[cfe] Avoid overcaching in const conditional simplication

The ConstConditionalSimplifier would try to cache the result of `VariableDeclaration`s but in doing so inadvertently cached parameter values in called extension type constructors.

This clears the cache between static invocation, thus avoid the overcaching between functions.

Closes #61222

Change-Id: I42f7eb4e0c689d119b88cfd1347baaedf1ff90dd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/444000
Reviewed-by: Mayank Patke <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>
Reviewed-by: Lasse Nielsen <[email protected]>
Reviewed-by: Stephen Adams <[email protected]>

Author: johnniwinther

pkg/front_end/lib/src/kernel/const_conditional_simplifier.dart

@@ -75,11 +75,12 @@ class ConstConditionalSimplifier extends RemovingTransformer {
     super.visitIfStatement(node, removalSentinel);
     Constant? condition = _evaluate(node.condition);
     if (condition is! BoolConstant) return node;
-    // Coverage-ignore(suite): Not run.
     if (condition.value) {
       return node.then;
     } else {
-      return node.otherwise ?? removalSentinel ?? new EmptyStatement();
+      return node.otherwise ??
+          removalSentinel ?? // Coverage-ignore(suite): Not run.
+          new EmptyStatement();
     }
   }
 
@@ -121,7 +122,8 @@ class ConstConditionalSimplifier extends RemovingTransformer {
 class _ConstantEvaluator extends TryConstantEvaluator {
   // TODO(fishythefish): Do caches need to be invalidated when the static type
   // context changes?
-  final Map<VariableDeclaration, Constant?> _variableCache = {};
+  /// Cache for local variables in the current method.
+  Map<VariableDeclaration, Constant?> _variableCache = {};
   final Map<Field, Constant?> _staticFieldCache = {};
   final Map<FunctionNode, Constant?> _functionCache = {};
   final Map<FunctionNode, Constant?> _localFunctionCache = {};
@@ -143,17 +145,14 @@ class _ConstantEvaluator extends TryConstantEvaluator {
 
   Constant? _evaluateFunctionInvocation(FunctionNode node) {
     if (node.typeParameters.isNotEmpty ||
-        // Coverage-ignore(suite): Not run.
         node.requiredParameterCount != 0 ||
-        // Coverage-ignore(suite): Not run.
         node.positionalParameters.isNotEmpty ||
-        // Coverage-ignore(suite): Not run.
         node.namedParameters.isNotEmpty) {
       return null;
     }
-    // Coverage-ignore-block(suite): Not run.
     Statement? body = node.body;
     if (body is! ReturnStatement) return null;
+    // Coverage-ignore-block(suite): Not run.
     Expression? expression = body.expression;
     if (expression == null) return null;
     return _evaluate(expression);
@@ -236,7 +235,16 @@ class _ConstantEvaluator extends TryConstantEvaluator {
 
   @override
   Constant visitStaticInvocation(StaticInvocation node) {
-    return _lookupStaticInvocation(node.target) ??
+    // Clear variable cache static invocations to avoid looking up cached
+    // variables from another call stack.
+    //
+    // This can occur when calling const extension type constructors since these
+    // are lowered into top level functions.
+    Map<VariableDeclaration, Constant?> oldCache = _variableCache;
+    _variableCache = {};
+    Constant result = _lookupStaticInvocation(node.target) ??
         super.visitStaticInvocation(node);
+    _variableCache = oldCache;
+    return result;
   }
 }

pkg/front_end/testcases/dart2wasm/issue61222.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2025, 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.
+
+void main() {
+  const [E.vn(), E.v1()];
+  var eList = <E>[?E.vn(), ?E.v1()];
+
+  const [C.vn(), C.v1()];
+  var cList = <C>[if (C.vn() != C.v1()) C.v1()];
+}
+
+extension type const E._(int? _) {
+  const E.vn() : this._(null);
+  const E.v1() : this._(1);
+}
+
+class C {
+  final int? field;
+  const C._(this.field);
+  const C.vn() : this._(null);
+  const C.v1() : this._(1);
+}

