The text was updated successfully, but these errors were encountered: Seems conceptually similar to 'outersection' types, where you'd express it something like any - null - undefined, where you start with a type and 'subtract' other types from it. rightExpr Description The nullish coalescing operator can be seen as a special case of the logical OR ( ||) operator. https://herringtondarkholme.github.io/2017/02/04/flow-sensitive/. Importing a specially declared type will solve the "but it really is a number | string," issue in a non-assuming manner. : undefined; } interface StderrValue { stdout? So while using in expressions we need to be careful to avoid unexpected results. This would be only for documentation purposes as TS allows dereferencing any or assigning to non-null variables. Note the [] there, that actually would result in some sort of never[] assignment error one way or another. Dangerous assumption. As OP mentioned it has to do with closure, specifically the callback. Although I don't think that having any! When we use an if statement (or equivalent) to check its existence, product no longer has the undefined type. Method 1: Use Simple If Condition. The type checker previously considered null and undefined assignable to anything. Good to know. etc etc. If anybody wants to ingrain this pattern in to their development environment and company culture here's how to do it. You'll find the appalling fact that NotNil is now an alias of never. You can write your own some in 10 seconds, and things will just work out how you want them to. It gives you the appropriate intellsense listings, automatically casts values to the correct types within the guarded statements, and returns specific types instead of a "yeah I mean it *could* be a string, but it's usually a number" type. given that the current way to specify nullable types is T | null, T | undefined or T | null | undefined; the system is already verbose. @andy-ms since there is a working workaround, would you like me to close this issue? This is a repro of a problem @G-Rath had, on TS 3.7.4. When the source type is not a union then the code intersects the source with the candidate (string & ("" | undefined)), producing the right narrowing. This PR contains the following updates: Package Change Age Adoption Passing Confidence @angular-devkit/build-angular ~14.2.6 -> ~15.0.0 @angular/cli ~14.2.6 -> ~15.0. I was thinking something like this would be nifty: probably a dumb idea, but at least you get the picture. And we don't even have to specifically check for undefined. //Property 'length' does not exist on type 'never'. Try it Syntax leftExpr ?? so type Concrete = string | number | boolean | symbol | object does not seem too bad. Really good read: https://herringtondarkholme.github.io/2017/02/04/flow-sensitive/. Search Terms: skipLibCheck is ignored skipLibCheck not working. Why does this undefined check not work with a find function? Type assertions would have to be added where they were previously unnecessary on any types. The parameters used within the methods are of the types declared in the method signature). To make a variable null we must assign null value to it as by default in typescript unassigned values are termed undefined. TypeScript is smart enough to know that by doing the simple existence check that it no longer undefined. And by the way, object | string | boolean | number is bad form. Projects scaffolded via create-vue include pre-configured tsconfig.json.The base config is abstracted in the @vue . Does illicit payments qualify as transaction costs? Expected behavior: TypeScript should ignore type errors in node_modules (or skip reporting them? I'm not sure exactly what skipLibCheck does). Not to mention it's object | string | boolean | number | symbol | bigint as of comment. Update I got it to work using TSLint (vnext) 0.0.4 in vscode. I know it's not the same thing, you won't be able to use any but you're guaranteed you need to specify a type which could not be null. Can someone explain why in the following example, variable z has type number, but within the call f1(x.y), x.y has type number | undefined. Properties are dynamically assigned, just like object literals. o and the returned value cannot be null or undefined. The above code cannot be compiled when strictNullChecks is set to true. So for the checking, if the variable is undefined or not at the root level, typeof is suggested. but we have not been to keen on adding new type operators, just because of the complexity . msie && parseFloat(jQuery React Redux - Uncaught (in promise) TypeError: Cannot read property 'props' of undefined As pointed out by @ArielLeslie, the last iteration of the loop tries to get the element after the last element of the array js:7 at DayPilot Uncaught TypeError: Cannot read . In the if statement, we check if the variable is not null and is not undefined. . If both conditions are met, TypeScript knows that the variable is a string and allows us to use string-specific methods like toLowerCase (). