Improve unsetting constant offsets on array

src/Type/ArrayType.php

@@ -297,6 +297,20 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $uni
 
 	public function unsetOffset(Type $offsetType): Type
 	{
+		$offsetType = self::castToArrayKeyType($offsetType);
+
+		if (
+			($offsetType instanceof ConstantIntegerType || $offsetType instanceof ConstantStringType)
+			&& !$this->keyType->isSuperTypeOf($offsetType)->no()
+		) {
+			$keyType = TypeCombinator::remove($this->keyType, $offsetType);
+			if ($keyType instanceof NeverType) {
+				return new ConstantArrayType([], []);
+			}
+
+			return new self($keyType, $this->itemType);
+		}
+
 		return $this;
 	}
 

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -1043,6 +1043,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8017.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8004.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/global-namespace.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/array-offset-unset.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/array-offset-unset.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace ArrayOffsetUnset;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param array<0|1, mixed> $list
+ */
+function foo(array $list) {
+	assertType('array<0|1, mixed>', $list);
+	unset($list[0]);
+	assertType('array<1, mixed>', $list);
+	unset($list[1]);
+	assertType('array{}', $list);
+}

tests/PHPStan/Analyser/data/bug-2648.php

@@ -15,7 +15,7 @@ public function doFoo(array $list): void
 		if (count($list) > 1) {
 			assertType('int<2, max>', count($list));
 			unset($list['fooo']);
-			assertType('array<bool>', $list);
+			assertType("array<mixed~'fooo', bool>", $list);
 			assertType('int<0, max>', count($list));
 		}
 	}

tests/PHPStan/Analyser/data/bug-4016.php

@@ -17,7 +17,7 @@ public function doFoo(array $a): void
 		assertType('non-empty-array<int, int>', $a);
 
 		unset($a[0]);
-		assertType('array<int, int>', $a);
+		assertType('array<int<min, -1>|int<1, max>, int>', $a);
 	}
 
 	/**
@@ -30,7 +30,7 @@ public function doBar(array $a): void
 		assertType('non-empty-array<int, int>&hasOffsetValue(1, 2)', $a);
 
 		unset($a[1]);
-		assertType('array<int, int>', $a);
+		assertType('array<int<min, 0>|int<2, max>, int>', $a);
 	}
 
 }

tests/PHPStan/Analyser/data/bug-6399.php

@@ -54,7 +54,7 @@ public function doBar(array $a): void
 	{
 		assertType('non-empty-array', $a);
 		unset($a[1]);
-		assertType('array', $a);
+		assertType('array<mixed~1, mixed>', $a);
 	}
 
 }

tests/PHPStan/Analyser/data/composer-array-bug.php

@@ -49,7 +49,7 @@ public function doFoo(): void
 
 			if (empty($this->config['authors'])) {
 				unset($this->config['authors']);
-				assertType("array", $this->config);
+				assertType("array<mixed~'authors', mixed>", $this->config);
 			} else {
 				assertType("array&hasOffsetValue('authors', mixed~0|0.0|''|'0'|array{}|false|null)", $this->config);
 			}

tests/PHPStan/Analyser/data/list-type.php

@@ -86,7 +86,7 @@ public function withFullListFunctionality(): void
 		$list[] = '1';
 		$list[] = '2';
 		unset($list[0]);//break list behaviour
-		assertType('array<int, mixed>', $list);
+		assertType('array<int<min, -1>|int<1, max>, mixed>', $list);
 
 		/** @var list $list2 */
 		$list2 = [];

tests/PHPStan/Rules/Variables/data/bug-3391.php

@@ -26,7 +26,7 @@ public function test()
 
 		unset($data['id']);
 
-		assertType("array&hasOffsetValue('bar', 'b')&hasOffsetValue('foo', 'a')", $data);
+		assertType("array<mixed~'id', mixed>&hasOffsetValue('bar', 'b')&hasOffsetValue('foo', 'a')", $data);
 		return $data;
 	}
 }