fix completions in indexed expression

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

Index: pkg/analysis_server/lib/src/services/completion/optype.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/optype.dart b/pkg/analysis_server/lib/src/services/completion/optype.dart
index ef2902bc63ca2e76bb71523df82c819643447cf6..7b06919ed2ab5c8b36f5693de26ce1da84377043 100644
--- a/pkg/analysis_server/lib/src/services/completion/optype.dart
+++ b/pkg/analysis_server/lib/src/services/completion/optype.dart
@@ -6,6 +6,7 @@ library services.completion.computer.dart.optype;
 
 import 'package:analysis_server/src/services/completion/completion_target.dart';
 import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/scanner.dart';
 
 /**
  * An [AstVisitor] for determining whether top level suggestions or invocation
@@ -247,6 +248,15 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
 
   @override
   void visitExpressionStatement(ExpressionStatement node) {
+    // Given f[], the parser drops the [] from the expression statement
+    // but the [] token is the CompletionTarget entity
+    if (entity is Token) {
+      Token token = entity;
+      if (token.lexeme == '[]' && offset == token.offset + 1) {
+        optype.includeReturnValueSuggestions = true;
+        optype.includeTypeNameSuggestions = true;
+      }
+    }
   }
 
   @override
@@ -307,6 +317,12 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
   }
 
   @override
+  void visitIndexExpression(IndexExpression node) {
+    optype.includeReturnValueSuggestions = true;
+    optype.includeTypeNameSuggestions = true;
+  }
+
+  @override
   void visitInstanceCreationExpression(InstanceCreationExpression node) {
     if (identical(entity, node.constructorName)) {
       optype.includeTypeNameSuggestions = true;