Add HintCode for duplicate shown/hidden names

Bug: https://github.com/dart-lang/sdk/issues/33182
Change-Id: Ibb82c44357bc59044340c6d8b1904c7815d19215
Reviewed-on: https://dart-review.googlesource.com/57161
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>

pkg/analyzer/lib/error/error.dart

@@ -257,6 +257,8 @@ const List<ErrorCode> errorCodeValues = const [
   HintCode.DEPRECATED_MIXIN_FUNCTION,
   HintCode.DIVISION_OPTIMIZATION,
   HintCode.DUPLICATE_IMPORT,
+  HintCode.DUPLICATE_HIDDEN_NAME,
+  HintCode.DUPLICATE_SHOWN_NAME,
   HintCode.FILE_IMPORT_INSIDE_LIB_REFERENCES_FILE_OUTSIDE,
   HintCode.FILE_IMPORT_OUTSIDE_LIB_REFERENCES_FILE_INSIDE,
   HintCode.GENERIC_METHOD_COMMENT,

pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart

@@ -334,6 +334,7 @@ class LibraryAnalyzer {
       verifier.addImports(unit);
       _usedImportedElementsList.forEach(verifier.removeUsedElements);
       verifier.generateDuplicateImportHints(errorReporter);
+      verifier.generateDuplicateShownHiddenNameHints(errorReporter);
       verifier.generateUnusedImportHints(errorReporter);
       verifier.generateUnusedShownNameHints(errorReporter);
     }

pkg/analyzer/lib/src/dart/error/hint_codes.dart

@@ -131,6 +131,22 @@ class HintCode extends ErrorCode {
       'DUPLICATE_IMPORT', "Duplicate import.",
       correction: "Try removing all but one import of the library.");
 
+  /**
+   * Duplicate hidden names.
+   */
+  static const HintCode DUPLICATE_HIDDEN_NAME =
+      const HintCode('DUPLICATE_HIDDEN_NAME', "Duplicate hidden name.",
+          correction: "Try removing the repeated name from the list of hidden "
+              "members.");
+
+  /**
+   * Duplicate shown names.
+   */
+  static const HintCode DUPLICATE_SHOWN_NAME =
+      const HintCode('DUPLICATE_SHOWN_NAME', "Duplicate shown name.",
+          correction: "Try removing the repeated name from the list of shown "
+              "members.");
+
   /**
    * It is a bad practice for a source file in a package "lib" directory
    * hierarchy to traverse outside that directory hierarchy. For example, a

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

@@ -4076,6 +4076,20 @@ class ImportsVerifier {
   final HashMap<ImportDirective, List<SimpleIdentifier>> _unusedShownNamesMap =
       new HashMap<ImportDirective, List<SimpleIdentifier>>();
 
+  /**
+   * A map of names that are hidden more than once.
+   */
+  final HashMap<NamespaceDirective, List<SimpleIdentifier>>
+      _duplicateHiddenNamesMap =
+      new HashMap<NamespaceDirective, List<SimpleIdentifier>>();
+
+  /**
+   * A map of names that are shown more than once.
+   */
+  final HashMap<NamespaceDirective, List<SimpleIdentifier>>
+      _duplicateShownNamesMap =
+      new HashMap<NamespaceDirective, List<SimpleIdentifier>>();
+
   void addImports(CompilationUnit node) {
     for (Directive directive in node.directives) {
       if (directive is ImportDirective) {
@@ -4105,6 +4119,9 @@ class ImportsVerifier {
         }
         _addShownNames(directive);
       }
+      if (directive is NamespaceDirective) {
+        _addDuplicateShownHiddenNames(directive);
+      }
     }
     if (_unusedImports.length > 1) {
       // order the list of unusedImports to find duplicates in faster than
@@ -4199,6 +4216,37 @@ class ImportsVerifier {
     });
   }
 