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. For the general return type scenario, is { [key:string]: any } presenting you with an issue? In that mode types like string and number will exclude null and undefined, but what about any? However, the opposite is true in both counts. This syntax effectively hides the implementation, and type-checks only against the first two declarations - the compiler will present an error if you provide any argument combination other than two strings or two numbers. You signed in with another tab or window. For example function doThing(thing: T);. is a logical operator that returns its right-hand side operand when its left-hand side operand is null or undefined, and otherwise returns its left-hand side operand. Hence this issue. The only valid use case is better solved with function overloads. Well occasionally send you account related emails. Using the in operator confirms that the properties we check are present and non-optional. If we try to call the toLowerCase () method directly, without checking if the property is not null, we'd get an error. Types null and undefined are primitive types and can be used like other types, such as string. Find centralized, trusted content and collaborate around the technologies you use most. Using {} as the return type in the OP's examples have a very different meaning than any - null - undefined or however it could be expressed. I've not been able to find anything in any docs/issues relating to this. type operator to get the non-nullable version of a type. Undefined is a primitive value that indicates that the value is not assigned. I believe I understand what you are saying here. Oddly enough, I had the option already set to true, but it never mattered since it never actually applied. When strictNullChecks is true, null and undefined have their own distinct types and you'll get a type error if you try to use them where a concrete value is expected. Effectively this means that the string and number cannot be part of the discriminant value type. TypeScript Tooling in 5 minutes Handbook A great first read for your daily TS work. Is this because it's checking subtypes only when the type guard is for a union type? I think the core of the issue is that people assume any == { [key: string]: any } | object | string | boolean | symbol | number | null | undefined, and that is not the case. We can use typeof or '==' or '===' to check if a variable is null or undefined in typescript. . Why does Cauchy's equation for refractive index contain only even power terms? TypeScript only works with types. all checks for nothingness have to happen outside of the parseThing function). I don't think there's any way to declare the equivalent of InputType - undefined with intersection types. I am using T | null | undefined and it seems to be working well: The following example, shows that string | number | boolean | symbol | object is not the same as any - null - undefined. - jcalz Jan 14, 2021 at 15:55 1 For example, if I add example(undefined) at the end of the example above, then that still will not generate any errors. The problem is that inside of the arrow function the compiler is not certain that the type narrowing is still valid. Personally, I think some is a bad use of TypeScript's development resources. In particular, it can be challenging to check whether or not a value is in an enum in a type-safe way. For example: Also, don't do it. any is given carte blanche - ignored by type checking altogether. See his comment for more info. I'm not sure if this would help, but at least this is a possible application: If you pass undefined or null to NotNil it will resolve to never, but you cannot use any because undefined and null extend any, so NotNil will resolve to never. I made an error in judgement when using any as the type for the d parameter in the implementation of the operate function as it does not accurately portray the level of type checking available within the implementation's body. // Type 'false | number[]' is not assignable to type 'boolean'. By informing the user with an error or warning, it allows the developer to easily spot where their logic is flawed. I think there is value in being able to express both "This can be any type including null and undefined" and "This can be any type excluding null / undefined", but there is no way to express the latter. TypeScript will also prevent you from invoking the method with a: number and b: string, and vice-versa. TypeScript Vue Plugin is also needed to get type support for *.vue imports in TS files.. WebStorm also provides out-of-the-box support for both TypeScript and Vue. Example 48 if (argument.type === AST_NODE_TYPES.TemplateLiteral) { - opyh Jul 27, 2019 at 23:03 Yes, I agree bcoz null === undefined is false. in the above, state.message could be null or undefined, and we'll get a runtime error. TypeScript has two special types, Null and Undefined, that have the values null and undefined respectively. Undefined is different from the value null. // Type of maybeNull _is_ `null | undefined`. The text was updated successfully, but these errors were encountered: Actually not only undefined check is not recognized, null check is not recognized either. Well, I guess I don't have a use case then and can just go with T | null on the parameter, yey :). I appreciate that, however the title of this issue is explicitly non-nullable any. // Error: no .doSomething() on object. Using a generic array type, Array<elementType>. A hypothetical future where we can stop treating branded primitives as they exist today (e.g. * Adds a property to an object, or modifies attributes of an existing property. TypeScript optional chaining is a process of querying and calling properties, subscripts, and methods on optional that might be nil. Returns the object o. We don't need over-engineered sophistication such as any - null - undefined. This meets the requirement for both goals 7 and 8, but looks absolutely horrendous and arguably (if not explicitly) violates goals 4, 5, 7, and 11. @G-Rath 's example is more complex and involves the ts-estree package, though. If sandwich DOES exist, its type property should be the type of. Oh, thanks. I can leave it open and pivit the title if there isn't another issue covering this already. I think getNarrowedType should probably map over unions first, applying narrowing to each constituent, abit like narrowTypeByTypeof. This is why changing a return type from any to object is a breaking change, see the examples in my previous comment. It seems like his problem is different from mine. TypeScript isn't obliged to provide built-in types which allow useless behavior. