8000 Recursive conditional types by ahejlsberg · Pull Request #40002 · microsoft/TypeScript · GitHub
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Recursive conditional types #40002

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Merged
merged 12 commits into from
Aug 16, 2020
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ahejlsberg committed Aug 13, 2020
commit fed0e8c71b505a73ae536d68a60d61edf6445a47
Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ tests/cases/compiler/recursiveConditionalTypes.ts(89,9): error TS2345: Argument
T;

type MyPromise<T> = {
then<U>(f: ((value: T) => U | MyPromise<U>) | null | undefined): MyPromise<U>;
then<U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined): MyPromise<U>;
}

type InfinitePromise<T> = Promise<InfinitePromise<T>>;
Expand Down Expand Up @@ -129,7 +129,7 @@ tests/cases/compiler/recursiveConditionalTypes.ts(89,9): error TS2345: Argument

declare let z: Box2<Box2<string>>;

foo(z); // string
foo(z); // unknown, but ideally would be string (requires unique recursion ID for each type reference)

// Intersect tuple element types

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ type Awaited<T> =
T;

type MyPromise<T> = {
then<U>(f: ((value: T) => U | MyPromise<U>) | null | undefined): MyPromise<U>;
then<U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined): MyPromise<U>;
}

type InfinitePromise<T> = Promise<InfinitePromise<T>>;
Expand Down Expand Up @@ -64,7 +64,7 @@ declare function foo<T>(x: Box1<Box1<T>>): T;

declare let z: Box2<Box2<string>>;

foo(z); // string
foo(z); // unknown, but ideally would be string (requires unique recursion ID for each type reference)

// Intersect tuple element types

Expand Down Expand Up @@ -105,7 +105,7 @@ function f22(tn, tm) {
tm = tn;
}
f23(['a', 'b', 'c']); // string
foo(z); // string
foo(z); // unknown, but ideally would be string (requires unique recursion ID for each type reference)
function f20(x, y) {
x = y;
y = x;
Expand All @@ -119,7 +119,7 @@ function f21(x, y) {
//// [recursiveConditionalTypes.d.ts]
declare type Awaited<T> = T extends null | undefined ? T : T extends PromiseLike<infer U> ? Awaited<U> : T;
declare type MyPromise<T> = {
then<U>(f: ((value: T) => U | MyPromise<U>) | null | undefined): MyPromise<U>;
then<U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined): MyPromise<U>;
};
declare type InfinitePromise<T> = Promise<InfinitePromise<T>>;
declare type P0 = Awaited<Promise<string | Promise<MyPromise<number> | null> | undefined>>;
Expand Down
6 changes: 3 additions & 3 deletions tests/baselines/reference/recursiveConditionalTypes.symbols
Original file line number Diff line number Diff line change
Expand Up @@ -23,14 +23,14 @@ type MyPromise<T> = {
>MyPromise : Symbol(MyPromise, Decl(recursiveConditionalTypes.ts, 5, 6))
>T : Symbol(T, Decl(recursiveConditionalTypes.ts, 7, 15))

then<U>(f: ((value: T) => U | MyPromise<U>) | null | undefined): MyPromise<U>;
then<U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined): MyPromise<U>;
>then : Symbol(then, Decl(recursiveConditionalTypes.ts, 7, 21))
>U : Symbol(U, Decl(recursiveConditionalTypes.ts, 8, 9))
>f : Symbol(f, Decl(recursiveConditionalTypes.ts, 8, 12))
>value : Symbol(value, Decl(recursiveConditionalTypes.ts, 8, 17))
>T : Symbol(T, Decl(recursiveConditionalTypes.ts, 7, 15))
>U : Symbol(U, Decl(recursiveConditionalTypes.ts, 8, 9))
>MyPromise : Symbol(MyPromise, Decl(recursiveConditionalTypes.ts, 5, 6))
>PromiseLike : Symbol(PromiseLike, Decl(lib.es5.d.ts, --, --))
>U : Symbol(U, Decl(recursiveConditionalTypes.ts, 8, 9))
>MyPromise : Symbol(MyPromise, Decl(recursiveConditionalTypes.ts, 5, 6))
>U : Symbol(U, Decl(recursiveConditionalTypes.ts, 8, 9))
Expand Down Expand Up @@ -243,7 +243,7 @@ declare let z: Box2<Box2<string>>;
>Box2 : Symbol(Box2, Decl(recursiveConditionalTypes.ts, 58, 28))
>Box2 : Symbol(Box2, Decl(recursiveConditionalTypes.ts, 58, 28))

foo(z); // string
foo(z); // unknown, but ideally would be string (requires unique recursion ID for each type reference)
>foo : Symbol(foo, Decl(recursiveConditionalTypes.ts, 59, 28))
>z : Symbol(z, Decl(recursiveConditionalTypes.ts, 63, 11))

Expand Down
10 changes: 5 additions & 5 deletions tests/baselines/reference/recursiveConditionalTypes.types
Original file line number Diff line number Diff line change
Expand Up @@ -13,9 +13,9 @@ type Awaited<T> =
type MyPromise<T> = {
>MyPromise : MyPromise<T>

then<U>(f: ((value: T) => U | MyPromise<U>) | null | undefined): MyPromise<U>;
>then : <U>(f: ((value: T) => U | MyPromise<U>) | null | undefined) => MyPromise<U>
>f : ((value: T) => U | MyPromise<U>) | null | undefined
then<U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined): MyPromise<U>;
>then : <U>(f: ((value: T) => U | PromiseLike<U>) | null | undefined) => MyPromise<U>
>f : ((value: T) =& 6FE8 gt; U | PromiseLike<U>) | null | undefined
>value : T
>null : null
}
Expand Down Expand Up @@ -152,8 +152,8 @@ declare function foo<T>(x: Box1<Box1<T>>): T;
declare let z: Box2<Box2<string>>;
>z : Box2<Box2<string>>

foo(z); // string
>foo(z) : string
foo(z); // unknown, but ideally would be string (requires unique recursion ID for each type reference)
>foo(z) : unknown
>foo : <T>(x: Box1<Box1<T>>) => T
>z : Box2<Box2<string>>

Expand Down
0