[kernel] Use Never as static type for throw/rethrow

Change-Id: Iba61a834827747e656a6dc14d73ee152f66864cd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127882
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

Author: johnniwinther

pkg/front_end/lib/src/testing/id_extractor.dart

@@ -484,6 +484,18 @@ abstract class DataExtractor<T> extends Visitor with DataRegistry<T> {
     super.visitStaticInvocation(node);
   }
 
+  @override
+  visitThrow(Throw node) {
+    computeForNode(node, computeDefaultNodeId(node));
+    super.visitThrow(node);
+  }
+
+  @override
+  visitRethrow(Rethrow node) {
+    computeForNode(node, computeDefaultNodeId(node));
+    super.visitRethrow(node);
+  }
+
   @override
   visitAsExpression(AsExpression node) {
     if (node.isTypeError) {

pkg/front_end/test/spell_checking_list_common.txt

@@ -2412,6 +2412,7 @@ resynthesize
 retain
 retained
 rethrow
+rethrowing
 retired
 retrieve
 retrieved

pkg/front_end/test/static_types/data/throw.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2019, 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.
+
+/*cfe|dart2js.library: nnbd=false*/
+/*cfe:nnbd.library: nnbd=true*/
+
+throwing() {
+  /*cfe|dart2js.<bottom>*/
+  /*cfe:nnbd.Never*/
+  throw
+      /*cfe|dart2js.String*/
+      /*cfe:nnbd.String!*/
+      'foo';
+}
+
+rethrowing() {
+  try {} catch (_) {
+    /*cfe|dart2js.<bottom>*/
+    /*cfe:nnbd.Never*/
+    rethrow;
+  }
+}

pkg/kernel/lib/ast.dart

@@ -4156,7 +4156,10 @@ class ThisExpression extends Expression {
 }
 
 class Rethrow extends Expression {
-  DartType getStaticType(StaticTypeContext context) => const BottomType();
+  DartType getStaticType(StaticTypeContext context) =>
+      context.isNonNullableByDefault
+          ? const NeverType(Nullability.nonNullable)
+          : const BottomType();
 
   R accept<R>(ExpressionVisitor<R> v) => v.visitRethrow(this);
   R accept1<R, A>(ExpressionVisitor1<R, A> v, A arg) =>
@@ -4173,7 +4176,10 @@ class Throw extends Expression {
     expression?.parent = this;
   }
 
-  DartType getStaticType(StaticTypeContext context) => const BottomType();
+  DartType getStaticType(StaticTypeContext context) =>
+      context.isNonNullableByDefault
+          ? const NeverType(Nullability.nonNullable)
+          : const BottomType();
 
   R accept<R>(ExpressionVisitor<R> v) => v.visitThrow(this);
   R accept1<R, A>(ExpressionVisitor1<R, A> v, A arg) => v.visitThrow(this, arg);

pkg/kernel/lib/type_environment.dart

@@ -714,6 +714,10 @@ class StaticTypeContext {
   ///
   /// For opt out libraries this is [Nullability.legacy].
   Nullability get nullable => _library.nullable;
+
+  /// Return `true` if the current library is opted in to non-nullable by
+  /// default.
+  bool get isNonNullableByDefault => _library.isNonNullableByDefault;
 }
 
 /// Implementation of [StaticTypeContext] that update its state when entering
@@ -792,6 +796,9 @@ class _FlatStatefulStaticTypeContext extends StatefulStaticTypeContext {
   @override
   Nullability get nullable => _library?.nullable;
 
+  @override
+  bool get isNonNullableByDefault => _library.isNonNullableByDefault;
+
   /// Updates the [nonNullable] and [thisType] to match static type context for
   /// the member [node].
   ///
@@ -876,6 +883,9 @@ class _StackedStatefulStaticTypeContext extends StatefulStaticTypeContext {
   @override
   Nullability get nullable => _library?.nullable;
 
+  @override
+  bool get isNonNullableByDefault => _library?.isNonNullableByDefault;
+
   /// Updates the [library] and [thisType] to match static type context for
   /// the member [node].
   ///