[cfe] Resolve serialization mismatch due to variance computation

Change-Id: Id38c63f5bd659f21423d802fd6180aa04465712c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/123406
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Dmitry Stefantsov <dmitryas@google.com>

Author: Dmitry Stefantsov

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

@@ -137,6 +137,12 @@ abstract class LibraryBuilder implements ModifierBuilder {
 
   int finishTypeVariables(ClassBuilder object, TypeBuilder dynamicType);
 
+  /// Computes variances of type parameters on typedefs.
+  ///
+  /// The variance property of type parameters on typedefs is computed from the
+  /// use of the parameters in the right-hand side of the typedef definition.
+  int computeVariances() => 0;
+
   /// This method instantiates type parameters to their bounds in some cases
   /// where they were omitted by the programmer and not provided by the type
   /// inference.  The method returns the number of distinct type variables
@@ -351,6 +357,9 @@ abstract class LibraryBuilderImpl extends ModifierBuilderImpl
   @override
   int finishTypeVariables(ClassBuilder object, TypeBuilder dynamicType) => 0;
 
+  @override
+  int computeVariances() => 0;
+
   @override
   int computeDefaultTypes(TypeBuilder dynamicType, TypeBuilder bottomType,
       ClassBuilder objectClass) {

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

@@ -256,6 +256,7 @@ class KernelTarget extends TargetImplementation {
       loader.computeLibraryScopes();
       setupTopAndBottomTypes();
       loader.resolveTypes();
+      loader.computeVariances();
       loader.computeDefaultTypes(dynamicType, bottomType, objectClassBuilder);
       List<SourceClassBuilder> myClasses =
           loader.checkSemantics(objectClassBuilder);

pkg/front_end/lib/src/fasta/kernel/type_algorithms.dart

@@ -27,6 +27,7 @@ import '../builder/class_builder.dart';
 import '../builder/formal_parameter_builder.dart';
 import '../builder/function_type_builder.dart';
 import '../builder/invalid_type_declaration_builder.dart';
+import '../builder/library_builder.dart';
 import '../builder/named_type_builder.dart';
 import '../builder/nullability_builder.dart';
 import '../builder/type_alias_builder.dart';
@@ -44,21 +45,27 @@ import '../fasta_codes.dart'
         templateBoundIssueViaCycleNonSimplicity,
         templateBoundIssueViaLoopNonSimplicity,
         templateBoundIssueViaRawTypeWithNonSimpleBounds,
+        templateCyclicTypedef,
         templateNonSimpleBoundViaReference,
         templateNonSimpleBoundViaVariable;
 
 export 'package:kernel/ast.dart' show Variance;
 
