Fix array intersection between HasOffsetType and HasOffsetValueType

phpstan-baseline.neon

@@ -1579,7 +1579,7 @@ parameters:
 
 		-
 			message: "#^Doing instanceof PHPStan\\\\Type\\\\Constant\\\\ConstantStringType is error\\-prone and deprecated\\. Use Type\\:\\:getConstantStrings\\(\\) instead\\.$#"
-			count: 4
+			count: 5
 			path: src/Type/TypeCombinator.php
 
 		-
@@ -1622,6 +1622,16 @@ parameters:
 			count: 1
 			path: src/Type/TypeCombinator.php
 
+		-
+			message: "#^Instanceof between PHPStan\\\\Type\\\\Constant\\\\ConstantIntegerType and PHPStan\\\\Type\\\\Constant\\\\ConstantIntegerType will always evaluate to true\\.$#"
+			count: 1
+			path: src/Type/TypeCombinator.php
+
+		-
+			message: "#^Result of \\|\\| is always true\\.$#"
+			count: 1
+			path: src/Type/TypeCombinator.php
+
 		-
 			message: "#^Doing instanceof PHPStan\\\\Type\\\\ArrayType is error\\-prone and deprecated\\. Use Type\\:\\:isArray\\(\\) or Type\\:\\:getArrays\\(\\) instead\\.$#"
 			count: 3

src/Type/TypeCombinator.php

@@ -591,6 +591,12 @@ private static function processArrayAccessoryTypes(array $arrayTypes): array
 					if (!($innerType instanceof AccessoryType) && !($innerType instanceof CallableType)) {
 						continue;
 					}
+					if ($innerType instanceof HasOffsetType) {
+						$offset = $innerType->getOffsetType();
+						if ($offset instanceof ConstantStringType || $offset instanceof ConstantIntegerType) {
+							$innerType = new HasOffsetValueType($offset, $arrayType->getIterableValueType());
+						}
+					}
 					if ($innerType instanceof HasOffsetValueType) {
 						$accessoryTypes[sprintf('hasOffsetValue(%s)', $innerType->getOffsetType()->describe(VerbosityLevel::cache()))][$i] = $innerType;
 						continue;

tests/PHPStan/Analyser/nsrt/bug-11518-types.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Bug11518Types;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param mixed[] $a
+ * @return array{thing: mixed}
+ * */
+function blah(array $a): array
+{
+	if (!array_key_exists('thing', $a)) {
+		$a['thing'] = 'bla';
+		assertType('hasOffsetValue(\'thing\', \'bla\')&non-empty-array', $a);
+	} else {
+		assertType('array&hasOffset(\'thing\')', $a);
+	}
+
+	assertType('array&hasOffsetValue(\'thing\', mixed)', $a);
+
+	return $a;
+}

tests/PHPStan/Rules/Functions/ReturnTypeRuleTest.php

@@ -283,4 +283,11 @@ public function testBug10732(): void
 		$this->analyse([__DIR__ . '/data/bug-10732.php'], []);
 	}
 
+	public function testBug11518(): void
+	{
+		$this->checkExplicitMixed = true;
+		$this->checkNullables = true;
+		$this->analyse([__DIR__ . '/data/bug-11518.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/bug-11518.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Bug11518;
+
+/**
+ * @param mixed[] $a
+ * @return array{thing: mixed}
+ * */
+function blah(array $a): array
+{
+	if (!array_key_exists('thing', $a)) {
+		$a['thing'] = 'bla';
+	}
+
+	return $a;
+}

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -978,7 +978,7 @@ public function dataUnion(): iterable
 					]),
 				],
 				IntersectionType::class,
-				'array&hasOffset(\'foo\')',
+				'array&hasOffsetValue(\'foo\', mixed)',
 			],
 			[
 				[
@@ -2568,6 +2568,21 @@ public function dataUnion(): iterable
 			ClosureType::class,
 			'Closure(): mixed',
 		];
+		yield [
+			[
+				new IntersectionType([
+					new ArrayType(new MixedType(), new MixedType()),
+					new NonEmptyArrayType(),
+					new HasOffsetValueType(new ConstantStringType('thing'), new ConstantStringType('bla')),
+				]),
+				new IntersectionType([
+					new ArrayType(new MixedType(), new MixedType()),
+					new HasOffsetType(new ConstantStringType('thing')),
+				]),
+			],
+			IntersectionType::class,
+			'array&hasOffsetValue(\'thing\', mixed)',
+		];
 	}
 
 	/**