[vm/aot/tfa] Handle references to tree-shaken closures

Sometimes inferred closure value may reference a closure
which was eliminated by the tree shaker (as tree-shaker can prune
deeper AST). That should not cause a crash and inferred closure value
should be disregarded.

TEST=pkg/vm/testcases/transformations/type_flow/transformer/eliminated_closure.dart
Fixes b/305730721

Change-Id: Ia26e620ebc06f949be1e05c734be65ce1d708b64
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/330661
Commit-Queue: Alexander Markov <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>

Author: alexmarkov

pkg/vm/lib/metadata/closure_id.dart

@@ -28,11 +28,12 @@ class ClosureIdMetadataRepository extends MetadataRepository<int> {
     return source.readUInt30();
   }
 
-  /// Return closure ID within the enclosing [Member].
+  /// Return closure ID within the enclosing [Member], or -1
+  /// if closure was not indexed.
   ///
   /// Closures should be indexed within enclosing [Member]
   /// using [indexClosures].
-  int getClosureId(LocalFunction closure) => mapping[closure]!;
+  int getClosureId(LocalFunction closure) => mapping[closure] ?? -1;
 
   /// Assign IDs for all closures within [member].
   void indexClosures(Member member) {

pkg/vm/lib/transformations/type_flow/transformer.dart

@@ -378,7 +378,14 @@ class AnnotateKernel extends RecursiveVisitor {
           if (function != null) {
             _closureIdMetadata.indexClosures(closureMember);
             closureId = _closureIdMetadata.getClosureId(function);
-            assert(closureId > 0);
+            if (closureId < 0) {
+              // Closure was tree-shaken and doesn't belong to
+              // the body of [closureMember].
+              closureMember = null;
+              closureId = 0;
+            } else {
+              assert(closureId > 0);
+            }
           } else {
             closureId = 0;
           }

pkg/vm/testcases/transformations/type_flow/transformer/eliminated_closure.dart

@@ -0,0 +1,34 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+abstract class A {
+  List<D> get bar;
+}
+
+class B implements A {
+  List<D> bar;
+  B(this.bar);
+}
+
+abstract class C {
+  A get foo;
+
+  String toString() => foo.bar.map((key) => key.baz((arg) {})).join('\n');
+}
+
+class D {
+  String baz(void Function(dynamic) callback) {
+    print(callback);
+    return 'hey';
+  }
+}
+
+class E extends C {
+  A get foo => throw 'Not today';
+}
+
+void main() {
+  print(D());
+  print(E());
+}

pkg/vm/testcases/transformations/type_flow/transformer/eliminated_closure.dart.expect

@@ -0,0 +1,36 @@
+library #lib;
+import self as self;
+import "dart:core" as core;
+
+abstract class A extends core::Object {
+}
+abstract class C extends core::Object {
+  synthetic constructor •() → self::C
+    : super core::Object::•()
+    ;
+[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,getterSelectorId:1]  abstract get foo() → self::A;
+[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:2,getterSelectorId:3] [@vm.closure-id=0]  method toString() → core::String
+    return block {
+      [@vm.direct-call.metadata=#lib::E.foo] [@vm.inferred-type.metadata=!] this.{self::C::foo}{self::A};
+    } =>throw "Attempt to execute code removed by Dart AOT compiler (TFA)";
+}
+class D extends core::Object {
+  synthetic constructor •() → self::D
+    : super core::Object::•()
+    ;
+[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:4,getterSelectorId:5]  method baz([@vm.inferred-arg-type.metadata=dart.core::_Closure] (dynamic) → void callback) → core::String {
+    core::print(callback);
+    return "hey";
+  }
+}
+class E extends self::C {
+  synthetic constructor •() → self::E
+    : super self::C::•()
+    ;
+[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,getterSelectorId:1]  get foo() → self::A
+    return throw "Not today";
+}
+static method main() → void {
+  core::print(new self::D::•());
+  core::print(new self::E::•());
+}