$leftNumberType = $leftType->toNumber();
 			$rightNumberType = $rightType->toNumber();
 
@@ -1419,6 +1424,12 @@ private function resolveType(Expr $node): Type
 
 			$resultType = TypeCombinator::union($leftNumberType, $rightNumberType);
 			if ($node instanceof Expr\AssignOp\Div || $node instanceof Expr\BinaryOp\Div) {
+				// division on strings is not allowed. its allowed on numeric strings though.
+				if ($leftType->isString()->yes() && !$leftType->isNumericString()->yes() && !$leftType->isLiteralString()->yes()
+					|| $rightType->isString()->yes() && !$rightType->isNumericString()->yes() && !$rightType->isLiteralString()->yes()) {
+					return new ErrorType();
+				}
+
 				if ($types instanceof MixedType || $resultType instanceof IntegerType) {
 					return new BenevolentUnionType([new IntegerType(), new FloatType()]);
 				}

src/Type/Accessory/AccessoryLiteralStringType.php

@@ -164,6 +164,11 @@ public function toArray(): Type
 		);
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createMaybe();

src/Type/Accessory/AccessoryNonEmptyStringType.php

@@ -160,6 +160,11 @@ public function toArray(): Type
 		);
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createMaybe();

src/Type/Accessory/AccessoryNumericStringType.php

@@ -156,6 +156,11 @@ public function toArray(): Type
 		);
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createYes();

src/Type/Accessory/HasOffsetType.php

@@ -134,6 +134,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createMaybe();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createMaybe();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createMaybe();

src/Type/Accessory/NonEmptyArrayType.php

@@ -139,6 +139,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createYes();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/ArrayType.php

@@ -199,6 +199,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createYes();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/CallableType.php

@@ -304,6 +304,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createMaybe();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createMaybe();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/ClassStringType.php

@@ -62,6 +62,11 @@ public function isSuperTypeOf(Type $type): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createMaybe();

src/Type/ClosureType.php

@@ -381,6 +381,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/Constant/ConstantStringType.php

@@ -240,6 +240,11 @@ public function toFloat(): Type
 		return new ConstantFloatType((float) $this->value);
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createFromBoolean(is_numeric($this->getValue()));

src/Type/FloatType.php

@@ -118,6 +118,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/IntersectionType.php

@@ -349,6 +349,11 @@ public function isArray(): TrinaryLogic
 		return $this->intersectResults(static fn (Type $type): TrinaryLogic => $type->isArray());
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return $this->intersectResults(static fn (Type $type): TrinaryLogic => $type->isString());
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return $this->intersectResults(static fn (Type $type): TrinaryLogic => $type->isNumericString());

src/Type/IterableType.php

@@ -228,6 +228,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createMaybe();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/JustNullableTypeTrait.php

@@ -58,6 +58,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/MixedType.php

@@ -405,6 +405,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createMaybe();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createMaybe();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createMaybe();

src/Type/NeverType.php

@@ -231,6 +231,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/NullType.php

@@ -175,6 +175,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/ObjectType.php

@@ -779,6 +779,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/StaticType.php

@@ -332,6 +332,11 @@ public function isArray(): TrinaryLogic
 		return $this->getStaticObjectType()->isArray();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return $this->getStaticObjectType()->isString();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return $this->getStaticObjectType()->isNumericString();

src/Type/StrictMixedType.php

@@ -151,6 +151,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/StringType.php

@@ -133,6 +133,11 @@ public function toArray(): Type
 		);
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createMaybe();

src/Type/Traits/ObjectTypeTrait.php

@@ -105,6 +105,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

src/Type/Type.php

@@ -98,6 +98,11 @@ public function isSmallerThan(Type $otherType): TrinaryLogic;
 
 	public function isSmallerThanOrEqual(Type $otherType): TrinaryLogic;
 
+	/**
+	 * Whether the type is a plain string, and not one of the further specialized string-types.
+	 */
+	public function isString(): TrinaryLogic;
+
 	public function isNumericString(): TrinaryLogic;
 
 	public function isNonEmptyString(): TrinaryLogic;

src/Type/UnionType.php

@@ -391,6 +391,11 @@ public function isArray(): TrinaryLogic
 		return $this->unionResults(static fn (Type $type): TrinaryLogic => $type->isArray());
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return $this->unionResults(static fn (Type $type): TrinaryLogic => $type->isString());
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return $this->unionResults(static fn (Type $type): TrinaryLogic => $type->isNumericString());

src/Type/VoidType.php

@@ -100,6 +100,11 @@ public function isArray(): TrinaryLogic
 		return TrinaryLogic::createNo();
 	}
 
+	public function isString(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 	public function isNumericString(): TrinaryLogic
 	{
 		return TrinaryLogic::createNo();

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -704,6 +704,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6500.php');
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6488.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6624.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-6624.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Bug6624;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param non-empty-string $foo
+ * @param string $bar
+ */
+function bug6624_should_error($foo, $bar) {
+	assertType('*ERROR*',$foo + 10);
+	assertType('*ERROR*',$foo - 10);
+	assertType('*ERROR*',$foo * 10);
+	assertType('*ERROR*',$foo / 10);
+
+	assertType('*ERROR*',10 + $foo);
+	assertType('*ERROR*',10 - $foo);
+	assertType('*ERROR*',10 * $foo);
+	assertType('*ERROR*',10 / $foo);
+
+	assertType('*ERROR*',$bar + 10);
+	assertType('*ERROR*',$bar - 10);
+	assertType('*ERROR*',$bar * 10);
+	assertType('*ERROR*',$bar / 10);
+
+	assertType('*ERROR*',10 + $bar);
+	assertType('*ERROR*',10 - $bar);
+	assertType('*ERROR*',10 * $bar);
+	assertType('*ERROR*',10 / $bar);
+}

tests/PHPStan/Rules/Api/data/class-implements-out-of-phpstan.php

@@ -234,6 +234,11 @@ public function isSmallerThanOrEqual(Type $otherType): \PHPStan\TrinaryLogic
 		// TODO: Implement isSmallerThanOrEqual() method.
 	}
 
+	public function isString(): \PHPStan\TrinaryLogic
+	{
+		// TODO: Implement isString() method.
+	}
+
 	public function isNumericString(): \PHPStan\TrinaryLogic
 	{
 		// TODO: Implement isNumericString() method.