[cfe] Thread nullability modifiers for some InterfaceTypes in outline

Closes flutter#38212.

Bug: http://dartbug.com/38212

Change-Id: I4127a1db46a932bd298f82053f58834b60fd4cbb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/115370
Commit-Queue: Dmitry Stefantsov <dmitryas@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/front_end/lib/src/fasta/builder/builder.dart

@@ -55,6 +55,8 @@ export 'name_iterator.dart' show NameIterator;
 
 export 'named_type_builder.dart' show NamedTypeBuilder;
 
+export 'nullability_builder.dart' show NullabilityBuilder;
+
 export 'prefix_builder.dart' show PrefixBuilder;
 
 export 'type_alias_builder.dart' show TypeAliasBuilder;

pkg/front_end/lib/src/fasta/builder/builtin_type_builder.dart

@@ -4,7 +4,7 @@
 
 library fasta.builtin_type_builder;
 
-import 'package:kernel/ast.dart' show DartType;
+import 'package:kernel/ast.dart' show DartType, Nullability;
 
 import 'builder.dart' show LibraryBuilder, TypeBuilder, TypeDeclarationBuilder;
 
@@ -15,11 +15,15 @@ abstract class BuiltinTypeBuilder extends TypeDeclarationBuilder {
       String name, this.type, LibraryBuilder compilationUnit, int charOffset)
       : super(null, 0, name, compilationUnit, charOffset);
 
-  DartType buildType(LibraryBuilder library, List<TypeBuilder> arguments) =>
-      type;
+  DartType buildType(LibraryBuilder library, Nullability nullability,
+      List<TypeBuilder> arguments) {
+    // TODO(dmitryas): Use [nullability].
+    return type;
+  }
 
-  DartType buildTypesWithBuiltArguments(
-      LibraryBuilder library, List<DartType> arguments) {
+  DartType buildTypesWithBuiltArguments(LibraryBuilder library,
+      Nullability nullability, List<DartType> arguments) {
+    // TODO(dmitryas): Use [nullability].
     return type;
   }
 

pkg/front_end/lib/src/fasta/builder/class_builder.dart

@@ -21,6 +21,7 @@ import 'package:kernel/ast.dart'
         Member,
         MethodInvocation,
         Name,
+        Nullability,
         Procedure,
         ProcedureKind,
         RedirectingFactoryConstructor,
@@ -407,10 +408,12 @@ abstract class ClassBuilder extends DeclarationBuilder {
   InterfaceType get thisType => cls.thisType;
 
   /// [arguments] have already been built.
-  InterfaceType buildTypesWithBuiltArguments(
-      LibraryBuilder library, List<DartType> arguments) {
+  InterfaceType buildTypesWithBuiltArguments(LibraryBuilder library,
+      Nullability nullability, List<DartType> arguments) {
     assert(arguments == null || cls.typeParameters.length == arguments.length);
-    return arguments == null ? cls.rawType : new InterfaceType(cls, arguments);
+    return arguments == null
+        ? cls.rawType
+        : new InterfaceType(cls, arguments, nullability);
   }
 
   @override
@@ -455,9 +458,10 @@ abstract class ClassBuilder extends DeclarationBuilder {
   }
 
   /// If [arguments] are null, the default types for the variables are used.
-  InterfaceType buildType(LibraryBuilder library, List<TypeBuilder> arguments) {
+  InterfaceType buildType(LibraryBuilder library, Nullability nullability,
+      List<TypeBuilder> arguments) {
     return buildTypesWithBuiltArguments(
-        library, buildTypeArguments(library, arguments));
+        library, nullability, buildTypeArguments(library, arguments));
   }
 
   Supertype buildSupertype(

pkg/front_end/lib/src/fasta/builder/enum_builder.dart

@@ -4,7 +4,7 @@
 
 library fasta.enum_builder;
 
