[DAS] Fixes pattern variable with multiple declarations highlight

Bug: https://github.com/dart-lang/sdk/issues/60398
Change-Id: Ifd7c29db38bb2ee048d2b7d0de1e050e1e3e9bc2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/417964
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Auto-Submit: Felipe Morschel <git@fmorschel.dev>
Reviewed-by: Phil Quitslund <pquitslund@google.com>

pkg/analysis_server/lib/src/domains/analysis/occurrences_dart.dart

@@ -100,7 +100,11 @@ class DartUnitOccurrencesComputerVisitor extends RecursiveAstVisitor<void> {
 
   @override
   void visitDeclaredVariablePattern(DeclaredVariablePattern node) {
-    _addOccurrence(node.declaredElement2!, node.name);
+    if (node.declaredElement2 case BindPatternVariableElement2(:var join2?)) {
+      _addOccurrence(join2.baseElement, node.name);
+    } else {
+      _addOccurrence(node.declaredElement2!, node.name);
+    }
 
     super.visitDeclaredVariablePattern(node);
   }

pkg/analysis_server/test/analysis/notification_occurrences_test.dart

@@ -576,6 +576,18 @@ String f(int char) {
       ''');
   }
 
+  Future<void> test_patternVariable_ifCase_logicalOr() async {
+    await assertOccurrences(kind: ElementKind.LOCAL_VARIABLE, '''
+void f(Object? x) {
+  if (x case int /*[0*/test/*0]*/ || [int /*[1*/test/*1]*/] when /*[2*/test/*2]*/ > 0) {
+    /*[3*/test/*3]*/;
+    /*[4*/test/*4]*/ = 1;
+    /*[5*/test/*5]*/ += 2;
+  }
+}
+''');
+  }
+
   Future<void> test_prefix() async {
     await assertOccurrences(kind: ElementKind.PREFIX, '''
 import '' as /*[0*/p/*0]*/;