Remove nonNullUnknownType (#57665)

Author: jakebailey

src/compiler/checker.ts

@@ -1968,7 +1968,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     var nonInferrableAnyType = createIntrinsicType(TypeFlags.Any, "any", ObjectFlags.ContainsWideningType, "non-inferrable");
     var intrinsicMarkerType = createIntrinsicType(TypeFlags.Any, "intrinsic");
     var unknownType = createIntrinsicType(TypeFlags.Unknown, "unknown");
-    var nonNullUnknownType = createIntrinsicType(TypeFlags.Unknown, "unknown", /*objectFlags*/ undefined, "non-null");
     var undefinedType = createIntrinsicType(TypeFlags.Undefined, "undefined");
     var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(TypeFlags.Undefined, "undefined", ObjectFlags.ContainsWideningType, "widening");
     var missingType = createIntrinsicType(TypeFlags.Undefined, "undefined", /*objectFlags*/ undefined, "missing");
@@ -17293,7 +17292,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (includes & TypeFlags.AnyOrUnknown) {
                 return includes & TypeFlags.Any ?
                     includes & TypeFlags.IncludesWildcard ? wildcardType : anyType :
-                    includes & TypeFlags.Null || containsType(typeSet, unknownType) ? unknownType : nonNullUnknownType;
+                    unknownType;
             }
             if (includes & TypeFlags.Undefined) {
                 // If type set contains both undefinedType and missingType, remove missingType
@@ -27738,8 +27737,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         if (resultType === unreachableNeverType || reference.parent && reference.parent.kind === SyntaxKind.NonNullExpression && !(resultType.flags & TypeFlags.Never) && getTypeWithFacts(resultType, TypeFacts.NEUndefinedOrNull).flags & TypeFlags.Never) {
             return declaredType;
         }
-        // The non-null unknown type should never escape control flow analysis.
-        return resultType === nonNullUnknownType ? unknownType : resultType;
+        return resultType;
 
         function getOrSetCacheKey() {
             if (isKeySet) {