Issue 25034. Record only the target source's errors.

pkg/analyzer/test/generated/compile_time_error_code_test.dart

 // Copyright (c) 2014, 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.
 
 library engine.compile_time_error_code_test;
 
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/source_io.dart';
 
@@ skipping 1617 matching lines @@
 
 class A {}''');
     Source sourceB = addNamedSource(
         "/b.dart",
         r'''
 part of lib;
 
 class A {}''');
     computeLibrarySourceErrors(librarySource);
     assertErrors(sourceB, [CompileTimeErrorCode.DUPLICATE_DEFINITION]);
+    assertNoErrors(librarySource);
     verify([librarySource, sourceA, sourceB]);
   }
 
+  void test_duplicateDefinition_inPart() {
+    Source librarySource = addNamedSource(
+        "/lib.dart",
+        r'''
+library test;
+part 'a.dart';
+class A {}''');
+    Source sourceA = addNamedSource(
+        "/a.dart",
+        r'''
+part of test;
+class A {}''');
+    computeLibrarySourceErrors(librarySource);
+    assertErrors(sourceA, [CompileTimeErrorCode.DUPLICATE_DEFINITION]);
+    assertNoErrors(librarySource);
+    verify([librarySource, sourceA]);
+  }
+
   void test_duplicateDefinition_catch() {
     Source source = addSource(r'''
 main() {
   try {} catch (e, e) {}
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.DUPLICATE_DEFINITION]);
     verify([source]);
   }
 
@@ skipping 4582 matching lines @@
         source, [CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_OPERATOR]);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "");
     _check_wrongNumberOfParametersForOperator(name, "a, b");
   }
 }