Suggest 'is' in 'if (x is^)'.

pkg/analysis_server/lib/src/services/completion/dart/keyword_contributor.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/keyword_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/keyword_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/keyword_contributor.dart
index a79bb40a566e4318400067b31087c8377436a5c1..6d69c59466253ed66737aeab4e5f4da0d9cd1c85 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/keyword_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/keyword_contributor.dart
@@ -260,7 +260,11 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
 
   @override
   visitIfStatement(IfStatement node) {
-    if (entity == node.thenStatement) {
+    if (_isPreviousTokenSynthetic(entity, TokenType.CLOSE_PAREN)) {
+      // Actual: if (x i^)
+      // Parsed: if (x) i^
+      _addSuggestion(Keyword.IS, DART_RELEVANCE_HIGH);
+    } else if (entity == node.thenStatement) {
       _addStatementKeywords(node);
     } else if (entity == node.condition) {
       _addExpressionKeywords(node);