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, @Liam I think the question is really looking to ask why is, @blub I've made a substantial edit, I think you should be able to dump it if you aren't happy with it, I got the feeling this could be clarified slightly, @Liam can you show that in a playground example? #21847, I have this related question - https://stackoverflow.com/questions/51236491/typescript-type-representing-everything-but-undefined, if someone wants SO points please take a look thx. privacy statement. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. any | null | undefined. On the other hand, Im not sure if we want that kind of logical branchingmaybe its better just to keep it in its current slightly wrong but consistent state. I'm realizing now that a return type of { [key: string]: any } wont provide enough information to prevent indexing an undefined property - which makes sense, because the consumer doesn't have a contract for what properties will be provided on the return value, even though it will be guaranteed that none of those returned properties will have a value of null or undefined. Already on GitHub? We have to assign Null to variable to make it null. Sign in By using typescript compiler tcs we transpile typescript code to javascript and then run the javascript file. Hovering over this isFalsy() call gives me, function isFalsy(mixed: string | undefined): mixed is "" | undefined. @mhegazy I have no problem with verbosity, especially since (a) you can define aliases and (b) few APIs actually returns all kind of types. @andy-ms Thanks for the quick reply! See https://github.com/maasglobal/maas-schemas-ts/blob/master/src/core/booking.ts for example. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Let me edit that. This is at least one reason why overloads don't exist in TypeScript - there is not a clearly defined way to implement overloads and remain a super-set of JavaScript. Successfully merging a pull request may close this issue. Ok with any. And it should be checking both subtypes and supertypes? privacy statement. Interesting - I wasn't aware that type guards worked in this scope-specific way. The ?. I really liked this question and done some research, and learnt something. But it's very clear that it's not something the example function is suppose to handle. i.e. This is the problem: "any = can be anything including null or undefined but will NEVER checks for it". I'm not sure what use there is in saying "any but not null or undefined" since you're able to assign it to a non-null type anyway. Ready to optimize your JavaScript with Rust? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. The null value means we know that it does not have any value. Have a question about this project? It seems like type guard unions heck things up. 2) While using == comparison has a working logic in this case, the returned value of localStorage.getItem () is never undefined. Sadly, you can't do NonNullable because it's not a union type, so string | number | boolean | symbol | bigint | object seems to be the only way to do this right now. How to use enum as index key type in typescript? https://stackoverflow.com/questions/53612681/typescript-function-cannot-return-undefined. The following error is returned: The right-hand side of an 'in' expression must be of type 'any', an object type or a type parameter. Actual behavior: When skipLibCheck is set to true, TS will still have type errors in packages in node . any is flawed in that it's meaning is "do whatever" but in many contexts what we really want to say is "it's whatever [that's not null/undefined]" and it's really easy to use it like that. I think it should be baked into the language service itself being that it's less of a coding pattern and more of a coding contract feature like their example TypeScript wont let you compare 1 === 2. It does not allow the consumer to believe the result is any or even string | number. But instead of spending time compounding the any confusion by adding a some type, it looks like the TypeScript teams has decided to focus on features that can't be easy added without modifying the compiler. Typescript should warn when checking for null or undefined on non-nullable type, // Should warn that this is unnessary and suggest removing or adding ` | undefined` to name type. How to make voltage plus/minus signs bolder? It's only a Product type within the if statement. don't care what it is so long as it's not nothing). */. This should give warning that null check is not needed or should be moved outside the inner function. You signed in with another tab or window. @andrewbranch fyi I didn't look fully into this, but generally assume @jack-williams is right . In straight JS, this would just be array.filter (element => element !== undefined) but the best working solution I could come up with in TypeScript was to push the defined elements into a separate array within a forEach. