[cfe] Handle unforseen type parameter intersections

Closes #42089

Change-Id: Ifb0dc0073e004051ae40aed51db24b0d4b10f50d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/152646
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

pkg/front_end/test/spell_checking_list_code.txt

@@ -53,6 +53,7 @@ arises
 arising
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+artifacts
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@@ -894,6 +895,7 @@ repeating
 replacements
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+replicated
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pkg/front_end/testcases/nnbd/issue42089.dart

@@ -0,0 +1,12 @@
+// 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.
+
+test<X>(X? x) {
+  if (x is String?) {
+    Object o = x;
+    o = x;
+  }
+}
+
+main() {}

pkg/front_end/testcases/nnbd/issue42089.dart.outline.expect

@@ -0,0 +1,8 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static method test<X extends core::Object? = dynamic>(self::test::X? x) → dynamic
+  ;
+static method main() → dynamic
+  ;

pkg/front_end/testcases/nnbd/issue42089.dart.strong.expect

@@ -0,0 +1,30 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     Object o = x;
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     o = x;
+//         ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test<X extends core::Object? = dynamic>(self::test::X? x) → dynamic {
+  if(x is{ForNonNullableByDefault} core::String?) {
+    core::Object o = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    Object o = x;
+               ^" in x{self::test::X? & core::String? /* '?' & '?' = '?' */} as{TypeError,ForNonNullableByDefault} core::Object;
+    o = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    o = x;
+        ^" in x{self::test::X? & core::String? /* '?' & '?' = '?' */} as{TypeError,ForNonNullableByDefault} core::Object;
+  }
+}
+static method main() → dynamic {}

pkg/front_end/testcases/nnbd/issue42089.dart.strong.transformed.expect

@@ -0,0 +1,30 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     Object o = x;
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     o = x;
+//         ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test<X extends core::Object? = dynamic>(self::test::X? x) → dynamic {
+  if(x is{ForNonNullableByDefault} core::String?) {
+    core::Object o = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    Object o = x;
+               ^" in let self::test::X? & core::String? /* '?' & '?' = '?' */ #t2 = x{self::test::X? & core::String? /* '?' & '?' = '?' */} in #t2.==(null) ?{core::Object} #t2 as{TypeError,ForNonNullableByDefault} core::Object : #t2{core::Object};
+    o = let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    o = x;
+        ^" in let self::test::X? & core::String? /* '?' & '?' = '?' */ #t4 = x{self::test::X? & core::String? /* '?' & '?' = '?' */} in #t4.==(null) ?{core::Object} #t4 as{TypeError,ForNonNullableByDefault} core::Object : #t4{core::Object};
+  }
+}
+static method main() → dynamic {}

pkg/front_end/testcases/nnbd/issue42089.dart.textual_outline.expect

@@ -0,0 +1,2 @@
+test<X>(X? x) {}
+main() {}

pkg/front_end/testcases/nnbd/issue42089.dart.textual_outline_modelled.expect

@@ -0,0 +1,2 @@
+main() {}
+test<X>(X? x) {}

pkg/front_end/testcases/nnbd/issue42089.dart.weak.expect

@@ -0,0 +1,30 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     Object o = x;
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     o = x;
+//         ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test<X extends core::Object? = dynamic>(self::test::X? x) → dynamic {
+  if(x is{ForNonNullableByDefault} core::String?) {
+    core::Object o = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    Object o = x;
+               ^" in x{self::test::X? & core::String? /* '?' & '?' = '?' */} as{TypeError,ForNonNullableByDefault} core::Object;
+    o = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    o = x;
+        ^" in x{self::test::X? & core::String? /* '?' & '?' = '?' */} as{TypeError,ForNonNullableByDefault} core::Object;
+  }
+}
+static method main() → dynamic {}

