Flow analysis: move into front_end.

This will allow it to be used by both the front end and the analyzer.

Change-Id: I3af67aaf3ad7ff2cca0cb245518570892ad473e9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/109986
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/analyzer/lib/src/dart/resolver/flow_analysis_visitor.dart

@@ -9,8 +9,8 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/dart/element/type_system.dart';
 import 'package:analyzer/src/dart/element/type.dart';
-import 'package:analyzer/src/dart/resolver/flow_analysis.dart';
 import 'package:analyzer/src/generated/variable_type_provider.dart';
+import 'package:front_end/src/fasta/flow_analysis/flow_analysis.dart';
 
 /// The helper for performing flow analysis during resolution.
 ///

pkg/analyzer/test/src/dart/resolution/test_all.dart

@@ -16,7 +16,6 @@ import 'export_test.dart' as export_;
 import 'extension_method_test.dart' as extension_method;
 import 'extension_override_test.dart' as extension_override;
 import 'flow_analysis_test.dart' as flow_analysis;
-import 'flow_analysis_unit_test.dart' as flow_analysis_unit;
 import 'for_element_test.dart' as for_element;
 import 'for_in_test.dart' as for_in;
 import 'function_expression_invocation_test.dart'
@@ -56,7 +55,6 @@ main() {
     extension_method.main();
     extension_override.main();
     flow_analysis.main();
-    flow_analysis_unit.main();
     for_element.main();
     for_in.main();
     function_expression_invocation.main();

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

@@ -95,7 +95,7 @@ class FlowAnalysis<Statement, Expression, Variable, Type> {
   /// erroneous code, it's possible that a variable might be used before its
   /// declaration.
   final Set<Variable> _referencedVariables =
-      _assertionsEnabled ? <Variable>{} : null;
+      _assertionsEnabled ? Set<Variable>() : null;
 
   factory FlowAnalysis(
     NodeOperations<Expression> nodeOperations,

pkg/front_end/test/fasta/flow_analysis/flow_analysis_test.dart

@@ -2,7 +2,7 @@
 // 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 'package:analyzer/src/dart/resolver/flow_analysis.dart';
+import 'package:front_end/src/fasta/flow_analysis/flow_analysis.dart';
 import 'package:test/test.dart';
 
 main() {
@@ -295,7 +295,7 @@ main() {
             .add(objectQVar)
             .add(intQVar)
             .promote(h, objectQVar, _Type('int'));
-        var s2 = s1.removePromotedAll({intQVar});
+        var s2 = s1.removePromotedAll([intQVar].toSet());
         expect(s2, same(s1));
       });
 
@@ -306,7 +306,7 @@ main() {
             .add(intQVar)
             .promote(h, objectQVar, _Type('int'))
             .promote(h, intQVar, _Type('int'));
-        var s2 = s1.removePromotedAll({intQVar});
+        var s2 = s1.removePromotedAll([intQVar].toSet());
         expect(s2.reachable, true);
         expect(s2.notAssigned, same(s1.notAssigned));
         _Type.allowComparisons(() {
@@ -320,12 +320,13 @@ main() {
         var h = _Harness();
         var reachable = State<_Var, _Type>(true);
         var unreachable = reachable.setReachable(false);
-        expect(reachable.restrict(h, emptySet, reachable, {}), same(reachable));
-        expect(reachable.restrict(h, emptySet, unreachable, {}),
+        expect(
+            reachable.restrict(h, emptySet, reachable, Set()), same(reachable));
+        expect(reachable.restrict(h, emptySet, unreachable, Set()),
             same(unreachable));
-        expect(unreachable.restrict(h, emptySet, unreachable, {}),
+        expect(unreachable.restrict(h, emptySet, unreachable, Set()),
             same(unreachable));
-        expect(unreachable.restrict(h, emptySet, unreachable, {}),
+        expect(unreachable.restrict(h, emptySet, unreachable, Set()),
             same(unreachable));
       });
 
@@ -338,7 +339,7 @@ main() {
         var s0 = State<_Var, _Type>(true).add(a).add(b).add(c).add(d);
         var s1 = s0.write(h, emptySet, a).write(h, emptySet, b);
         var s2 = s0.write(h, emptySet, a).write(h, emptySet, c);
-        var result = s1.restrict(h, emptySet, s2, {});
+        var result = s1.restrict(h, emptySet, s2, Set());
         expect(result.notAssigned.contains(a), false);
         expect(result.notAssigned.contains(b), false);
         expect(result.notAssigned.contains(c), false);
@@ -353,7 +354,8 @@ main() {
           var s0 = State<_Var, _Type>(true).add(x, assigned: true);
           var s1 = thisType == null ? s0 : s0.promote(h, x, _Type(thisType));
           var s2 = otherType == null ? s0 : s0.promote(h, x, _Type(otherType));
-          var result = s1.restrict(h, emptySet, s2, unsafe ? {x} : {});
+          var result =
+              s1.restrict(h, emptySet, s2, unsafe ? [x].toSet() : Set());
           if (expectedType == null) {
             expect(result.promoted, isNot(contains(x)));
           } else {

pkg/nnbd_migration/lib/src/decorated_type_operations.dart

@@ -4,7 +4,7 @@
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type_system.dart';
-import 'package:analyzer/src/dart/resolver/flow_analysis.dart';
+import 'package:front_end/src/fasta/flow_analysis/flow_analysis.dart';
 import 'package:nnbd_migration/src/decorated_type.dart';
 import 'package:nnbd_migration/src/node_builder.dart';