Elements. Deprecate PrefixElement.

Change-Id: Ib529b4e24cce53a7a6a6693c94dbc51ee8ba83f2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/418922
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/api.txt

@@ -3074,7 +3074,7 @@ package:analyzer/dart/element/element.dart:
     redirectedConstructor (getter: ConstructorElement?)
     returnType (getter: InterfaceType)
     superConstructor (getter: ConstructorElement?)
-  DeferredImportElementPrefix (class extends Object implements ImportElementPrefix):
+  DeferredImportElementPrefix (class extends Object implements ImportElementPrefix, deprecated):
     new (constructor: DeferredImportElementPrefix Function())
   DirectiveUri (class extends Object):
     new (constructor: DirectiveUri Function())
@@ -3326,7 +3326,7 @@ package:analyzer/dart/element/element.dart:
   HideElementCombinator (class extends Object implements NamespaceCombinator):
     new (constructor: HideElementCombinator Function())
     hiddenNames (getter: List<String>)
-  ImportElementPrefix (class extends Object):
+  ImportElementPrefix (class extends Object, deprecated):
     new (constructor: ImportElementPrefix Function())
     element (getter: PrefixElement)
   InstanceElement (class extends Object implements TypeDefiningElement, TypeParameterizedElement, deprecated):
@@ -3407,7 +3407,7 @@ package:analyzer/dart/element/element.dart:
     importKeywordOffset (getter: int)
     importedLibrary (getter: LibraryElement?)
     namespace (getter: Namespace)
-    prefix (getter: ImportElementPrefix?)
+    prefix (getter: ImportElementPrefix?, deprecated)
     uri (getter: DirectiveUri)
   LibraryLanguageVersion (class extends Object):
     new (constructor: LibraryLanguageVersion Function({required Version? override, required Version package}))
@@ -3462,7 +3462,7 @@ package:analyzer/dart/element/element.dart:
   PatternVariableElement (class extends Object implements LocalVariableElement, deprecated):
     new (constructor: PatternVariableElement Function())
     join (getter: JoinPatternVariableElement?)
-  PrefixElement (class extends Object implements _ExistingElement):
+  PrefixElement (class extends Object implements _ExistingElement, deprecated):
     new (constructor: PrefixElement Function())
     enclosingElement3 (getter: CompilationUnitElement, deprecated)
     imports (getter: List<LibraryImportElement>)

pkg/analyzer/lib/dart/element/element.dart

@@ -330,6 +330,7 @@ abstract class ConstructorElement
 /// [ImportElementPrefix] that is used together with `deferred`.
 ///
 /// Clients may not extend, implement or mix-in this class.
+@Deprecated('Use PrefixElement2 instead')
 abstract class DeferredImportElementPrefix implements ImportElementPrefix {}
 
 /// Meaning of a URI referenced in a directive.
@@ -1315,6 +1316,7 @@ abstract class HideElementCombinator implements NamespaceCombinator {
 /// Usage of a [PrefixElement] in an `import` directive.
 ///
 /// Clients may not extend, implement or mix-in this class.
+@Deprecated('Use PrefixElement2 instead')
 abstract class ImportElementPrefix {
   /// The prefix that was specified as part of the import directive, or `null`
   /// if there was no prefix specified.
@@ -1786,6 +1788,7 @@ abstract class LibraryImportElement implements _ExistingElement {
 
   /// The prefix that was specified as part of the import directive, or `null`
   /// if there was no prefix specified.
+  @Deprecated(elementModelDeprecationMsg)
   ImportElementPrefix? get prefix;
 
   /// The interpretation of the URI specified in the directive.
@@ -2018,6 +2021,7 @@ abstract class PatternVariableElement implements LocalVariableElement {
 /// A prefix used to import one or more libraries into another library.
 ///
 /// Clients may not extend, implement or mix-in this class.
+@Deprecated('Use PrefixElement2 instead')
 abstract class PrefixElement implements _ExistingElement {
   @Deprecated(elementModelDeprecationMsg)
   @override

pkg/analyzer/lib/src/dart/element/element.dart

@@ -1949,7 +1949,9 @@ class DefaultSuperFormalParameterElementImpl
 }
 
 class DeferredImportElementPrefixImpl extends ImportElementPrefixImpl
-    implements DeferredImportElementPrefix {
+    implements
+        // ignore:deprecated_member_use_from_same_package
+        DeferredImportElementPrefix {
   DeferredImportElementPrefixImpl({
     required super.element,
   });
@@ -5547,7 +5549,10 @@ class HideElementCombinatorImpl implements HideElementCombinator {
   }
 }
 
-class ImportElementPrefixImpl implements ImportElementPrefix {
+class ImportElementPrefixImpl
+    implements
+        // ignore:deprecated_member_use_from_same_package
+        ImportElementPrefix {
   @override
   final PrefixElementImpl element;
 
@@ -9766,8 +9771,10 @@ class PatternVariableElementImpl2 extends LocalVariableElementImpl2
   }
 }
 
-/// A concrete implementation of a [PrefixElement].
-class PrefixElementImpl extends _ExistingElementImpl implements PrefixElement {
+class PrefixElementImpl extends _ExistingElementImpl
+    implements
+        // ignore:deprecated_member_use_from_same_package
+        PrefixElement {
   /// The scope of this prefix, `null` if not set yet.
   PrefixScope? _scope;
 

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

@@ -196,17 +196,19 @@ class DuplicateDefinitionVerifier {
     }
 
     var libraryDeclarations = _currentLibrary.libraryDeclarations;
-    for (var importPrefix in fragment.libraryImportPrefixes) {
-      var name = importPrefix.name;
-      if (libraryDeclarations.withName(name) case var existing?) {
-        _errorReporter.reportError(
-          _diagnosticFactory.duplicateDefinition(
-            CompileTimeErrorCode.PREFIX_COLLIDES_WITH_TOP_LEVEL_MEMBER,
-            importPrefix.asElement2,
-            existing,
-            [name],
-          ),
-        );
+    for (var importPrefix in fragment.prefixes) {
+      var name = importPrefix.name3;
+      if (name != null) {
+        if (libraryDeclarations.withName(name) case var existing?) {
+          _errorReporter.reportError(
+            _diagnosticFactory.duplicateDefinition(
+              CompileTimeErrorCode.PREFIX_COLLIDES_WITH_TOP_LEVEL_MEMBER,
+              importPrefix,
+              existing,
+              [name],
+            ),
+          );
+        }
       }
     }
 

pkg/analyzer/lib/src/utilities/extensions/element.dart

@@ -595,18 +595,6 @@ extension PatternVariableElementImplExtension on PatternVariableElementImpl {
   }
 }
 
-extension PrefixElement2Extension on PrefixElement2 {
-  PrefixElement get asElement {
-    return (this as PrefixElementImpl2).asElement;
-  }
-}
-
-extension PrefixElementExtension on PrefixElement {
-  PrefixElement2 get asElement2 {
-    return (this as PrefixElementImpl).element2;
-  }
-}
-
 extension PropertyAccessorElement2OrMemberExtension
     on PropertyAccessorElement2OrMember {
   PropertyAccessorElementOrMember get asElement {