Workaround compile issues caused by PR

Author: AlexMarkUSDS

src/compiler/moduleSpecifiers.ts

@@ -996,7 +996,7 @@ function tryGetModuleNameFromRootDirs(rootDirs: readonly string[], moduleFileNam
 }
 
 function tryGetModuleNameAsNodeModule({ path, isRedirect }: ModulePath, { getCanonicalFileName, canonicalSourceDirectory }: Info, importingSourceFile: SourceFile, host: ModuleSpecifierResolutionHost, options: CompilerOptions, userPreferences: UserPreferences, packageNameOnly?: boolean, overrideMode?: ResolutionMode): string | undefined {
-    if (!host.fileExists || !host.readFile) {
+    if (host.fileExists === undefined || !host.readFile) {
         return undefined;
     }
     const parts: NodeModulePathParts = getNodeModulePathParts(path)!;
@@ -1145,7 +1145,7 @@ function tryGetModuleNameAsNodeModule({ path, isRedirect }: ModulePath, { getCan
 }
 
 function tryGetAnyFileFromPath(host: ModuleSpecifierResolutionHost, path: string) {
-    if (!host.fileExists) return;
+    if (host.fileExists === undefined) return;
     // We check all js, `node` and `json` extensions in addition to TS, since node module resolution would also choose those over the directory
     const extensions = flatten(getSupportedExtensions({ allowJs: true }, [{ extension: "node", isMixedContent: false }, { extension: "json", isMixedContent: false, scriptKind: ScriptKind.JSON }]));
     for (const e of extensions) {

src/compiler/sys.ts

@@ -131,7 +131,7 @@ let pollingChunkSize = createPollingIntervalBasedLevels(defaultChunkLevels);
 export let unchangedPollThresholds = createPollingIntervalBasedLevels(defaultChunkLevels);
 
 function setCustomPollingValues(system: System) {
-    if (!system.getEnvironmentVariable) {
+    if (system.getEnvironmentVariable === undefined) {
         return;
     }
     const pollingIntervalChanged = setCustomLevels("TSC_WATCH_POLLINGINTERVAL", PollingInterval);