fix

Author: Phoebe Szmucer

src/services/stringCompletions.ts

@@ -650,11 +650,11 @@ function getBaseDirectoriesFromRootDirs(rootDirs: string[], basePath: string, sc
     rootDirs = rootDirs.map(rootDirectory => ensureTrailingDirectorySeparator(normalizePath(isRootedDiskPath(rootDirectory) ? rootDirectory : combinePaths(basePath, rootDirectory))));
 
     // Determine the path to the directory containing the script relative to the root directory it is contained within
-    const relativeDirectory = firstDefined(rootDirs, rootDirectory => containsPath(rootDirectory, scriptDirectory, basePath, ignoreCase) ? scriptDirectory.substr(rootDirectory.length) : undefined)!; // TODO: GH#18217
+    const relativeDirectory = firstDefined(rootDirs, rootDirectory => containsPath(rootDirectory, scriptDirectory, basePath, ignoreCase) ? scriptDirectory.substr(rootDirectory.length) : undefined);
 
     // Now find a path for each potential directory that is to be merged with the one containing the script
     return deduplicate<string>(
-        [...rootDirs.map(rootDirectory => combinePaths(rootDirectory, relativeDirectory)), scriptDirectory],
+        [...rootDirs.map(rootDirectory => combinePaths(rootDirectory, relativeDirectory)), scriptDirectory].map(baseDir => removeTrailingDirectorySeparator(baseDir)),
         equateStringsCaseSensitive,
         compareStringsCaseSensitive,
     );