Special case known good names for use-before-def

src/Analysis/Engine/Impl/Analyzer/ExpressionEvaluator.cs

@@ -150,7 +150,18 @@ public IAnalysisSet LookupAnalysisSetByName(Node node, string name, bool addRef
                         res = refs.Types;
                     } else {
                         // ... warn the user
-                        warn = !(node is ConstantExpression); // Don't warn when None.
+                        // "atom" in Python grammar.
+                        switch (name) {
+                            case "None":
+                            case "False":
+                            case "True":
+                            case "...":
+                            case string _ when node is ConstantExpression:
+                                break;
+                            default:
+                                warn = true;
+                                break;
+                        }
                     }
                 }
             }

src/Analysis/Engine/Test/LanguageServerTests.cs

@@ -363,18 +363,15 @@ public async Task DiagnosticsSettingChange() {
             }
         }
 
-        [TestMethod, Priority(0)]
-        public async Task TypeHintNoneDiagnostic() {
+        [DataRow("def f(b: None) -> None:\n    b: None")]
+        [DataRow("from typing import Generator\ndef fun() -> Generator[int, None, None]:\n    yield from range(10)")]
+        [DataTestMethod, Priority(0)]
+        public async Task TypeHintNoneDiagnostic(string code) {
             if (this is LanguageServerTests_V2) {
                 // No type hints in Python 2.
                 return;
             }
 
-            var code = @"
-def f(b: None) -> None:
-    b: None
-";
-
             var diags = new Dictionary<Uri, PublishDiagnosticsEventArgs>();
             using (var s = await CreateServer((Uri)null, null, diags)) {
                 var u = await s.OpenDefaultDocumentAndGetUriAsync(code);