pkg/front_end/testcases/nnbd/issue42089.dart.weak.transformed.expect

@@ -0,0 +1,30 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     Object o = x;
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+//  - 'Object' is from 'dart:core'.
+//     o = x;
+//         ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test<X extends core::Object? = dynamic>(self::test::X? x) → dynamic {
+  if(x is{ForNonNullableByDefault} core::String?) {
+    core::Object o = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:7:16: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    Object o = x;
+               ^" in x{self::test::X? & core::String? /* '?' & '?' = '?' */};
+    o = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue42089.dart:8:9: Error: A value of type 'X?' can't be assigned to a variable of type 'Object'.
+ - 'Object' is from 'dart:core'.
+    o = x;
+        ^" in x{self::test::X? & core::String? /* '?' & '?' = '?' */};
+  }
+}
+static method main() → dynamic {}

pkg/front_end/testcases/nnbd_mixed/type_parameter_nullability.dart

@@ -0,0 +1,31 @@
+// 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.
+
+import 'type_parameter_nullability_lib.dart';
+
+class C<T extends num?, S, U> {
+  void promoteNullable(T? t) {
+    if (t is int) /* Creates T? & int! */ {
+      t;
+    }
+    if (t is int?) /* Creates T? & int? */ {
+      t;
+    }
+  }
+
+  void nullableAsUndetermined(S? s) {
+    s as U; /* Creates S? & U% */
+  }
+}
+
+main() {
+  var c = new C<num, num, num>();
+  c.promoteNullable(null);
+  c.promoteNullable(0);
+  c.nullableAsUndetermined(null);
+  c.nullableAsUndetermined(0);
+  var d = new D<num>();
+  d.promoteLegacy(null);
+  d.promoteLegacy(0);
+}

pkg/front_end/testcases/nnbd_mixed/type_parameter_nullability.dart.textual_outline.expect

@@ -0,0 +1,8 @@
+import 'type_parameter_nullability_lib.dart';
+
+class C<T extends num?, S, U> {
+  void promoteNullable(T? t) {}
+  void nullableAsUndetermined(S? s) {}
+}
+
+main() {}

pkg/front_end/testcases/nnbd_mixed/type_parameter_nullability.dart.textual_outline_modelled.expect

@@ -0,0 +1,8 @@
+import 'type_parameter_nullability_lib.dart';
+
+class C<T extends num?, S, U> {
+  void nullableAsUndetermined(S? s) {}
+  void promoteNullable(T? t) {}
+}
+
+main() {}

pkg/front_end/testcases/nnbd_mixed/type_parameter_nullability.dart.weak.expect

@@ -0,0 +1,58 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "type_parameter_nullability_lib.dart" as typ;
+
+import "org-dartlang-testcase:///type_parameter_nullability_lib.dart";
+
+class C<T extends core::num? = core::num?, S extends core::Object? = dynamic, U extends core::Object? = dynamic> extends core::Object {
+  synthetic constructor •() → self::C<self::C::T%, self::C::S%, self::C::U%>
+    : super core::Object::•()
+    ;
+  method promoteNullable(generic-covariant-impl self::C::T? t) → void {
+    if(t is{ForNonNullableByDefault} core::int) {
+      t{self::C::T? & core::int /* '?' & '!' = '!' */};
+    }
+    if(t is{ForNonNullableByDefault} core::int?) {
+      t{self::C::T? & core::int? /* '?' & '?' = '?' */};
+    }
+  }
+  method nullableAsUndetermined(generic-covariant-impl self::C::S? s) → void {
+    s as{ForNonNullableByDefault} self::C::U%;
+  }
+}
+static method main() → dynamic {
+  self::C<core::num, core::num, core::num> c = new self::C::•<core::num, core::num, core::num>();
+  c.{self::C::promoteNullable}(null);
+  c.{self::C::promoteNullable}(0);
+  c.{self::C::nullableAsUndetermined}(null);
+  c.{self::C::nullableAsUndetermined}(0);
+  typ::D<core::num> d = new typ::D::•<core::num>();
+  d.{typ::D::promoteLegacy}(null);
+  d.{typ::D::promoteLegacy}(0);
+}
+
+library;
+import self as typ;
+import "dart:core" as core;
+
+class D<T extends core::num* = core::num*> extends core::Object {
+  synthetic constructor •() → typ::D<typ::D::T*>*
+    : super core::Object::•()
+    ;
+  method promoteLegacy(generic-covariant-impl typ::D::T* t) → void {
+    if(t is core::int*) {
+      let final typ::D::T* & core::int* /* '*' & '*' = '*' */ #t1 = t{typ::D::T* & core::int* /* '*' & '*' = '*' */} in #t1.{core::num::==}(null) ?{core::bool*} null : #t1.{core::int::isEven};
+    }
+  }
+  abstract member-signature get _identityHashCode() → core::int*;
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*;
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*;
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*;
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*;
+  abstract member-signature operator ==(dynamic other) → core::bool*;
+  abstract member-signature get hashCode() → core::int*;
+  abstract member-signature method toString() → core::String*;
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic;
+  abstract member-signature get runtimeType() → core::Type*;
+}

