[dart2js] Fix reduction to declared type in type promotion computation

When reducing the type promotion in case of assignment, the target
info wasn't correctly handling the reduction to the trivial state.
This caused an error in a following join computation.


Closes #42281

Change-Id: I2144f5401e9736308dc37147f7a5cb9ab1be8583
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150935
Commit-Queue: Stephen Adams <[email protected]>
Reviewed-by: Stephen Adams <[email protected]>

Author: johnniwinther

pkg/compiler/lib/src/ir/static_type.dart

@@ -1940,7 +1940,13 @@ class TypeMap {
             newTypesOfInterest.add(typeOfInterest);
           }
         }
-        if (newTypesOfInterest.isNotEmpty) {
+        if (newTypesOfInterest.length > 1 ||
+            (newTypesOfInterest.length == 1 &&
+                newTypesOfInterest.single != info.declaredType)) {
+          // If [newTypesOfInterest] only contains the we have no information
+          // about the variable (it is either an instance of its declared type
+          // or null) and the canonical way to represent this is to have _no_
+          // target info.
           TypeHolder typeHolderIfNonNull =
               new TypeHolder(info.declaredType, newTypesOfInterest, null);
           TypeHolder typeHolderIfNull = new TypeHolder(info.declaredType, null,

pkg/compiler/test/static_type/data/issue42281.dart

@@ -0,0 +1,64 @@
+// Copyright (c) 2020, 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.
+
+class Class {
+  final Type componentType;
+
+  Class(this.componentType);
+}
+
+class SubClass extends Class {
+  SubClass(Type componentType) : super(
+            /*Type*/ componentType);
+}
+
+method1(Class c, Type type, [o]) {
+  if (/*Class*/ c /*invoke: [Class]->bool*/ == null) {
+    if (/*dynamic*/ o /*invoke: [dynamic]->bool*/ != null) {
+      c = new Class(String);
+    }
+    /*Class*/ c;
+    print(/*Type*/ type /*invoke: [Type]->bool*/ == /*Class*/ c?.componentType);
+  }
+}
+
+method2(Class c, Type type, [o]) {
+  if (/*Class*/ c /*invoke: [Class]->bool*/ == null) {
+    if (/*dynamic*/ o /*invoke: [dynamic]->bool*/ != null) {
+      c = new SubClass(String);
+    }
+    /*Class*/ c;
+    print(/*Type*/ type /*invoke: [Type]->bool*/ == /*Class*/ c?.componentType);
+  }
+}
+
+method3(Class c, Type type, [o]) {
+  if (/*Class*/ c is SubClass) {
+    if (/*SubClass*/ c /*invoke: [SubClass]->bool*/ == null) {
+      if (/*dynamic*/ o /*invoke: [dynamic]->bool*/ != null) {
+        c = new SubClass(String);
+      }
+      /*SubClass*/ c;
+      print(/*Type*/ type /*invoke: [Type]->bool*/ ==
+          /*SubClass*/ c?.componentType);
+    }
+  }
+}
+
+main() {
+  method1(new Class(Object), Object);
+  method1(new Class(Object), Object, true);
+  method1(null, Object);
+  method1(null, Object, true);
+
+  method2(new Class(Object), Object);
+  method2(new Class(Object), Object, true);
+  method2(null, Object);
+  method2(null, Object, true);
+
+  method3(new Class(Object), Object);
+  method3(new Class(Object), Object, true);
+  method3(null, Object);
+  method3(null, Object, true);
+}