pkg/front_end/testcases/dart2wasm/issue61222.dart.strong.expect

@@ -0,0 +1,86 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object /*hasConstConstructor*/  {
+  final field core::int? field;
+  const constructor _(core::int? field) → self::C
+    : self::C::field = field, super core::Object::•()
+    ;
+  const constructor vn() → self::C
+    : this self::C::_(null)
+    ;
+  const constructor v1() → self::C
+    : this self::C::_(1)
+    ;
+  static synthetic method _#_#tearOff(core::int? field) → self::C
+    return new self::C::_(field);
+  static synthetic method _#vn#tearOff() → self::C
+    return new self::C::vn();
+  static synthetic method _#v1#tearOff() → self::C
+    return new self::C::v1();
+}
+extension type E(core::int? _) {
+  abstract extension-type-member representation-field get _() → core::int?;
+  constructor _ = self::E|constructor#_;
+  constructor tearoff _ = self::E|constructor#_#_#tearOff;
+  constructor vn = self::E|constructor#vn;
+  constructor tearoff vn = self::E|constructor#_#vn#tearOff;
+  constructor v1 = self::E|constructor#v1;
+  constructor tearoff v1 = self::E|constructor#_#v1#tearOff;
+}
+static method main() → void {
+  #C3;
+  core::List<self::E% /* erasure=core::int?, declared=! */> eList = block {
+    final core::List<self::E% /* erasure=core::int?, declared=! */> #t1 = <self::E% /* erasure=core::int?, declared=! */>[];
+    final self::E? /* erasure=core::int? */ #t2 = self::E|constructor#vn();
+    if(!(#t2 == null))
+      #t1.{core::List::add}{Invariant}(#t2{self::E% /* erasure=core::int?, declared=! */}){(self::E% /* erasure=core::int?, declared=! */) → void};
+    final self::E? /* erasure=core::int? */ #t3 = self::E|constructor#v1();
+    if(!(#t3 == null))
+      #t1.{core::List::add}{Invariant}(#t3{self::E% /* erasure=core::int?, declared=! */}){(self::E% /* erasure=core::int?, declared=! */) → void};
+  } =>#t1;
+  #C6;
+  core::List<self::C> cList = block {
+    final core::List<self::C> #t4 = <self::C>[];
+    if(!(new self::C::vn() =={core::Object::==}{(core::Object) → core::bool} new self::C::v1()))
+      #t4.{core::List::add}{Invariant}(new self::C::v1()){(self::C) → void};
+  } =>#t4;
+}
+static extension-type-member method E|constructor#_(core::int? _) → self::E% /* erasure=core::int?, declared=! */ {
+  lowered final self::E% /* erasure=core::int?, declared=! */ #this = _;
+  return #this;
+}
+static extension-type-member synthetic method E|constructor#_#_#tearOff(core::int? _) → self::E% /* erasure=core::int?, declared=! */
+  return self::E|constructor#_(_);
+static extension-type-member method E|constructor#vn() → self::E% /* erasure=core::int?, declared=! */ {
+  lowered final self::E% /* erasure=core::int?, declared=! */ #this;
+  #this = self::E|constructor#_(null);
+  return #this;
+}
+static extension-type-member synthetic method E|constructor#_#vn#tearOff() → self::E% /* erasure=core::int?, declared=! */
+  return self::E|constructor#vn();
+static extension-type-member method E|constructor#v1() → self::E% /* erasure=core::int?, declared=! */ {
+  lowered final self::E% /* erasure=core::int?, declared=! */ #this;
+  #this = self::E|constructor#_(1);
+  return #this;
+}
+static extension-type-member synthetic method E|constructor#_#v1#tearOff() → self::E% /* erasure=core::int?, declared=! */
+  return self::E|constructor#v1();
+
+constants  {
+  #C1 = null
+  #C2 = 1
+  #C3 = <core::int?>[#C1, #C2]
+  #C4 = self::C {field:#C1}
+  #C5 = self::C {field:#C2}
+  #C6 = <self::C>[#C4, #C5]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///issue61222.dart:
+- C.vn (from org-dartlang-testcase:///issue61222.dart:21:9)
+- C._ (from org-dartlang-testcase:///issue61222.dart:20:9)
+- Object. (from org-dartlang-sdk:///lib/core/object.dart)
+- C.v1 (from org-dartlang-testcase:///issue61222.dart:22:9)