pkg/front_end/testcases/nnbd_mixed/type_parameter_nullability.dart.weak.transformed.expect

@@ -0,0 +1,58 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "type_parameter_nullability_lib.dart" as typ;
+
+import "org-dartlang-testcase:///type_parameter_nullability_lib.dart";
+
+class C<T extends core::num? = core::num?, S extends core::Object? = dynamic, U extends core::Object? = dynamic> extends core::Object {
+  synthetic constructor •() → self::C<self::C::T%, self::C::S%, self::C::U%>
+    : super core::Object::•()
+    ;
+  method promoteNullable(generic-covariant-impl self::C::T? t) → void {
+    if(t is{ForNonNullableByDefault} core::int) {
+      t{self::C::T? & core::int /* '?' & '!' = '!' */};
+    }
+    if(t is{ForNonNullableByDefault} core::int?) {
+      t{self::C::T? & core::int? /* '?' & '?' = '?' */};
+    }
+  }
+  method nullableAsUndetermined(generic-covariant-impl self::C::S? s) → void {
+    s as{ForNonNullableByDefault} self::C::U%;
+  }
+}
+static method main() → dynamic {
+  self::C<core::num, core::num, core::num> c = new self::C::•<core::num, core::num, core::num>();
+  c.{self::C::promoteNullable}(null);
+  c.{self::C::promoteNullable}(0);
+  c.{self::C::nullableAsUndetermined}(null);
+  c.{self::C::nullableAsUndetermined}(0);
+  typ::D<core::num> d = new typ::D::•<core::num>();
+  d.{typ::D::promoteLegacy}(null);
+  d.{typ::D::promoteLegacy}(0);
+}
+
+library;
+import self as typ;
+import "dart:core" as core;
+
+class D<T extends core::num* = core::num*> extends core::Object {
+  synthetic constructor •() → typ::D<typ::D::T*>*
+    : super core::Object::•()
+    ;
+  method promoteLegacy(generic-covariant-impl typ::D::T* t) → void {
+    if(t is core::int*) {
+      let final typ::D::T* & core::int* /* '*' & '*' = '*' */ #t1 = t{typ::D::T* & core::int* /* '*' & '*' = '*' */} in #t1.{core::num::==}(null) ?{core::bool*} null : #t1.{core::int::isEven};
+    }
+  }
+  abstract member-signature get _identityHashCode() → core::int*;
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*;
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*;
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*;
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*;
+  abstract member-signature operator ==(dynamic other) → core::bool*;
+  abstract member-signature get hashCode() → core::int*;
+  abstract member-signature method toString() → core::String*;
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic;
+  abstract member-signature get runtimeType() → core::Type*;
+}

pkg/front_end/testcases/nnbd_mixed/type_parameter_nullability_lib.dart

@@ -0,0 +1,13 @@
+// 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.
+
+// @dart=2.6
+
+class D<T extends num> {
+  void promoteLegacy(T t) {
+    if (t is int) {
+      t?.isEven; // Creates T* & int!
+    }
+  }
+}