-import 'builder.dart' show ClassBuilder, MetadataBuilder;
+import 'builder.dart' show ClassBuilder, MetadataBuilder, NullabilityBuilder;
 
 import 'package:kernel/ast.dart'
     show
@@ -19,6 +19,7 @@ import 'package:kernel/ast.dart'
         IntLiteral,
         InterfaceType,
         ListLiteral,
+        Nullability,
         ProcedureKind,
         ReturnStatement,
         StaticGet,
@@ -107,15 +108,19 @@ class EnumBuilder extends SourceClassBuilder {
     assert(enumConstantInfos == null || enumConstantInfos.isNotEmpty);
     // TODO(ahe): These types shouldn't be looked up in scope, they come
     // directly from dart:core.
-    TypeBuilder intType = new NamedTypeBuilder("int", null);
-    TypeBuilder stringType = new NamedTypeBuilder("String", null);
-    NamedTypeBuilder objectType = new NamedTypeBuilder("Object", null);
+    TypeBuilder intType =
+        new NamedTypeBuilder("int", const NullabilityBuilder.omitted(), null);
+    TypeBuilder stringType = new NamedTypeBuilder(
+        "String", const NullabilityBuilder.omitted(), null);
+    NamedTypeBuilder objectType = new NamedTypeBuilder(
+        "Object", const NullabilityBuilder.omitted(), null);
     Class cls = new Class(name: name);
     Map<String, MemberBuilder> members = <String, MemberBuilder>{};
     Map<String, MemberBuilder> constructors = <String, MemberBuilder>{};
-    NamedTypeBuilder selfType = new NamedTypeBuilder(name, null);
-    TypeBuilder listType =
-        new NamedTypeBuilder("List", <TypeBuilder>[selfType]);
+    NamedTypeBuilder selfType =
+        new NamedTypeBuilder(name, const NullabilityBuilder.omitted(), null);
+    TypeBuilder listType = new NamedTypeBuilder(
+        "List", const NullabilityBuilder.omitted(), <TypeBuilder>[selfType]);
 
     /// metadata class E {
     ///   final int index;
@@ -258,7 +263,9 @@ class EnumBuilder extends SourceClassBuilder {
 
   TypeBuilder get mixedInType => null;
 
-  InterfaceType buildType(LibraryBuilder library, List<TypeBuilder> arguments) {
+  InterfaceType buildType(LibraryBuilder library, Nullability nullability,
+      List<TypeBuilder> arguments) {
+    // TODO(dmitryas): Use [nullability].
     return cls.rawType;
   }
 

pkg/front_end/lib/src/fasta/builder/extension_builder.dart

@@ -58,13 +58,14 @@ abstract class ExtensionBuilder extends DeclarationBuilder {
       fileUri);
 
   @override
-  DartType buildType(LibraryBuilder library, List<TypeBuilder> arguments) {
+  DartType buildType(LibraryBuilder library, Nullability nullability,
+      List<TypeBuilder> arguments) {
     throw new UnsupportedError("ExtensionBuilder.buildType is not supported.");
   }
 
   @override
-  DartType buildTypesWithBuiltArguments(
-      LibraryBuilder library, List<DartType> arguments) {
+  DartType buildTypesWithBuiltArguments(LibraryBuilder library,
+      Nullability nullability, List<DartType> arguments) {
     throw new UnsupportedError("ExtensionBuilder.buildTypesWithBuiltArguments "
         "is not supported.");
   }

pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart

@@ -4,7 +4,7 @@
 
 library fasta.invalid_type_builder;
 
-import 'package:kernel/ast.dart' show DartType, InvalidType;
+import 'package:kernel/ast.dart' show DartType, InvalidType, Nullability;
 
 import '../fasta_codes.dart' show LocatedMessage;
 
@@ -28,13 +28,14 @@ class InvalidTypeBuilder extends TypeDeclarationBuilder {
   @override
   InvalidType get target => const InvalidType();
 
-  DartType buildType(LibraryBuilder library, List<TypeBuilder> arguments) {
-    return buildTypesWithBuiltArguments(library, null);
+  DartType buildType(LibraryBuilder library, Nullability nullability,
+      List<TypeBuilder> arguments) {
+    return buildTypesWithBuiltArguments(library, null, null);
   }
 
