TASK: Cleanup InferredTypes and extract duplicated logic to TypeInferrerContext

Author: mhsdesign

src/TypeSystem/Inferrer/InferredTypes.php

@@ -27,13 +27,30 @@
 class InferredTypes
 {
     /**
-     * @var TypeInterface[]
+     * Map of identifierName to the corresponding inferred type
+     * @var array<string,TypeInterface>
      */
-    public readonly array $types;
+    private readonly array $types;
 
-    public function __construct(
+    private function __construct(
         TypeInterface ...$types
     ) {
+        // @phpstan-ignore-next-line
         $this->types = $types;
     }
+
+    public static function empty(): self
+    {
+        return new self();
+    }
+
+    public static function fromType(string $identifierName, TypeInterface $type): self
+    {
+        return new self(...[$identifierName => $type]);
+    }
+
+    public function getType(string $identifierName): ?TypeInterface
+    {
+        return $this->types[$identifierName] ?? null;
+    }
 }

src/TypeSystem/Inferrer/TypeInferrer.php

@@ -53,22 +53,19 @@ public function inferTypesInCondition(ExpressionNode $conditionNode, TypeInferre
     {
         if ($conditionNode->root instanceof IdentifierNode) {
             $type = $this->scope->lookupTypeFor($conditionNode->root->value);
-            // case `nullableString ? "nullableString is not null" : "nullableString is null"`
-            if (!$type instanceof UnionType || !$type->containsNull()) {
-                return new InferredTypes();
+            if (!$type) {
+                return InferredTypes::empty();
             }
-
-            return new InferredTypes(
-                ...[$conditionNode->root->value => $context->isTrue() ? $type->withoutNull() : NullType::get()]
-            );
+            // case `nullableString ? "nullableString is not null" : "nullableString is null"`
+            return InferredTypes::fromType($conditionNode->root->value, $context->narrowDownType($type));
         }
 
         if (($binaryOperationNode = $conditionNode->root) instanceof BinaryOperationNode) {
             // cases
             // `nullableString === null ? "nullableString is null" : "nullableString is not null"`
             // `nullableString !== null ? "nullableString is not null" : "nullableString is null"`
             if (count($binaryOperationNode->operands->rest) !== 1) {
-                return new InferredTypes();
+                return InferredTypes::empty();
             }
             $first = $binaryOperationNode->operands->first;
             $second = $binaryOperationNode->operands->rest[0];
@@ -82,26 +79,21 @@ public function inferTypesInCondition(ExpressionNode $conditionNode, TypeInferre
             };
 
             if ($comparedIdentifierValueToNull === null) {
-                return new InferredTypes();
+                return InferredTypes::empty();
             }
-
             $type = $this->scope->lookupTypeFor($comparedIdentifierValueToNull);
-            if (!$type instanceof UnionType || !$type->containsNull()) {
-                return new InferredTypes();
+            if (!$type) {
+                return InferredTypes::empty();
             }
 
             if ($binaryOperationNode->operator === BinaryOperator::EQUAL) {
-                return new InferredTypes(
-                    ...[$comparedIdentifierValueToNull => $context->isTrue() ? NullType::get() : $type->withoutNull()]
-                );
+                return InferredTypes::fromType($comparedIdentifierValueToNull, $context->negate()->narrowDownType($type));
             }
             if ($binaryOperationNode->operator === BinaryOperator::NOT_EQUAL) {
-                return new InferredTypes(
-                    ...[$comparedIdentifierValueToNull => $context->isTrue() ? $type->withoutNull() : NullType::get()]
-                );
+                return InferredTypes::fromType($comparedIdentifierValueToNull, $context->narrowDownType($type));
             }
         }
 
-        return new InferredTypes();
+        return InferredTypes::empty();
     }
 }

src/TypeSystem/Inferrer/TypeInferrerContext.php

@@ -22,19 +22,32 @@
 
 namespace PackageFactory\ComponentEngine\TypeSystem\Inferrer;
 
+use PackageFactory\ComponentEngine\TypeSystem\Type\NullType\NullType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\UnionType\UnionType;
+use PackageFactory\ComponentEngine\TypeSystem\TypeInterface;
+
 enum TypeInferrerContext
 {
     case TRUTHY;
 
     case FALSY;
 
-    public function isTrue(): bool
+    public function negate(): self
     {
-        return $this === self::TRUTHY;
+        return match ($this) {
+            self::TRUTHY => self::FALSY,
+            self::FALSY => self::TRUTHY
+        };
     }
 
-    public function isFalse(): bool
+    public function narrowDownType(TypeInterface $type): TypeInterface
     {
-        return $this === self::FALSY;
+        if (!$type instanceof UnionType || !$type->containsNull()) {
+            return $type;
+        }
+        return match ($this) {
+            self::TRUTHY => $type->withoutNull(),
+            self::FALSY => NullType::get()
+        };
     }
 }

src/TypeSystem/Scope/TernaryBranchScope/TernaryBranchScope.php

@@ -56,7 +56,7 @@ public static function forFalsyBranch(ExpressionNode $conditionNode, ScopeInterf
 
     public function lookupTypeFor(string $name): ?TypeInterface
     {
-        return $this->inferredTypes->types[$name] ?? $this->parentScope->lookupTypeFor($name);
+        return $this->inferredTypes->getType($name) ?? $this->parentScope->lookupTypeFor($name);
     }
 
     public function resolveTypeReference(TypeReferenceNode $typeReferenceNode): TypeInterface