diff --git a/src/compiler/resolutionCache.ts b/src/compiler/resolutionCache.ts
index 31fa0222151..3ce4eb934a5 100644
--- a/src/compiler/resolutionCache.ts
+++ b/src/compiler/resolutionCache.ts
@@ -687,7 +687,7 @@ namespace ts {
                         (filesWithInvalidatedResolutions || (filesWithInvalidatedResolutions = createMap<true>())).set(containingFilePath, true);
 
                         // When its a file with inferred types resolution, invalidate type reference directive resolution
-                        if (containingFilePath.endsWith(inferredTypesContainingFile)) {
+                        if (endsWith(containingFilePath, inferredTypesContainingFile)) {
                             resolutionHost.onChangedAutomaticTypeDirectiveNames();
                         }
                     }
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index bf76051b6ad..7377e2a4c66 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -2444,7 +2444,7 @@ namespace ts {
         return String.fromCharCode(codeUnit1, codeUnit2);
     }
 
-    const utf16EncodeAsStringWorker: (codePoint: number) => string = (String as any).fromCodePoint ? codePoint => String.fromCodePoint(codePoint) : utf16EncodeAsStringFallback;
+    const utf16EncodeAsStringWorker: (codePoint: number) => string = (String as any).fromCodePoint ? codePoint => (String as any).fromCodePoint(codePoint) : utf16EncodeAsStringFallback;
 
     /* @internal */
     export function utf16EncodeAsString(codePoint: number) {
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index 52ca65d0b95..519fead62c7 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -1004,14 +1004,14 @@ namespace ts {
         writeFloatBE(value: number, offset: number): number;
         writeDoubleLE(value: number, offset: number): number;
         writeDoubleBE(value: number, offset: number): number;
-        readBigUInt64BE(offset?: number): bigint;
-        readBigUInt64LE(offset?: number): bigint;
-        readBigInt64BE(offset?: number): bigint;
-        readBigInt64LE(offset?: number): bigint;
-        writeBigInt64BE(value: bigint, offset?: number): number;
-        writeBigInt64LE(value: bigint, offset?: number): number;
-        writeBigUInt64BE(value: bigint, offset?: number): number;
-        writeBigUInt64LE(value: bigint, offset?: number): number;
+        readBigUInt64BE?(offset?: number): bigint;
+        readBigUInt64LE?(offset?: number): bigint;
+        readBigInt64BE?(offset?: number): bigint;
+        readBigInt64LE?(offset?: number): bigint;
+        writeBigInt64BE?(value: bigint, offset?: number): number;
+        writeBigInt64LE?(value: bigint, offset?: number): number;
+        writeBigUInt64BE?(value: bigint, offset?: number): number;
+        writeBigUInt64LE?(value: bigint, offset?: number): number;
         fill(value: string | Uint8Array | number, offset?: number, end?: number, encoding?: BufferEncoding): this;
         indexOf(value: string | number | Uint8Array, byteOffset?: number, encoding?: BufferEncoding): number;
         lastIndexOf(value: string | number | Uint8Array, byteOffset?: number, encoding?: BufferEncoding): number;