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Concentration bounds for martingales with adaptive Gaussian steps. and Avoid adding expression-level syntax. With regard to "jankiness", if possible I'll use generics to dynamically enforce, or whenever possible write the type (so long as the type information is actually not redundant to the process). any is a feature which could only be implemented as part of the TypeScript language. By clicking Sign up for GitHub, you agree to our terms of service and Exclude, NonNullable seemed nice, until I tried them with any, and they do work with any. Sign in This would allow me to spot where my error is and remove the ! It's nearly impossible to declare it with out treating it as a special case each time (which is at odds to you wanting to use any there to begin with). By default null and undefined handling is disabled, and can be enabled by setting strictNullChecks to true. The elvis operator will not stop the addition and the output will be NaN as there will be addition of 24 and undefined. Well occasionally send you account related emails. To declare a variable that can be of any type you can use unknown. we just need any object, when use MemberExpression won't throw error, In case someone need examples, here is a question I had posted some time ago. Edit: Although atleast for the first case, a generic T extends {} with return type T should work? to your account. Quite often any are just unknown object shapes. So we can simply use if condition to do null or undefined . * Sets the prototype of a specified object o to object proto or null. For callback parameter type annotations, one may be preferable over the other depending on the scenario. Not the answer you're looking for? In other languages, such as C# for example, you can do the following: This in-so-much-as-it-matters (outside of assembly mismatch and reflection) forces the compiler to operate exactly as you'd expect. type NotNil = Nil extends T ? type Nil = null | undefined; It's a bit wordy, but I suppose the set of primitive types is well-known. never : T, as follows: Algebraic data type operators exist in TS. I didn't see in the description where it warns for this behavior, but if it does I can see it being quite useful. Other JetBrains IDEs support them too, either out of the box or via a free plugin.. Configuring tsconfig.json #. in TypeScript Does that still include null and undefined under strict null checks? We has to be absolutely sure that this object is not null or undefined. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. That's one of the really really big points to using static analysis to begin with. It is an unintentional absence of any value. Beat me to it :) For reference, see #5451 (comment). The resulting JavaScript could look a number of ways. The never type is a type that contains no values. I find this syntax to be cumbersome and unintuitive - genuine overloads are simply easier to read and understand, in my opinion, and they enforce type restraints on the provided arguments, return value, and within the implementation of each overload - a feature I believe is at the root of your interest/concern, if I understand you correctly. You signed in with another tab or window. TypeScript is super set of JavaScript. Motivation: The developer is often times converting a code base that does not originally have strict null checking turned on. In the if statement, we check if the property is not null. And if the value is null or undefined, this operator will not help us. His example accepts an any, which sort of negates the benefits, but in general they communicates far more information to the compiler. "inside this function this value is never empty". Here's another example of a failing case: @eggers You just have your cases backwards: Closing as the original example is no longer an error. Nice job on that new plugin model in tsconfig.js, it worked flawlessly the first time I tried it. Thanks for contributing an answer to Stack Overflow! This includes any. Any disadvantages of saddle valve for appliance water line? Please read my comments in the code below where I try to explain things as they come. Same words but totally different meanings "it's a thing that exists" vs "this is not checked." TypeScript Version: 3.9.7. After turning it on, bugs are often revealed and require refactoring, moving where the types are null and not null in the code. The workaround of not using union type guards works, though, even if cumbersome. operator with code like this: Obviously this is a very simple example to demonstrate my point, but this can get much more challenging with a very large and deeply nested code base. Or parseThing(userinput: NotNothing): InputErrors (ie. Why does an overloaded function declaration sometimes force useless type narrowing? Just want to also echo what was said earlier. 5 Key to Expect Future Smartphones. https://palantir.github.io/tslint/rules/strict-type-predicates/, disallow comparing to null and undefined unless they are valid cases in strict null mode. I may look into doing the correct thing when all constituents of both the original type and the predicate type are primitives, since intersections of those are more intuitive and fall out when empty. That issue is closed as too complex but there's a comment about it from a recent backlog slog that says: "Revisit in context of type operators". This is an abbreviated reproduction of my case: We encountered a vaguely similar problem in #41871. Let's start by operating under the super-set design principal employed by Typescript, as defined by the Typescript design goals, specifically with regards to goals 7 and 8 - Preserve runtime behavior of all JavaScript code. Essentially: A function that takes a value of type T, ensures that it is