Fix symbolCanBeReferencedAtTypeLocation for namespace that exports itself

Author: Andy Hanson

src/services/completions.ts

@@ -1128,23 +1128,13 @@ namespace ts.Completions {
             return false;
         }
 
-        function symbolCanBeReferencedAtTypeLocation(symbol: Symbol): boolean {
-            symbol = symbol.exportSymbol || symbol;
-
-            // This is an alias, follow what it aliases
-            symbol = skipAlias(symbol, typeChecker);
-
-            if (symbol.flags & SymbolFlags.Type) {
-                return true;
-            }
-
-            if (symbol.flags & SymbolFlags.Module) {
-                const exportedSymbols = typeChecker.getExportsOfModule(symbol);
-                // If the exported symbols contains type,
-                // symbol can be referenced at locations where type is allowed
-                return exportedSymbols.some(symbolCanBeReferencedAtTypeLocation);
-            }
-            return false;
+        /** True if symbol is a type or a module containing at least one type. */
+        function symbolCanBeReferencedAtTypeLocation(symbol: Symbol, seenModules = createMap<true>()): boolean {
+            const sym = skipAlias(symbol.exportSymbol || symbol, typeChecker);
+            return !!(sym.flags & SymbolFlags.Type) ||
+                !!(sym.flags & SymbolFlags.Module) &&
+                addToSeen(seenModules, getSymbolId(sym)) &&
+                typeChecker.getExportsOfModule(sym).some(e => symbolCanBeReferencedAtTypeLocation(e, seenModules));
         }
 
         function getSymbolsFromOtherSourceFileExports(symbols: Symbol[], tokenText: string, target: ScriptTarget): void {

tests/cases/fourslash/completionsRecursiveNamespace.ts

@@ -0,0 +1,9 @@
+/// <reference path='fourslash.ts'/>
+
+////declare namespace N {
+////    export import M = N;
+////}
+////type T = N./**/
+
+// Previously this would crash in `symbolCanBeReferencedAtTypeLocation` due to the namespace exporting itself.
+verify.completions({ marker: "", exact: undefined });