TASK: Add ExpressionTypeNarrowerTest

src/TypeSystem/Narrower/NarrowedTypes.php

@@ -53,4 +53,10 @@ public function getType(string $identifierName): ?TypeInterface
     {
         return $this->types[$identifierName] ?? null;
     }
+
+    /** @return array<string,TypeInterface> */
+    public function toArray(): array
+    {
+        return $this->types;
+    }
 }

test/Unit/TypeSystem/Narrower/ExpressionTypeNarrowerTest.php

@@ -0,0 +1,104 @@
+<?php
+
+/**
+ * PackageFactory.ComponentEngine - Universal View Components for PHP
+ *   Copyright (C) 2022 Contributors of PackageFactory.ComponentEngine
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace PackageFactory\ComponentEngine\Test\Unit\TypeSystem\Narrower;
+
+
+use PackageFactory\ComponentEngine\Parser\Ast\ExpressionNode;
+use PackageFactory\ComponentEngine\Test\Unit\TypeSystem\Scope\Fixtures\DummyScope;
+use PackageFactory\ComponentEngine\TypeSystem\Narrower\ExpressionTypeNarrower;
+use PackageFactory\ComponentEngine\TypeSystem\Narrower\NarrowedTypes;
+use PackageFactory\ComponentEngine\TypeSystem\Narrower\TypeNarrowerContext;
+use PackageFactory\ComponentEngine\TypeSystem\Type\NullType\NullType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\StringType\StringType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\UnionType\UnionType;
+use PHPUnit\Framework\TestCase;
+
+final class ExpressionTypeNarrowerTest extends TestCase
+{
+    public function narrowedExpressionsExamples(): mixed
+    {
+        return [
+            'nullableString' => [
+                'nullableString',
+                $variableIsString = NarrowedTypes::fromEntry('nullableString', StringType::get())
+            ],
+
+            'nullableString === null' => [
+                'nullableString === null',
+                $variableIsNull = NarrowedTypes::fromEntry('nullableString', NullType::get())
+            ],
+            // Patience you must have my young Padawan.
+            'null === nullableString' => [
+                'null === nullableString', $variableIsNull
+            ],
+
+            'nullableString !== null' => [
+                'nullableString !== null', $variableIsString
+            ],
+            'null !== nullableString' => [
+                'null !== nullableString', $variableIsString
+            ],
+
+            'true === (nullableString === null)' => [
+                'true === (nullableString === null)', $variableIsNull
+            ],
+            'false !== (nullableString === null)' => [
+                'false !== (nullableString === null)', $variableIsNull
+            ],
+
+            'false === (nullableString === null)' => [
+                'false === (nullableString === null)', $variableIsString
+            ],
+            'true !== (nullableString === null)' => [
+                'true !== (nullableString === null)', $variableIsString
+            ],
+
+            'nullableString === variableOfTypeNull' => [
+                'nullableString === variableOfTypeNull', $variableIsNull
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider narrowedExpressionsExamples
+     * @test
+     */
+    public function narrowedExpressions(string $expressionAsString, NarrowedTypes $expectedTypes): void
+    {
+        $expressionTypeNarrower = new ExpressionTypeNarrower(
+            scope: new DummyScope([
+                'nullableString' => UnionType::of(StringType::get(), NullType::get()),
+                'variableOfTypeNull' => NullType::get()
+            ])
+        );
+
+        $expressionNode = ExpressionNode::fromString($expressionAsString);
+
+        $actualTypes = $expressionTypeNarrower->narrowTypesOfSymbolsIn($expressionNode, TypeNarrowerContext::TRUTHY);
+
+        $this->assertEqualsCanonicalizing(
+            $expectedTypes->toArray(),
+            $actualTypes->toArray()
+        );
+    }
+}

test/Unit/TypeSystem/Resolver/TernaryOperation/TernaryOperationTypeResolverTest.php

@@ -63,31 +63,6 @@ public function ternaryOperationExamples(): array
             'null === nullableString ? "" : nullableString' => [
                 'null === nullableString ? "" : nullableString', StringType::get()
             ],
-
-            'nullableString !== null ? nullableString : ""' => [
-                'nullableString !== null ? nullableString : ""', StringType::get()
-            ],
-            'null !== nullableString ? nullableString : ""' => [
-                'null !== nullableString ? nullableString : ""', StringType::get()
-            ],
-
-            'true === (nullableString === null) ? "" : nullableString' => [
-                'true === (nullableString === null) ? "" : nullableString', StringType::get()
-            ],
-            'false !== (nullableString === null) ? "" : nullableString' => [
-                'false !== (nullableString === null) ? "" : nullableString', StringType::get()
-            ],
-
-            'false === (nullableString === null) ? nullableString : ""' => [
-                'false === (nullableString === null) ? nullableString : ""', StringType::get()
-            ],
-            'true !== (nullableString === null) ? nullableString : ""' => [
-                'true !== (nullableString === null) ? nullableString : ""', StringType::get()
-            ],
-
-            'nullableString === variableOfTypeNull ? "" : nullableString' => [
-                'nullableString === variableOfTypeNull ? "" : nullableString', StringType::get()
-            ],
         ];
     }
 
@@ -103,7 +78,6 @@ public function resolvesTernaryOperationToResultingType(string $ternaryExpressio
         $scope = new DummyScope([
             'variableOfTypeString' => StringType::get(),
             'variableOfTypeNumber' => NumberType::get(),
-            'variableOfTypeNull' => NullType::get(),
             'nullableString' => UnionType::of(StringType::get(), NullType::get())
         ]);
         $ternaryOperationTypeResolver = new TernaryOperationTypeResolver(