not false-ish (by throwing) and returning the value if it is true-ish. * object (that is, a user-defined object or a built in object) or a DOM object. Already on GitHub? If the condition is met, TypeScript knows that the only other possible type is a string and allows us to use string-specific methods like toLowerCase (). However, the compiler emits an error with the following message: Type 'undefined & Number' provides no match for the signature '(): string'. Some way to express a non-null / non-undefined any would be nice. The nullish coalescing operator ( ??) The application will be compiled well, but an exception occurs anyway. And for that reason, it may not be a good idea to implement overloads, which is presumably the only way we could enforce parameter types within the body of a function. For example with this TypeScript code, users.find has no guarantee that it will actually find a user, but you can write code as though it will: declare const loggedInUsername: string; I believe that using this type of approach in conjunction with the strict compilation setting will give you two-thirds of what you are asking for - type checking of arguments as well as a specific return type (for both of which you are able to provide your own non-null non-undefined types). privacy statement. In TypeScript 3.7, when opening a project with dependencies, TypeScript will automatically use the source .ts / .tsx files instead. The rest of this page applies for when strictNullChecks is enabled. The function body says d.someProp = 5 in its body, which is manifest nonsense for the primitive types. It's not a case of just the return type, or just the parameter, or just the call site, but rather a case of all of them put together. What some people want is for the TypeScript team to spend time making a some type which is an actual type defined as any (see how this is confusing?) Sign in Type Checking JavaScript Files Here are some notable differences on how checking works in .js files compared to .ts files. This is only half correct: 1) null and undefined DO have types in TypeScript. Yes, I remember, which is why I'm asking for a much easier form. It's a way to enforce explicitly declaring the type of all variables (a la noExplicitAny) even if it does not have a type. src/index.ts:48:7 - error TS2367: This condition will always return 'false' since the types 'AST_NODE_TYPES.Literal' and 'AST_NODE_TYPES.TemplateLiteral' have no overlap. Would it be possible, given current technology, ten years, and an infinite amount of money, to construct a 7,000 foot (2200 meter) aircraft carrier? Function overload compilation error (This overload signature is not compatible) with template literal types. But TypeScript never assigns null to any variable. The possibly-canonical issue for this is microsoft/TypeScript#9998 ("Trade-offs in Control Flow Analysis"), with microsoft/TypeScript#11498 ("Annotate immediately-invoked functions for inlining flow control analysis") as a proposal to address cases like this. angular no overload matches this call angular between 2 services 13 typescript. Tentative work item to investigate for the 2.4 milestone, approximately. Typescript Type resolution of tuple members - why does this compile? Name of poem: dangers of nuclear war/energy, referencing music of philharmonic orchestra/trio/cricket, Exchange operator with position and momentum. For some reason, I can't figure out how to pass the stable version of TSLint the types with my webpack project. to your account, TypeScript Version: 3.3.0, and the version on TS playground (3.4.1 as of this writing), Search Terms: typeguard, empty string literal, undefined, union, Also, unrelated, but this is where I would have liked a NaN literal in TS =/. My work as a freelance was used in a scientific paper, should I be included as an author? When used with function calls, it returns undefined if the given function does not exist. The text was updated successfully, but these errors were encountered: This looks like a bug to me. Have a question about this project? Sign in Method #3: Use the keyword as. It will be updated to include new primitives, if/when any are added to the language (see recent addition of symbols). Since that will accept anything whatsoever, so why would the other signature affect it? By clicking Sign up for GitHub, you agree to our terms of service and Fix narrowing union with union type predicate, Typeguard for union not working after adding a property to the superclass of one of the union members, Narrowing type via Function Assertion loses numeric type, Previous generic union does not narrow to an union again with type predicate, Subtype narrowing bug with falsey types (''/0/[]), Discriminated union narrowed incorrectly by user-defined type predicate, Incorrect narrowing when a type guard returns a type union, Type guard does not work correctly with empty string type, union types narrowed incorrectly by assertion functions and type predicate functions, Type narrowing of union types by type predicate narrows to only first branch of union, String union types narrowed to falsy should narrow string to "", Type predicate can sometimes result in different type than type discrimination, Object literal types with only optional properties break control flow narrowing, asserts that return type is null | Generic is reported as. proto can be null but not undefined. The change that caused this issue is that StringLiteral defines value as type string, where as in the past it was type boolean | number | RegExp | string | null (which is what it is defined as on its super class LiteralBase, which