Re-land "Fix analyzer/FE integration of assignments to ambiguous types."

This reverts commit 9f79588.

Change-Id: I485d0722fe8651212660dc961ae9271045ee0c54
Reviewed-on: https://dart-review.googlesource.com/71100
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart

@@ -903,6 +903,23 @@ void f(num x, int y) {
     assertElement(yRef, findElement.parameter('y'));
   }
 
+  test_assign_to_ambiguous_type() async {
+    provider.newFile(_p('/test/lib/a.dart'), 'class C {}');
+    provider.newFile(_p('/test/lib/b.dart'), 'class C {}');
+    addTestFile('''
+import 'a.dart';
+import 'b.dart';
+void f(int x) {
+  C = x;
+}
+''');
+    await resolveTestFile();
+
+    var xRef = findNode.simple('x;');
+    assertType(xRef, 'int');
+    assertElement(xRef, findElement.parameter('x'));
+  }
+
   test_assign_to_class() async {
     addTestFile('''
 class C {}

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

@@ -1332,9 +1332,11 @@ class KernelTypeUseGenerator extends KernelReadOnlyAccessGenerator
         helper.addProblemErrorIfConst(
             declaration.message.messageObject, offset, token.length);
       }
-      return new SyntheticExpressionJudgment(
+      return new UnresolvedVariableGetJudgment(
           new Throw(forest.literalString(declaration.message.message, token))
-            ..fileOffset = offset);
+            ..fileOffset = offset,
+          token.isSynthetic)
+        ..fileOffset = offset;
     } else {
       return forest.literalType(
           buildTypeWithBuiltArguments(null, nonInstanceAccessIsError: true),

tests/language_2/language_2_analyzer.status

@@ -155,7 +155,6 @@ issue31596_super_test/01: CompileTimeError # Front end fails to skip forwarding
 issue31596_super_test/03: CompileTimeError # Front end fails to skip forwarding stubs when resolving super calls
 label5_test/01: Crash # Error recovery in method body (illegal jump target)
 label6_test/03: Crash # Error recovery in method body (illegal jump target)
-library_ambiguous_test/00: Crash # Error recovery in method body (ambiguous imported name)
 library_test/01: Crash # Issue 33686 - No core library found
 list_literal_negative_test: Crash # Error recovery in method body (malformed constructor invocation)
 list_literal_syntax_test/06: Crash
@@ -251,7 +250,6 @@ parameter_metadata_test/04: Crash # Poor handling of annotation inside function-
 parser_quirks_test: CompileTimeError # Issue 34047
 part_of_multiple_libs_test/01: Crash # Poor handling of part file used by multiple libs
 part_refers_to_core_library_test/01: Crash # Issue 33686 - No core library found
-prefix_import_collision_test/01: Crash # Error recovery in method body (ambiguous imported name)
 prefix_shadow_test/01: Crash # Error recovery in method body (attempt to use type variable as prefix)
 prefix_variable_collision_test/01: Crash # Issue 33686 - No core library found
 regress_20394_test/01: Crash # Error recovery in method body (error in super constructor call)