+/// Initial value for "variance" that is to be computed by the compiler.
+const int pendingVariance = -1;
+
 // Computes the variance of a variable in a type.  The function can be run
 // before the types are resolved to compute variances of typedefs' type
 // variables.  For that case if the type has its declaration set to null and its
 // name matches that of the variable, it's interpreted as an occurrence of a
 // type variable.
-int computeVariance(TypeVariableBuilder variable, TypeBuilder type) {
+int computeVariance(TypeVariableBuilder variable, TypeBuilder type,
+    LibraryBuilder libraryBuilder) {
   if (type is NamedTypeBuilder) {
+    assert(type.declaration != null);
     TypeDeclarationBuilder declaration = type.declaration;
-    if (declaration == null || declaration is TypeVariableBuilder) {
-      if (type.name == variable.name) {
+    if (declaration is TypeVariableBuilder) {
+      if (declaration == variable) {
         return Variance.covariant;
       } else {
         return Variance.unrelated;
@@ -70,21 +77,46 @@ int computeVariance(TypeVariableBuilder variable, TypeBuilder type) {
           for (int i = 0; i < type.arguments.length; ++i) {
             result = Variance.meet(
                 result,
-                Variance.combine(declaration.cls.typeParameters[i].variance,
-                    computeVariance(variable, type.arguments[i])));
+                Variance.combine(
+                    declaration.cls.typeParameters[i].variance,
+                    computeVariance(
+                        variable, type.arguments[i], libraryBuilder)));
           }
         }
         return result;
       } else if (declaration is TypeAliasBuilder) {
         int result = Variance.unrelated;
+
         if (type.arguments != null) {
           for (int i = 0; i < type.arguments.length; ++i) {
+            const int visitMarker = -2;
+
+            TypeVariableBuilder declarationTypeVariable =
+                declaration.typeVariables[i];
+
+            if (declarationTypeVariable.variance == pendingVariance) {
+              declarationTypeVariable.variance = visitMarker;
+              int computedVariance = computeVariance(
+                  declarationTypeVariable, declaration.type, libraryBuilder);
+              declarationTypeVariable.variance = computedVariance;
+            } else if (declarationTypeVariable.variance == visitMarker) {
+              libraryBuilder.addProblem(
+                  templateCyclicTypedef.withArguments(declaration.name),
+                  declaration.charOffset,
+                  declaration.name.length,
+                  declaration.fileUri);
+              // Use [Variance.unrelated] for recovery.  The type with the
+              // cyclic dependency will be replaced with an [InvalidType]
+              // elsewhere.
+              declarationTypeVariable.variance = Variance.unrelated;
+            }
+
             result = Variance.meet(
                 result,
                 Variance.combine(
-                    computeVariance(variable, type.arguments[i]),
                     computeVariance(
-                        declaration.typeVariables[i], declaration.type)));
+                        variable, type.arguments[i], libraryBuilder),
+                    declarationTypeVariable.variance));
           }
         }
         return result;
@@ -93,8 +125,8 @@ int computeVariance(TypeVariableBuilder variable, TypeBuilder type) {
   } else if (type is FunctionTypeBuilder) {
     int result = Variance.unrelated;
     if (type.returnType != null) {
-      result =
-          Variance.meet(result, computeVariance(variable, type.returnType));
+      result = Variance.meet(
+          result, computeVariance(variable, type.returnType, libraryBuilder));
     }
     if (type.typeVariables != null) {
       for (TypeVariableBuilder typeVariable in type.typeVariables) {
@@ -103,7 +135,7 @@ int computeVariance(TypeVariableBuilder variable, TypeBuilder type) {
         // of [computeVariance] below is made to simply figure out if [variable]
         // occurs in the bound.
         if (typeVariable.bound != null &&
-            computeVariance(variable, typeVariable.bound) !=
+            computeVariance(variable, typeVariable.bound, libraryBuilder) !=
                 Variance.unrelated) {
           result = Variance.invariant;
         }
@@ -114,7 +146,7 @@ int computeVariance(TypeVariableBuilder variable, TypeBuilder type) {
         result = Variance.meet(
             result,
             Variance.combine(Variance.contravariant,
-                computeVariance(variable, formal.type)));
+                computeVariance(variable, formal.type, libraryBuilder)));
       }
     }
     return result;

pkg/front_end/lib/src/fasta/source/source_class_builder.dart

@@ -239,7 +239,7 @@ class SourceClassBuilder extends ClassBuilderImpl
     if (typeVariables == null || supertype == null) return supertype;
     Message message;
     for (int i = 0; i < typeVariables.length; ++i) {
-      int variance = computeVariance(typeVariables[i], supertype);
+      int variance = computeVariance(typeVariables[i], supertype, library);
       if (!Variance.greaterThanOrEqual(variance, typeVariables[i].variance)) {
         if (typeVariables[i].parameter.isLegacyCovariant) {
           message = templateInvalidTypeVariableInSupertype.withArguments(

pkg/front_end/lib/src/fasta/source/source_library_builder.dart

@@ -177,7 +177,8 @@ import '../kernel/type_algorithms.dart'
         computeVariance,
         findGenericFunctionTypes,
         getNonSimplicityIssuesForDeclaration,
-        getNonSimplicityIssuesForTypeVariables;
+        getNonSimplicityIssuesForTypeVariables,
+        pendingVariance;
 
 import '../loader.dart' show Loader;
 
@@ -1995,9 +1996,8 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       FunctionTypeBuilder type,
       int charOffset) {
     if (typeVariables != null) {
-      for (int i = 0; i < typeVariables.length; ++i) {
-        TypeVariableBuilder variable = typeVariables[i];
-        variable.variance = computeVariance(variable, type);
+      for (TypeVariableBuilder typeVariable in typeVariables) {
+        typeVariable.variance = pendingVariance;
       }
     }
     TypeAliasBuilder typedefBuilder = new TypeAliasBuilder(
@@ -2398,6 +2398,21 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
     return count;
   }
 