pkg/front_end/testcases/dart2wasm/issue61222.dart.strong.transformed.expect

@@ -0,0 +1,92 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object /*hasConstConstructor*/  {
+  final field core::int? field;
+  const constructor _(final core::int? field) → self::C
+    : self::C::field = field, super core::Object::•()
+    ;
+  const constructor vn() → self::C
+    : this self::C::_(null)
+    ;
+  const constructor v1() → self::C
+    : this self::C::_(1)
+    ;
+  static synthetic method _#_#tearOff(final core::int? field) → self::C
+    return new self::C::_(field);
+  static synthetic method _#vn#tearOff() → self::C
+    return new self::C::vn();
+  static synthetic method _#v1#tearOff() → self::C
+    return new self::C::v1();
+}
+extension type E(core::int? _) {
+  abstract extension-type-member representation-field get _() → core::int?;
+  constructor _ = self::E|constructor#_;
+  constructor tearoff _ = self::E|constructor#_#_#tearOff;
+  constructor vn = self::E|constructor#vn;
+  constructor tearoff vn = self::E|constructor#_#vn#tearOff;
+  constructor v1 = self::E|constructor#v1;
+  constructor tearoff v1 = self::E|constructor#_#v1#tearOff;
+}
+static method main() → void {
+  #C3;
+  final core::List<self::E% /* erasure=core::int?, declared=! */> eList = block {
+    final core::List<self::E% /* erasure=core::int?, declared=! */> #t1 = <self::E% /* erasure=core::int?, declared=! */>[];
+    final self::E? /* erasure=core::int? */ #t2 = self::E|constructor#vn();
+    final self::E? /* erasure=core::int? */ #t3 = self::E|constructor#v1();
+    #t1.{core::List::add}{Invariant}(#t3{self::E% /* erasure=core::int?, declared=! */}){(self::E% /* erasure=core::int?, declared=! */) → void};
+  } =>#t1;
+  #C6;
+  final core::List<self::C> cList = block {
+    final core::List<self::C> #t4 = <self::C>[];
+    if(!(new self::C::vn() =={core::Object::==}{(core::Object) → core::bool} new self::C::v1()))
+      #t4.{core::List::add}{Invariant}(new self::C::v1()){(self::C) → void};
+  } =>#t4;
+}
+static extension-type-member method E|constructor#_(final core::int? _) → self::E% /* erasure=core::int?, declared=! */ {
+  lowered final self::E% /* erasure=core::int?, declared=! */ #this = _;
+  return #this;
+}
+static extension-type-member synthetic method E|constructor#_#_#tearOff(final core::int? _) → self::E% /* erasure=core::int?, declared=! */
+  return self::E|constructor#_(_);
+static extension-type-member method E|constructor#vn() → self::E% /* erasure=core::int?, declared=! */ {
+  lowered final self::E% /* erasure=core::int?, declared=! */ #this;
+  #this = self::E|constructor#_(null);
+  return #this;
+}
+static extension-type-member synthetic method E|constructor#_#vn#tearOff() → self::E% /* erasure=core::int?, declared=! */
+  return self::E|constructor#vn();
+static extension-type-member method E|constructor#v1() → self::E% /* erasure=core::int?, declared=! */ {
+  lowered final self::E% /* erasure=core::int?, declared=! */ #this;
+  #this = self::E|constructor#_(1);
+  return #this;
+}
+static extension-type-member synthetic method E|constructor#_#v1#tearOff() → self::E% /* erasure=core::int?, declared=! */
+  return self::E|constructor#v1();
+
+constants  {
+  #C1 = null
+  #C2 = 1
+  #C3 = <core::int?>[#C1, #C2]
+  #C4 = self::C {field:#C1}
+  #C5 = self::C {field:#C2}
+  #C6 = <self::C>[#C4, #C5]
+}
+
+Extra constant evaluation status:
+Evaluated: FactoryConstructorInvocation @ org-dartlang-testcase:///issue61222.dart:7:22 -> NullConstant(null)
+Evaluated: FactoryConstructorInvocation @ org-dartlang-testcase:///issue61222.dart:7:31 -> IntConstant(1)
+Evaluated: StaticInvocation @ org-dartlang-testcase:///issue61222.dart:14:23 -> NullConstant(null)
+Evaluated: StaticInvocation @ org-dartlang-testcase:///issue61222.dart:14:9 -> NullConstant(null)
+Evaluated: StaticInvocation @ org-dartlang-testcase:///issue61222.dart:15:23 -> IntConstant(1)
+Evaluated: StaticInvocation @ org-dartlang-testcase:///issue61222.dart:15:9 -> IntConstant(1)
+Extra constant evaluation: evaluated: 35, effectively constant: 6
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///issue61222.dart:
+- C.vn (from org-dartlang-testcase:///issue61222.dart:21:9)
+- C._ (from org-dartlang-testcase:///issue61222.dart:20:9)
+- Object. (from org-dartlang-sdk:///lib/core/object.dart)
+- C.v1 (from org-dartlang-testcase:///issue61222.dart:22:9)

pkg/front_end/testcases/dart2wasm/issue61222.dart.textual_outline.expect

@@ -0,0 +1,13 @@
+void main() {}
+
+extension type const E._(int? _) {
+  const E.vn() : this._(null);
+  const E.v1() : this._(1);
+}
+
+class C {
+  final int? field;
+  const C._(this.field);
+  const C.vn() : this._(null);
+  const C.v1() : this._(1);
+}

pkg/front_end/testcases/dart2wasm/issue61222.dart.textual_outline_modelled.expect

@@ -0,0 +1,13 @@
+class C {
+  const C._(this.field);
+  const C.v1() : this._(1);
+  const C.vn() : this._(null);
+  final int? field;
+}
+
+extension type const E._(int? _) {
+  const E.v1() : this._(1);
+  const E.vn() : this._(null);
+}
+
+void main() {}

tests/language/extension_type/regress_61222_test.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2025, 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.
+
+// This tests that extension constructor calls are not wrongfully optimized
+// away during const conditional simplication.
+
+import 'package:expect/expect.dart';
+
+void main() {
+  var eList = <E>[?E.vn(), ?E.v1()];
+  Expect.isTrue(eList.isNotEmpty);
+}
+
+extension type const E._(int? _) {
+  const E.vn() : this._(null);
+  const E.v1() : this._(1);
+}