Prevent crash on code fixes on default keyword (microsoft#48028)

Author: jakebailey

src/services/codefixes/importFixes.ts

@@ -847,9 +847,10 @@ namespace ts.codefix {
         const checker = program.getTypeChecker();
         const compilerOptions = program.getCompilerOptions();
         const symbolName = getSymbolName(sourceFile, checker, symbolToken, compilerOptions);
-        // "default" is a keyword and not a legal identifier for the import, so we don't expect it here
-        Debug.assert(symbolName !== InternalSymbolName.Default, "'default' isn't a legal identifier and couldn't occur here");
-
+        // "default" is a keyword and not a legal identifier for the import, but appears as an identifier.
+        if (symbolName === InternalSymbolName.Default) {
+            return undefined;
+        }
         const isValidTypeOnlyUseSite = isValidTypeOnlyAliasUseSite(symbolToken);
         const useRequire = shouldUseRequire(sourceFile, program);
         const exportInfo = getExportInfos(symbolName, isJSXTagName(symbolToken), getMeaningFromLocation(symbolToken), cancellationToken, sourceFile, program, useAutoImportProvider, host, preferences);

tests/cases/fourslash/addAllMissingImportsNoCrash2.ts

@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: file1.ts
+//// export { /**/default };
+
+goTo.marker();
+
+verify.not.codeFixAllAvailable("fixMissingImport");