pkg/compiler/test/static_type/type_promotion_data/issue42281.dart

@@ -0,0 +1,65 @@
+// Copyright (c) 2020, 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.
+
+class Class {
+  final Type componentType;
+
+  Class(this.componentType);
+}
+
+class SubClass extends Class {
+  SubClass(Type componentType) : super(/*{}*/ componentType);
+}
+
+method1(Class c, Type type, [o]) {
+  if (/*{}*/ c == null) {
+    if (/*{c:[{false:Class}|Class]}*/ o != null) {
+      c = new Class(String);
+    }
+    /*{}*/ c;
+    print(/*{}*/ type == /*{}*/ c?.componentType);
+  }
+}
+
+method2(Class c, Type type, [o]) {
+  if (/*{}*/ c == null) {
+    if (/*{c:[{false:Class}|Class]}*/ o != null) {
+      c = new SubClass(String);
+    }
+    /*{}*/ c;
+    print(/*{}*/ type == /*{}*/ c?.componentType);
+  }
+}
+
+method3(Class c, Type type, [o]) {
+  if (/*{}*/ c is SubClass) {
+    if (/*{c:[{true:SubClass}|SubClass]}*/ c == null) {
+      if (/*{c:[{true:SubClass,false:Class}|SubClass,Class]}*/ o != null) {
+        c = new SubClass(String);
+      }
+      /*{c:[{true:SubClass},{false:Class}|SubClass,Class]}*/ c;
+      print(
+          /*{c:[{true:SubClass},{false:Class}|SubClass,Class]}*/ type ==
+              /*{c:[{true:SubClass},{false:Class}|SubClass,Class]}*/ c
+                  ?.componentType);
+    }
+  }
+}
+
+main() {
+  method1(new Class(Object), Object);
+  method1(new Class(Object), Object, true);
+  method1(null, Object);
+  method1(null, Object, true);
+
+  method2(new Class(Object), Object);
+  method2(new Class(Object), Object, true);
+  method2(null, Object);
+  method2(null, Object, true);
+
+  method3(new Class(Object), Object);
+  method3(new Class(Object), Object, true);
+  method3(null, Object);
+  method3(null, Object, true);
+}

tests/dart2js/regress_42281_test.dart

@@ -0,0 +1,46 @@
+// Copyright (c) 2020, 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.
+
+class ComponentFactory<T> {
+  @pragma('dart2js:noInline')
+  Type get componentType => T;
+}
+
+var mm = {'String': String, 'int': int};
+var gf1 = ComponentFactory<int>();
+var gf2 = ComponentFactory<dynamic>();
+Map<String, ComponentFactory?> mf = {'RegExp': ComponentFactory<RegExp>()};
+
+ComponentFactory? test(String s, [Map<String, ComponentFactory>? mf2]) {
+  var f = mf[s];
+  if (f == null) {
+    var t = mm[s];
+    if (mf2 != null) f = mf2[s];
+    if (t != null && t != f?.componentType) {
+      print('not match $t');
+      f = gf2;
+    }
+  }
+  return f;
+}
+
+work() {
+  Map<String, ComponentFactory> mf2 = {'int': ComponentFactory<num>()};
+
+  test('String');
+  test('String', mf2);
+  test('int');
+  test('int', mf2);
+  test('RegExp');
+  test('RegExp', mf2);
+}
+
+main() {
+  try {
+    work();
+  } catch (e, st) {
+    print(e);
+    print(st);
+  }
+}

tests/dart2js_2/regress_42281_test.dart

@@ -0,0 +1,46 @@
+// Copyright (c) 2020, 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.
+
+class ComponentFactory<T> {
+  @pragma('dart2js:noInline')
+  Type get componentType => T;
+}
+
+var mm = {'String': String, 'int': int};
+var gf1 = ComponentFactory<int>();
+var gf2 = ComponentFactory<dynamic>();
+Map<String, ComponentFactory> mf = {'RegExp': ComponentFactory<RegExp>()};
+
+ComponentFactory test(String s, [Map<String, ComponentFactory> mf2]) {
+  var f = mf[s];
+  if (f == null) {
+    var t = mm[s];
+    if (mf2 != null) f = mf2[s];
+    if (t != null && t != f?.componentType) {
+      print('not match $t');
+      f = gf2;
+    }
+  }
+  return f;
+}
+
+work() {
+  Map<String, ComponentFactory> mf2 = {'int': ComponentFactory<num>()};
+
+  test('String');
+  test('String', mf2);
+  test('int');
+  test('int', mf2);
+  test('RegExp');
+  test('RegExp', mf2);
+}
+
+main() {
+  try {
+    work();
+  } catch (e, st) {
+    print(e);
+    print(st);
+  }
+}