Consistently return ErrorType for invalid keys

Author: herndlm

src/Type/ArrayType.php

@@ -369,10 +369,14 @@ public function unsetOffset(Type $offsetType): Type
 
 	public function fillKeysArray(Type $valueType): Type
 	{
-		$itemType = $this->getIterableValueType();
+		$itemType = $this->getItemType();
+		if ((new IntegerType())->isSuperTypeOf($itemType)->no()) {
+			$stringKeyType = $itemType->toString();
+			if ($stringKeyType instanceof ErrorType) {
+				return $stringKeyType;
+			}
 
-		if ((new IntegerType())->isSuperTypeOf($itemType)->no() && !$itemType->toString() instanceof ErrorType) {
-			return new ArrayType($itemType->toString(), $valueType);
+			return new ArrayType($stringKeyType, $valueType);
 		}
 
 		return new ArrayType($itemType, $valueType);

src/Type/Constant/ConstantArrayType.php

@@ -677,11 +677,12 @@ public function fillKeysArray(Type $valueType): Type
 
 		foreach ($this->valueTypes as $i => $keyType) {
 			if ((new IntegerType())->isSuperTypeOf($keyType)->no()) {
-				if ($keyType->toString() instanceof ErrorType) {
-					return new NeverType();
+				$stringKeyType = $keyType->toString();
+				if ($stringKeyType instanceof ErrorType) {
+					return $stringKeyType;
 				}
 
-				$builder->setOffsetValueType($keyType->toString(), $valueType, $this->isOptionalKey($i));
+				$builder->setOffsetValueType($stringKeyType, $valueType, $this->isOptionalKey($i));
 			} else {
 				$builder->setOffsetValueType($keyType, $valueType, $this->isOptionalKey($i));
 			}

tests/PHPStan/Analyser/data/array-fill-keys.php

@@ -48,7 +48,7 @@ function withObjectKey() : array
 {
 	assertType("array{foo: 'b'}", array_fill_keys([new Foo()], 'b'));
 	assertType("non-empty-array<string, 'b'>", array_fill_keys([new Bar()], 'b'));
-	assertType("*NEVER*", array_fill_keys([new Baz()], 'b'));
+	assertType("*ERROR*", array_fill_keys([new Baz()], 'b'));
 }
 
 function withUnionKeys(): void
@@ -94,7 +94,7 @@ function withNotConstantArray(array $foo, array $bar, array $baz, array $floats,
 	assertType("array<numeric-string, null>", array_fill_keys($floats, null));
 	assertType("array<bool|int|string, null>", array_fill_keys($mixed, null));
 	assertType('array<string, null>', array_fill_keys($list, null));
-	assertType('array<ArrayFillKeys\Baz, null>', array_fill_keys($objectsWithoutToString, null)); // should be *NEVER* or *ERROR* according to https://3v4l.org/gGpic?
+	assertType('*ERROR*', array_fill_keys($objectsWithoutToString, null));
 
 	if (array_key_exists(17, $mixed)) {
 		assertType('non-empty-array<bool|int|string, null>', array_fill_keys($mixed, null));