Handle instanceof self/static/parent narrowing

Author: AJenbo

docs/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **`instanceof self/static/parent` narrowing.** Type narrowing with `instanceof self`, `instanceof static`, and `instanceof parent` now works correctly in all contexts (assert, if-blocks, guard clauses, compound conditions). Previously these keywords were ignored because the AST parser produces dedicated node types rather than identifiers, and `parent` was not recognized as a type hint during resolution.
 - **Variable type after reassignment.** When a method parameter is reassigned mid-body (e.g. `$file = $result->getFile()`), subsequent member accesses now resolve against the new type instead of the original parameter type. Previously the diagnostic subject cache reused the first resolution for the entire method scope, producing false-positive "not found" warnings on members that exist only on the reassigned type.
 - **Null-safe method chain resolution.** Null-safe method calls (`$obj?->method()`) now resolve the return type correctly for variable type inference, including cross-file chains. Previously `?->` calls were ignored by the RHS resolution pipeline, losing the type for any variable assigned from a null-safe chain.
 - **Nullable and generic types in class lookup.** Variables typed as `?ClassName` or `Collection<Item>` now resolve correctly across all code paths. Previously the `?` prefix and generic parameters were not stripped before class lookup, causing the type engine to treat them as unknown types. This fixes completion, hover, go-to-definition, and false-positive diagnostics for any variable whose type uses the nullable shorthand or carries generic arguments.

docs/todo/bugs.md

@@ -15,36 +15,6 @@ within the same impact tier.
 
 ---
 
-#### B9. `assert($x instanceof self)` narrowing ignores `self`/`static`/`parent`
-
-| | |
-|---|---|
-| **Impact** | Medium-High |
-| **Effort** | Low |
-
-`try_extract_instanceof` in `completion/types/narrowing.rs` only matches
-`Expression::Identifier` for the RHS of an `instanceof` check. When the
-RHS is `self`, `static`, or `parent`, the Mago AST produces
-`Expression::Self_`, `Expression::Static`, or `Expression::Parent`
-instead, which fall through to `None`. This means
-`assert($feature instanceof self)` never narrows the variable.
-
-The fix is to add three arms to the `match bin.rhs` block in
-`try_extract_instanceof` that map `Self_` → `"self"`, `Static` →
-`"static"`, `Parent` → `"parent"`. The downstream
-`apply_instanceof_inclusion` already resolves `"self"` etc. to the
-current class via `type_hint_to_classes`.
-
-**Reproduce:** any method with a `BaseCatalogFeature` parameter that
-calls `assert($feature instanceof self)` then accesses subclass-only
-methods on `$feature`. Also affects Mockery test patterns:
-`$mock = $this->mock(X::class); assert($mock instanceof X);`.
-
-**Triage count:** ~30 diagnostics in luxplus/shared (18 BaseCatalogFeature,
-11 MockInterface, 1 Elasticsearch).
-
----
-
 #### B10. Negative narrowing after early return not applied
 
 | | |

example.php

@@ -211,6 +211,34 @@ public function demo(): void
 }
 
 
+// ── instanceof self/static/parent Narrowing ────────────────────────────────
+
+class InstanceofSelfDemo extends ScaffoldingSedan
+{
+    public function sport(): void {}
+
+    public function demo(ScaffoldingMotor $m): void
+    {
+        // instanceof self — narrows to InstanceofSelfDemo
+        assert($m instanceof self);
+        $m->cruise();                             // inherited from ScaffoldingSedan
+        $m->sport();                              // own method via self narrowing
+
+        // instanceof static — narrows to InstanceofSelfDemo
+        $x = getUnknownValue();
+        if ($x instanceof static) {
+            $x->sport();                          // narrowed to static (this class)
+        }
+
+        // instanceof parent — narrows to ScaffoldingSedan
+        $y = getUnknownValue();
+        if ($y instanceof parent) {
+            $y->cruise();                         // narrowed to parent (ScaffoldingSedan)
+        }
+    }
+}
+
+
 // ── Custom Assert Narrowing ─────────────────────────────────────────────────
 
 class AssertNarrowingDemo
@@ -2659,6 +2687,16 @@ public function map(string $signature, mixed $source): Pen|Marker
 
 // ── Demo-Specific Scaffolding ───────────────────────────────────────────────
 
+class ScaffoldingMotor
+{
+    public function start(): void {}
+}
+
+class ScaffoldingSedan extends ScaffoldingMotor
+{
+    public function cruise(): void {}
+}
+
 abstract class ScaffoldingAbstractShape
 {
     abstract public function area(): float;
@@ -4351,6 +4389,17 @@ function runDemoAssertions(): void
     assert(StaticAssert::isRock(new Rock()) === true, 'StaticAssert::isRock(Rock) must return true');
     assert(StaticAssert::isNotRock(new Banana()) === true, 'StaticAssert::isNotRock(Banana) must return true');
 
+    // ── instanceof self/static/parent ───────────────────────────────────
+    $sedan = new ScaffoldingSedan();
+    assert($sedan instanceof ScaffoldingMotor, 'ScaffoldingSedan must extend ScaffoldingMotor');
+    assert(method_exists($sedan, 'cruise'), 'ScaffoldingSedan must have cruise()');
+    assert(method_exists($sedan, 'start'), 'ScaffoldingSedan must inherit start()');
+
+    $demo = new InstanceofSelfDemo();
+    assert($demo instanceof ScaffoldingSedan, 'InstanceofSelfDemo must extend ScaffoldingSedan');
+    assert(method_exists($demo, 'sport'), 'InstanceofSelfDemo must have sport()');
+    assert(method_exists($demo, 'cruise'), 'InstanceofSelfDemo must inherit cruise()');
+
     // ── Method-level @template (runtime resolution) ─────────────────────
     $locator = new ServiceLocator();
     $locatedPen = $locator->get(Pen::class);

src/completion/types/narrowing.rs

@@ -378,6 +378,9 @@ pub(in crate::completion) fn try_extract_instanceof<'b>(
             // RHS is the class name
             match bin.rhs {
                 Expression::Identifier(ident) => Some(ident.value().to_string()),
+                Expression::Self_(_) => Some("self".to_string()),
+                Expression::Static(_) => Some("static".to_string()),
+                Expression::Parent(_) => Some("parent".to_string()),
                 _ => None,
             }
         }

src/completion/types/resolution.rs

@@ -211,6 +211,25 @@ fn type_hint_to_classes_depth(
             .collect();
     }
 
+    // `parent` refers to the parent class of the owning class.
+    if hint == "parent" {
+        let parent_name = all_classes
+            .iter()
+            .find(|c| c.name == owning_class_name)
+            .and_then(|c| c.parent_class.clone())
+            .or_else(|| class_loader(owning_class_name).and_then(|c| c.parent_class.clone()));
+        if let Some(parent) = parent_name {
+            return all_classes
+                .iter()
+                .find(|c| c.name == parent)
+                .map(|c| ClassInfo::clone(c))
+                .or_else(|| class_loader(&parent).map(Arc::unwrap_or_clone))
+                .into_iter()
+                .collect();
+        }
+        return vec![];
+    }
+
     // ── Parse generic arguments (if any) ──
     // `Collection<int, User>` → base_hint = `Collection`, generic_args = ["int", "User"]
     // `Foo`                   → base_hint = `Foo`,        generic_args = []