improve keyword suggestions - fixes #24016

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 9c32f9f14b0dad568c2906e07a38e514b123e95b..bdd477dd86a99f35506f6fd698aec846b3ff480c 100644
--- a/pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/keyword_contributor.dart
@@ -232,6 +232,15 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
   }
 
   @override
+  visitIsExpression(IsExpression node) {
+    if (entity == node.isOperator) {
+      _addSuggestion(Keyword.IS, DART_RELEVANCE_HIGH);
+    } else {
+      _addExpressionKeywords(node);
+    }
+  }
+
+  @override
   visitLibraryIdentifier(LibraryIdentifier node) {
     // no suggestions
   }
@@ -404,9 +413,14 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
     if (_inAsyncMethodOrFunction(node)) {
       _addSuggestion2(AWAIT);
     }
+    if (_inLoop(node)) {
+      _addSuggestions([Keyword.BREAK, Keyword.CONTINUE]);
+    }
+    if (_inSwitch(node)) {
+      _addSuggestions([Keyword.BREAK]);
+    }
     _addSuggestions([
       Keyword.ASSERT,
-      Keyword.CONTINUE,
       Keyword.DO,
       Keyword.FINAL,
       Keyword.FOR,
@@ -434,8 +448,13 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
       offset = completion.length;
     }
     request.addSuggestion(new CompletionSuggestion(
-        CompletionSuggestionKind.KEYWORD, relevance, completion, offset, 0,
-        false, false));
+        CompletionSuggestionKind.KEYWORD,
+        relevance,
+        completion,
+        offset,
+        0,
+        false,
+        false));
   }
 
   void _addSuggestions(List<Keyword> keywords,
@@ -463,4 +482,20 @@ class _KeywordVisitor extends GeneralizingAstVisitor {
       node = parent;
     }
   }
+
+  bool _inDoLoop(AstNode node) =>
+      node.getAncestor((p) => p is DoStatement) != null;
+
+  bool _inForLoop(AstNode node) =>
+      node.getAncestor((p) => p is ForStatement || p is ForEachStatement) !=
+          null;
+
+  bool _inLoop(AstNode node) =>
+      _inDoLoop(node) || _inForLoop(node) || _inWhileLoop(node);
+
+  bool _inSwitch(AstNode node) =>
+      node.getAncestor((p) => p is SwitchStatement) != null;
+
+  bool _inWhileLoop(AstNode node) =>
+      node.getAncestor((p) => p is WhileStatement) != null;
 }