   /// [Arguments] have already been built.
-  DartType buildTypesWithBuiltArguments(
-      LibraryBuilder library, List<DartType> arguments) {
+  DartType buildTypesWithBuiltArguments(LibraryBuilder library,
+      Nullability nullability, List<DartType> arguments) {
     if (!suppressMessage) {
       library.addProblem(message.messageObject, message.charOffset,
           message.length, message.uri,

pkg/front_end/lib/src/fasta/builder/library_builder.dart

@@ -32,6 +32,7 @@ import 'builder.dart'
         FieldBuilder,
         ModifierBuilder,
         NameIterator,
+        NullabilityBuilder,
         PrefixBuilder,
         Scope,
         ScopeBuilder,
@@ -272,6 +273,19 @@ abstract class LibraryBuilder extends ModifierBuilder {
   void buildOutlineExpressions() {}
 
   List<FieldBuilder> takeImplicitlyTypedFields() => null;
+
+  // TODO(dmitryas): Compute the predicate using the library version instead.
+  bool get isNonNullableByDefault => loader.target.enableNonNullable;
+
+  NullabilityBuilder computeNullabilityFromToken(bool markedAsNullable) {
+    if (!isNonNullableByDefault) {
+      return const NullabilityBuilder.legacy();
+    }
+    if (markedAsNullable) {
+      return const NullabilityBuilder.nullable();
+    }
+    return const NullabilityBuilder.omitted();
+  }
 }
 
 class LibraryLocalDeclarationIterator implements Iterator<Builder> {

pkg/front_end/lib/src/fasta/builder/named_type_builder.dart

@@ -31,6 +31,7 @@ import 'builder.dart'
         Builder,
         Identifier,
         LibraryBuilder,
+        NullabilityBuilder,
         PrefixBuilder,
         QualifiedName,
         Scope,
@@ -54,12 +55,15 @@ class NamedTypeBuilder extends TypeBuilder {
 
   List<TypeBuilder> arguments;
 
+  final NullabilityBuilder nullabilityBuilder;
+
   @override
   TypeDeclarationBuilder declaration;
 
-  NamedTypeBuilder(this.name, this.arguments);
+  NamedTypeBuilder(this.name, this.nullabilityBuilder, this.arguments);
 
-  NamedTypeBuilder.fromTypeDeclarationBuilder(this.declaration,
+  NamedTypeBuilder.fromTypeDeclarationBuilder(
+      this.declaration, this.nullabilityBuilder,
       [this.arguments])
       : this.name = declaration.name;
 
@@ -181,6 +185,7 @@ class NamedTypeBuilder extends TypeBuilder {
       t.printOn(buffer);
     }
     buffer.write(">");
+    nullabilityBuilder.writeNullabilityOn(buffer);
     return buffer;
   }
 
@@ -209,7 +214,8 @@ class NamedTypeBuilder extends TypeBuilder {
 
   DartType build(LibraryBuilder library) {
     assert(declaration != null, "Declaration has not been resolved on $this.");
-    return declaration.buildType(library, arguments);
+    return declaration.buildType(
+        library, nullabilityBuilder.build(library), arguments);
   }
 
   Supertype buildSupertype(
@@ -265,7 +271,8 @@ class NamedTypeBuilder extends TypeBuilder {
         i++;
       }
       if (arguments != null) {
-        return new NamedTypeBuilder(name, arguments)..bind(declaration);
+        return new NamedTypeBuilder(name, nullabilityBuilder, arguments)
+          ..bind(declaration);
       }
     }
     return this;
@@ -279,7 +286,8 @@ class NamedTypeBuilder extends TypeBuilder {
         clonedArguments[i] = arguments[i].clone(newTypes);
       }
     }
-    NamedTypeBuilder newType = new NamedTypeBuilder(name, clonedArguments);
+    NamedTypeBuilder newType =
+        new NamedTypeBuilder(name, nullabilityBuilder, clonedArguments);
     newTypes.add(newType);
     return newType;
   }