+  int computeVariances() {
+    int count = 0;
+    for (Builder declaration in libraryDeclaration.members.values) {
+      if (declaration is TypeAliasBuilder &&
+          declaration.typeVariablesCount > 0) {
+        for (TypeVariableBuilder typeParameter in declaration.typeVariables) {
+          typeParameter.variance =
+              computeVariance(typeParameter, declaration.type, this);
+          ++count;
+        }
+      }
+    }
+    return count;
+  }
+
   int computeDefaultTypes(TypeBuilder dynamicType, TypeBuilder bottomType,
       ClassBuilder objectClass) {
     int count = 0;

pkg/front_end/lib/src/fasta/source/source_loader.dart

@@ -513,6 +513,16 @@ class SourceLoader extends Loader {
     ticker.logMs("Resolved $count type-variable bounds");
   }
 
+  void computeVariances() {
+    int count = 0;
+    builders.forEach((Uri uri, LibraryBuilder library) {
+      if (library.loader == this) {
+        count += library.computeVariances();
+      }
+    });
+    ticker.logMs("Computed variances of $count type variables");
+  }
+
   void computeDefaultTypes(TypeBuilder dynamicType, TypeBuilder bottomType,
       ClassBuilder objectClass) {
     int count = 0;

pkg/front_end/testcases/general/long_chain_of_typedefs.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2018, 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 for potentially slow compilation of long typedef dependency chains.
+
+typedef Foo01<X, Y, Z> = void Function(Null);
+typedef Foo02<X, Y, Z> = void Function(Foo01<X, Y, Z>);
+typedef Foo03<X, Y, Z> = void Function(Foo02<X, Y, Z>);
+typedef Foo04<X, Y, Z> = void Function(Foo03<X, Y, Z>);
+typedef Foo05<X, Y, Z> = void Function(Foo04<X, Y, Z>);
+typedef Foo06<X, Y, Z> = void Function(Foo05<X, Y, Z>);
+typedef Foo07<X, Y, Z> = void Function(Foo06<X, Y, Z>);
+typedef Foo08<X, Y, Z> = void Function(Foo07<X, Y, Z>);
+typedef Foo09<X, Y, Z> = void Function(Foo08<X, Y, Z>);
+typedef Foo10<X, Y, Z> = void Function(Foo09<X, Y, Z>);
+typedef Foo11<X, Y, Z> = void Function(Foo10<X, Y, Z>);
+typedef Foo12<X, Y, Z> = void Function(Foo11<X, Y, Z>);
+typedef Foo13<X, Y, Z> = void Function(Foo12<X, Y, Z>);
+typedef Foo14<X, Y, Z> = void Function(Foo13<X, Y, Z>);
+typedef Foo15<X, Y, Z> = void Function(Foo14<X, Y, Z>);
+typedef Foo16<X, Y, Z> = void Function(Foo15<X, Y, Z>);
+typedef Foo17<X, Y, Z> = void Function(Foo16<X, Y, Z>);
+typedef Foo18<X, Y, Z> = void Function(Foo17<X, Y, Z>);
+typedef Foo19<X, Y, Z> = void Function(Foo18<X, Y, Z>);
+typedef Foo20<X, Y, Z> = void Function(Foo19<X, Y, Z>);
+
+main() {}

pkg/front_end/testcases/general/long_chain_of_typedefs.dart.outline.expect

@@ -0,0 +1,26 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+typedef Foo01<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (core::Null?) →* void;
+typedef Foo02<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((core::Null?) →* void) →* void;
+typedef Foo03<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((core::Null?) →* void) →* void) →* void;
+typedef Foo04<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((core::Null?) →* void) →* void) →* void) →* void;
+typedef Foo05<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((core::Null?) →* void) →* void) →* void) →* void) →* void;
+typedef Foo06<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo07<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo08<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo09<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo10<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo11<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo12<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo13<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo14<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo15<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo16<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo17<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo18<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo19<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = (((((((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+typedef Foo20<unrelated X extends core::Object* = dynamic, unrelated Y extends core::Object* = dynamic, unrelated Z extends core::Object* = dynamic> = ((((((((((((((((((((core::Null?) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void) →* void;
+static method main() → dynamic
+  ;