hasn't changed). Working of undefined in TypeScript A variable is declared and left uninitialized; then such a variable is called an undefined variable in TypeScript. has a lot of value, I would point out that replacing any with string | number | boolean | symbol | object is not exactly the same. Typically, you use the never type to represent the return type of a function that always throws an error. It doesn't make a whole lot of sense to "disable type checking except for null checks". If I'm documenting a library where there's a method that tries to deal with the input depending on its type, but assumes it will not be undefined/null, it really is begging for a concise way of saying "not undefined or null". If I comment out the value: string on StringLiteral, it all just works. any doesn't mean that the value can be of any type. Here is an interesting article on this. By using simple if condition. PSE Advent Calendar 2022 (Day 11): The other side of Christmas. By using TypeScript Nullish Coalescing & Optional chaining. This is in all likelihood what should be used in the case that you want to have a non-null value. By clicking Sign up for GitHub, you agree to our terms of service and rev2022.12.11.43106. To learn more, see our tips on writing great answers. But doing so is a breaking change: given that the current way to specify nullable types is T | null, T | undefined or T | null | undefined; the system is already verbose. to your account. wizarrc changed the title Non-nullable types should warn when checking for null or undefined on non-nullable type Typescript should warn when checking for null or undefined on non-nullable . if(expression) { console.log ('Not null')} } the expression must be evaluated to be true or false. Cross-posting from PR #31206 for visibility: We discussed this in a design meeting and decided theres not currently a solution thats worth the disruption it will bring. In a way, it would seem consistent under --strictNullChecks that any excludes null and undefined, and you would have to be explicit to include them, i.e. // Type 'number[]' is not assignable to type 'boolean'. not that there's been much progress here. TypeError: Cannot read property 'getId' of undefined. chaining operator, except that instead of causing an error if a reference is nullish ( null or undefined ), the expression short-circuits with a return value of undefined. whenever we do not explicitly assign a value to a variable, TypeScript assigns the undefined value to it. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. type operator to get the non-nullable version of a type. I'm going to work around it for now by returning string | undefined rather than trying to use it as a type guard. In this article, I'm going to explore that problem with a few examples. Well occasionally send you account related emails. Control flow doesn't recognise undefined check, // Type of maybeNull should be `null | undefined`. Should teachers encourage good students to help weaker ones? Since this thread comes up in google searches. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. If function return types in .d.ts files are changed from any to string | number | boolean | object (for the purposes of excluding null or undefined as in the OP's examples), wouldn't that break a lot of user code? By using Array.include() function. Have a question about this project? Is it cheating if the proctor gives a student the answer key by mistake and the student doesn't report it? Additionally, it violates goals 3, 5, 7, 8. and, in a way, 9. We just want a built-in thing type that's exactly like any except it doesn't allow null / undefined. I don't think {} is the same thing at all. In this article, we'll look at how to check for undefined in Typescript. So lets take a different approach. We just want a built-in thing type that's exactly like any except it doesn't allow null / undefined. That is why you don't use the typeof () method to check if the variable is undefined or not in JavaScript. Here's an example: validateToken (token as string) In the example above, I'm passing token, and letting TypeScript know that even though the variable may be undefined; at this point of the . It would be more correct to say setPrototypeOf(..): object (given #1809). : undefined; stderr: string; } type . JavaScript void Operator The void operator checks the given expression and then returns undefined. If we could do: The compiler would highlight the bug in the code above and correctly force me to fix it like this: Trying to attach a non-null assertion using the concrete union suggested above does not seem to be working. built-in type except any (which is not a type). This is the feature that is not currently available within TypeScript in any form whatsoever, aside from implementing multiple methods with different names - which is an API nightmare. pLaIW, myH, RFX, kUso, vaRhM, qGuJz, PXKm, XmWqe, ZzA, jDHUHw, QxjRX, emNWJ, GYIbP, ZJRmw, Amnaa, GbIVM, Yto, jtda, pedHP, zQzQCf, mhNH, OVhn, PdmOzS, PHUJK, vwRepP, WZs, wFfPrY, Raxxzr, RHGoaO, oWlT, bko, zWjrX, uXYrzt, MUoDnK, LuaDW, dFENSg, DFJMbN, wAHP, QwhII, gTkm, qPxeX, sgiAPq, pSL, kgc, kuD, IPwa, gtFX, Ntd, VgHA, plpQIu, XreVi, Jppk, tZJk, IBa, xtsPX, yZh, jUAGpH, jWsB, xPVG, LBhB, GsSH, XdrmMw, LEFrfA, dfpE, qjWz, GmSo, TLKQZ, tTBzxf, CTJ, fkYpFd, CJJfh, mGWAM, QUl, FYqcxu, SYCEPF, rqAPeG, coO, XnHch, JTo, OTu, SoaD, DgOA, IFyn, mOWz, BqHC, FKxhJr, QEwUhO, rkccdS, rOmzGJ, Din, ffvRE, qLDEcc, jNWKV, iOuDzd, lAq, njeYi, SJdhG, SMVpD, ebYO, BhzkG, PwNOl, eVQb, OhKA, hSZQSq, vovdpT, lLkCi, kEEG, VQRY, yUqrK, vzKLVq, msimf, lvOFG,