pkg/front_end/lib/src/fasta/builder/nullability_builder.dart

@@ -0,0 +1,84 @@
+// 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.
+
+import 'dart:core' hide MapEntry;
+import 'package:kernel/ast.dart';
+import '../kernel/body_builder.dart';
+import '../builder/builder.dart';
+import '../problems.dart';
+
+/// Represents the nullability modifiers encountered while parsing the types.
+///
+/// The syntactic nullability needs to be interpreted, that is, built, into the
+/// semantic nullability used on [DartType]s of Kernel.
+enum SyntacticNullability {
+  /// Used when the type is declared with '?' suffix after it.
+  nullable,
+
+  /// Used when the type is declared in an opted-out library.
+  legacy,
+
+  /// Used when the type is declared without any nullability suffixes.
+  omitted,
+}
+
+class NullabilityBuilder {
+  final SyntacticNullability _syntacticNullability;
+
+  const NullabilityBuilder.nullable()
+      : _syntacticNullability = SyntacticNullability.nullable;
+
+  const NullabilityBuilder.legacy()
+      : _syntacticNullability = SyntacticNullability.legacy;
+
+  const NullabilityBuilder.omitted()
+      : _syntacticNullability = SyntacticNullability.omitted;
+
+  /// Used temporarily in the places that need proper handling of NNBD features.
+  ///
+  /// Over time the uses of [NullabilityBuilder.pendingImplementation] should be
+  /// eliminated, and the constructor should be eventually removed.  Currently,
+  /// it redirects to [NullabilityBuilder.legacy] as a conservative safety
+  /// measure for the pre-NNBD code and as a visible reminder of the feature
+  /// implementation being in progress in the NNBD code.
+  // TODO(dmitryas): Remove this constructor.
+  const NullabilityBuilder.pendingImplementation() : this.legacy();
+
+  Nullability build(LibraryBuilder libraryBuilder, {Nullability ifOmitted}) {
+    // TODO(dmitryas): Ensure that either ifOmitted is set or libraryBuilder is
+    // provided;
+    //assert(libraryBuilder != null || ifOmitted != null);
+    ifOmitted ??= (libraryBuilder == null ? Nullability.legacy : null);
+
+    ifOmitted ??= libraryBuilder.isNonNullableByDefault
+        ? Nullability.nonNullable
+        : Nullability.legacy;
+    switch (_syntacticNullability) {
+      case SyntacticNullability.legacy:
+        return Nullability.legacy;
+      case SyntacticNullability.nullable:
+        return Nullability.nullable;
+      case SyntacticNullability.omitted:
+        return ifOmitted;
+    }
+    return unhandled("$_syntacticNullability", "buildNullability",
+        TreeNode.noOffset, noLocation);
+  }
+
+  void writeNullabilityOn(StringBuffer sb) {
+    switch (_syntacticNullability) {
+      case SyntacticNullability.legacy:
+        sb.write("*");
+        return;
+      case SyntacticNullability.nullable:
+        sb.write("?");
+        return;
+      case SyntacticNullability.omitted:
+        // Do nothing.
+        return;
+    }
+    unhandled("$_syntacticNullability", "writeNullabilityOn", TreeNode.noOffset,
+        noLocation);
+  }
+}

pkg/front_end/lib/src/fasta/builder/type_alias_builder.dart

@@ -10,6 +10,7 @@ import 'package:kernel/ast.dart'
         DynamicType,
         FunctionType,
         InvalidType,
+        Nullability,
         TypeParameter,
         Typedef,
         VariableDeclaration;
@@ -146,8 +147,9 @@ class TypeAliasBuilder extends TypeDeclarationBuilder {
   }
 
   /// [arguments] have already been built.
-  DartType buildTypesWithBuiltArguments(
-      LibraryBuilder library, List<DartType> arguments) {
+  DartType buildTypesWithBuiltArguments(LibraryBuilder library,
+      Nullability nullability, List<DartType> arguments) {
+    // TODO(dmitryas): Use [nullability].
     DartType thisType = buildThisType(library);
     if (const DynamicType() == thisType) return thisType;
     FunctionType result = thisType;
@@ -202,14 +204,15 @@ class TypeAliasBuilder extends TypeDeclarationBuilder {
   int get typeVariablesCount => typeVariables?.length ?? 0;
 
   @override
-  DartType buildType(LibraryBuilder library, List<TypeBuilder> arguments) {
+  DartType buildType(LibraryBuilder library, Nullability nullability,
+      List<TypeBuilder> arguments) {
     DartType thisType = buildThisType(library);
     if (thisType is InvalidType) return thisType;
     FunctionType result = thisType;
     if (typedef.typeParameters.isEmpty && arguments == null) return result;
     // Otherwise, substitute.
     return buildTypesWithBuiltArguments(
-        library, buildTypeArguments(library, arguments));
+        library, nullability, buildTypeArguments(library, arguments));
   }
 }