+  /**
+   * Report a [HintCode.DUPLICATE_SHOWN_HIDDEN_NAME] hint for each duplicate
+   * shown or hidden name.
+   *
+   * Only call this method after all of the compilation units have been visited
+   * by this visitor.
+   *
+   * @param errorReporter the error reporter used to report the set of
+   *          [HintCode.UNUSED_SHOWN_NAME] hints
+   */
+  void generateDuplicateShownHiddenNameHints(ErrorReporter reporter) {
+    _duplicateHiddenNamesMap.forEach(
+        (NamespaceDirective directive, List<SimpleIdentifier> identifiers) {
+      int length = identifiers.length;
+      for (int i = 0; i < length; i++) {
+        Identifier identifier = identifiers[i];
+        reporter.reportErrorForNode(
+            HintCode.DUPLICATE_HIDDEN_NAME, identifier, [identifier.name]);
+      }
+    });
+    _duplicateShownNamesMap.forEach(
+        (NamespaceDirective directive, List<SimpleIdentifier> identifiers) {
+      int length = identifiers.length;
+      for (int i = 0; i < length; i++) {
+        Identifier identifier = identifiers[i];
+        reporter.reportErrorForNode(
+            HintCode.DUPLICATE_SHOWN_NAME, identifier, [identifier.name]);
+      }
+    });
+  }
+
   /**
    * Remove elements from [_unusedImports] using the given [usedElements].
    */
@@ -4262,6 +4310,43 @@ class ImportsVerifier {
     }
   }
 
+  /**
+   * Add duplicate shown and hidden names from [directive] into
+   * [_duplicateHiddenNamesMap] and [_duplicateShownNamesMap].
+   */
+  void _addDuplicateShownHiddenNames(NamespaceDirective directive) {
+    if (directive.combinators == null) {
+      return;
+    }
+    for (Combinator combinator in directive.combinators) {
+      // Use a Set to find duplicates in faster than O(n^2) time.
+      Set<Element> identifiers = new Set<Element>();
+      if (combinator is HideCombinator) {
+        for (SimpleIdentifier name in combinator.hiddenNames) {
+          if (name.staticElement != null) {
+            if (!identifiers.add(name.staticElement)) {
+              // [name] is a duplicate.
+              List<SimpleIdentifier> duplicateNames = _duplicateHiddenNamesMap
+                  .putIfAbsent(directive, () => new List<SimpleIdentifier>());
+              duplicateNames.add(name);
+            }
+          }
+        }
+      } else if (combinator is ShowCombinator) {
+        for (SimpleIdentifier name in combinator.shownNames) {
+          if (name.staticElement != null) {
+            if (!identifiers.add(name.staticElement)) {
+              // [name] is a duplicate.
+              List<SimpleIdentifier> duplicateNames = _duplicateShownNamesMap
+                  .putIfAbsent(directive, () => new List<SimpleIdentifier>());
+              duplicateNames.add(name);
+            }
+          }
+        }
+      }
+    }
+  }
+
   /**
    * Lookup and return the [Namespace] from the [_namespaceMap].
    *

pkg/analyzer/lib/src/task/dart.dart

@@ -2836,6 +2836,7 @@ class GenerateHintsTask extends SourceBasedAnalysisTask {
       verifier.addImports(unit);
       usedImportedElementsList.forEach(verifier.removeUsedElements);
       verifier.generateDuplicateImportHints(errorReporter);
+      verifier.generateDuplicateShownHiddenNameHints(errorReporter);
       verifier.generateUnusedImportHints(errorReporter);
       verifier.generateUnusedShownNameHints(errorReporter);
     }

pkg/analyzer/test/generated/hint_code_test.dart

@@ -1241,6 +1241,32 @@ class B {}''');
     verify([source]);
   }
 
+  test_duplicateShownHiddenName_hidden() async {
+    Source source = addSource(r'''
+library L;
+export 'lib1.dart' hide A, B, A;''');
+    addNamedSource("/lib1.dart", r'''
+library lib1;
+class A {}
+class B {}''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [HintCode.DUPLICATE_HIDDEN_NAME]);
+    verify([source]);
+  }
+
+  test_duplicateShownHiddenName_shown() async {
+    Source source = addSource(r'''
+library L;
+export 'lib1.dart' show A, B, A;''');
+    addNamedSource("/lib1.dart", r'''
+library lib1;
+class A {}
+class B {}''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [HintCode.DUPLICATE_SHOWN_NAME]);
+    verify([source]);
+  }
+
   test_factory__expr_return_null_OK() async {
     Source source = addSource(r'''
 import 'package:meta/meta.dart';