suggest keywords for more expressions

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

Index: pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart b/pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart
index 5414bcc3fd644de18dcce4dfa1c6f4909af0d5fb..7a8763bd47b98c9a3c2d80621c55f8289d5d8ed8 100644
--- a/pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart
@@ -128,6 +128,11 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
   }
 
   @override
+  visitExpression(Expression node) {
+    _addExpressionKeywords(node);
+  }
+
+  @override
   visitExpressionFunctionBody(ExpressionFunctionBody node) {
     if (entity == node.expression) {
       _addExpressionKeywords(node);
@@ -199,6 +204,25 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
   }
 
   @override
+  visitPrefixedIdentifier(PrefixedIdentifier node) {
+    if (entity != node.identifier) {
+      _addExpressionKeywords(node);
+    }
+  }
+
+  @override
+  visitReturnStatement(ReturnStatement node) {
+    if (entity == node.expression) {
+      _addExpressionKeywords(node);
+    }
+  }
+
+  @override
+  visitStringLiteral(StringLiteral node) {
+    // ignored
+  }
+
+  @override
   visitSwitchStatement(SwitchStatement node) {
     if (entity == node.expression) {
       _addExpressionKeywords(node);