Deprecate ImportElement.prefixOffset

Change-Id: I74441b4c060c326b68c446b2483d6509dd2b2970
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/201663
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/analysis_server/lib/src/services/refactoring/rename_import.dart b/pkg/analysis_server/lib/src/services/refactoring/rename_import.dart
index db58a6d..2dfbd42 100644
--- a/pkg/analysis_server/lib/src/services/refactoring/rename_import.dart
+++ b/pkg/analysis_server/lib/src/services/refactoring/rename_import.dart
@@ -60,7 +60,7 @@
         var node = _findNode();
         if (node != null) {
           var uriEnd = node.uri.end;
-          var prefixEnd = element.prefixOffset + prefix.nameLength;
+          var prefixEnd = prefix.nameOffset + prefix.nameLength;
           edit = newSourceEdit_range(
               range.startOffsetEndOffset(uriEnd, prefixEnd), '');
         }
@@ -72,7 +72,7 @@
             edit = newSourceEdit_range(SourceRange(uriEnd, 0), ' as $newName');
           }
         } else {
-          var offset = element.prefixOffset;
+          var offset = prefix.nameOffset;
           var length = prefix.nameLength;
           edit = newSourceEdit_range(SourceRange(offset, length), newName);
         }
diff --git a/pkg/analyzer/CHANGELOG.md b/pkg/analyzer/CHANGELOG.md
index 2dd64a6..6853504 100644
--- a/pkg/analyzer/CHANGELOG.md
+++ b/pkg/analyzer/CHANGELOG.md
@@ -2,6 +2,7 @@
 * Added `StringInterpolation.firstString` and `lastString`, to express
   explicitly  that there are always (possibly empty) strings as the first
   and the last elements of an interpolation.
+* Deprecated `ImportElement.prefixOffset`, use `prefix.nameOffset` instead.
 
 ## 1.7.0
 * Require `meta: ^1.4.0`.
diff --git a/pkg/analyzer/lib/dart/element/element.dart b/pkg/analyzer/lib/dart/element/element.dart
index 596c1b6..eb07ad0 100644
--- a/pkg/analyzer/lib/dart/element/element.dart
+++ b/pkg/analyzer/lib/dart/element/element.dart
@@ -1284,6 +1284,7 @@
   /// Return the offset of the prefix of this import in the file that contains
   /// this import directive, or `-1` if this import is synthetic, does not have
   /// a prefix, or otherwise does not have an offset.
+  @Deprecated('Use prefix.nameOffset instead')
   int get prefixOffset;
 }
 
diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index e41c39c..b8b5942 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -3434,9 +3434,6 @@
   PrefixElement? prefix;
 
   @override
-  int prefixOffset = -1;
-
-  @override
   List<NamespaceCombinator> combinators = const [];
 
   /// The cached value of [namespace].
@@ -3474,6 +3471,10 @@
         NamespaceBuilder().createImportNamespaceForDirective(this);
   }
 
+  @Deprecated('Use prefix.nameOffset instead')
+  @override
+  int get prefixOffset => prefix?.nameOffset ?? -1;
+
   @override
   T? accept<T>(ElementVisitor<T> visitor) => visitor.visitImportElement(this);
 
diff --git a/pkg/analyzer/lib/src/summary2/informative_data.dart b/pkg/analyzer/lib/src/summary2/informative_data.dart
index 132f6fd..3e691ca 100644
--- a/pkg/analyzer/lib/src/summary2/informative_data.dart
+++ b/pkg/analyzer/lib/src/summary2/informative_data.dart
@@ -340,7 +340,6 @@
       (element, info) {
         element as ImportElementImpl;
         element.nameOffset = info.nameOffset;
-        element.prefixOffset = info.prefixOffset;
 
         var prefix = element.prefix;
         if (prefix is PrefixElementImpl) {
diff --git a/pkg/analyzer/test/src/summary/element_text.dart b/pkg/analyzer/test/src/summary/element_text.dart
index e3e0548..bd68a35 100644
--- a/pkg/analyzer/test/src/summary/element_text.dart
+++ b/pkg/analyzer/test/src/summary/element_text.dart
@@ -442,11 +442,12 @@
 
       writeIf(e.isDeferred, ' deferred');
 
-      if (e.prefix != null) {
+      var prefix = e.prefix;
+      if (prefix != null) {
         buffer.write(' as ');
-        writeName(e.prefix!);
+        writeName(prefix);
         if (withOffsets) {
-          buffer.write('(${e.prefixOffset})');
+          buffer.write('(${prefix.nameOffset})');
         }
       }