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Fix conditional type resolution #29338

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Merged
merged 3 commits into from
Jan 10, 2019
Merged

Fix conditional type resolution #29338

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70148a4
Improve logic that determines when to resolve conditional types
ahejlsberg Jan 10, 2019
9fda701
Add regression tests
ahejlsberg Jan 10, 2019
0c1c97e
Accept new baselines
ahejlsberg Jan 10, 2019
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134 changes: 68 additions & 66 deletions src/compiler/checker.ts
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4 changes: 3 additions & 1 deletion src/compiler/types.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3916,7 +3916,9 @@ namespace ts {
aliasTypeArguments?: ReadonlyArray<Type>; // Alias type arguments (if any)
/* @internal */ aliasTypeArgumentsContainsMarker?: boolean; // Alias type arguments (if any)
/* @internal */
wildcardInstantiation?: Type; // Instantiation with type parameters mapped to wildcard type
permissiveInstantiation?: Type; // Instantiation with type parameters mapped to wildcard type
/* @internal */
restrictiveInstantiation?: Type; // Instantiation with type parameters mapped to unconstrained form
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Should permissiveInstantiations and restrictiveInstantiations have pointers back to the original type, this way when we attempt to get them, if we already have one of them we can avoid bothering instantiating a new type (and often creating a new type identity)?

/* @internal */
immediateBaseConstraint?: Type; // Immediate base constraint cache
}
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8 changes: 8 additions & 0 deletions tests/baselines/reference/conditionalTypes1.errors.txt
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Expand Up @@ -471,4 +471,12 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(288,43): error TS

var a = {o: 1, b: 2, c: [{a: 1, c: '213'}]}
assign(a, {o: 2, c: {0: {a: 2, c: '213123'}}})

// Repros from #23843

type Weird1 = (<U extends boolean>(a: U) => never) extends
(<U extends true>(a: U) => never) ? never : never;

type Weird2 = (<U extends boolean>(a: U) => U) extends
(<U extends true>(a: U) => infer T) ? T : never;

10 changes: 10 additions & 0 deletions tests/baselines/reference/conditionalTypes1.js
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Expand Up @@ -351,6 +351,14 @@ declare function assign<T>(o: T, a: RecursivePartial<T>): void;

var a = {o: 1, b: 2, c: [{a: 1, c: '213'}]}
assign(a, {o: 2, c: {0: {a: 2, c: '213123'}}})

// Repros from #23843

type Weird1 = (<U extends boolean>(a: U) => never) extends
(<U extends true>(a: U) => never) ? never : never;

type Weird2 = (<U extends boolean>(a: U) => U) extends
(<U extends true>(a: U) => infer T) ? T : never;


//// [conditionalTypes1.js]
Expand Down Expand Up @@ -715,3 +723,5 @@ declare var a: {
c: string;
}[];
};
declare type Weird1 = (<U extends boolean>(a: U) => never) extends (<U extends true>(a: U) => never) ? never : never;
declare type Weird2 = (<U extends boolean>(a: U) => U) extends (<U extends true>(a: U) => infer T) ? T : never;
27 changes: 27 additions & 0 deletions tests/baselines/reference/conditionalTypes1.symbols
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Expand Up @@ -1371,3 +1371,30 @@ assign(a, {o: 2, c: {0: {a: 2, c: '213123'}}})
>a : Symbol(a, Decl(conditionalTypes1.ts, 351, 25))
>c : Symbol(c, Decl(conditionalTypes1.ts, 351, 30))

// Repros from #23843

type Weird1 = (<U extends boolean>(a: U) => never) extends
>Weird1 : Symbol(Weird1, Decl(conditionalTypes1.ts, 351, 46))
>U : Symbol(U, Decl(conditionalTypes1.ts, 355, 16))
>a : Symbol(a, Decl(conditionalTypes1.ts, 355, 35))
>U : Symbol(U, Decl(conditionalTypes1.ts, 355, 16))

(<U extends true>(a: U) => never) ? never : never;
>U : Symbol(U, Decl(conditionalTypes1.ts, 356, 6))
>a : Symbol(a, Decl(conditionalTypes1.ts, 356, 22))
>U : Symbol(U, Decl(conditionalTypes1.ts, 356, 6))

type Weird2 = (<U extends boolean>(a: U) => U) extends
>Weird2 : Symbol(Weird2, Decl(conditionalTypes1.ts, 356, 54))
>U : Symbol(U, Decl(conditionalTypes1.ts, 358, 16))
>a : Symbol(a, Decl(conditionalTypes1.ts, 358, 35))
>U : Symbol(U, Decl(conditionalTypes1.ts, 358, 16))
>U : Symbol(U, Decl(conditionalTypes1.ts, 358, 16))

(<U extends true>(a: U) => infer T) ? T : never;
>U : Symbol(U, Decl(conditionalTypes1.ts, 359, 6))
>a : Symbol(a, Decl(conditionalTypes1.ts, 359, 22))
>U : Symbol(U, Decl(conditionalTypes1.ts, 359, 6))
>T : Symbol(T, Decl(conditionalTypes1.ts, 359, 36))
>T : Symbol(T, Decl(conditionalTypes1.ts, 359, 36))

18 changes: 18 additions & 0 deletions tests/baselines/reference/conditionalTypes1.types
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Expand Up @@ -1054,3 +1054,21 @@ assign(a, {o: 2, c: {0: {a: 2, c: '213123'}}})
>c : string
>'213123' : "213123"

// Repros from #23843

type Weird1 = (<U extends boolean>(a: U) => never) extends
>Weird1 : never
>a : U

(<U extends true>(a: U) => never) ? never : never;
>true : true
>a : U

type Weird2 = (<U extends boolean>(a: U) => U) extends
>Weird2 : boolean
>a : U

(<U extends true>(a: U) => infer T) ? T : never;
>true : true
>a : U

8 changes: 8 additions & 0 deletions tests/cases/conformance/types/conditional/conditionalTypes1.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -353,3 +353,11 @@ declare function assign<T>(o: T, a: RecursivePartial<T>): void;

var a = {o: 1, b: 2, c: [{a: 1, c: '213'}]}
assign(a, {o: 2, c: {0: {a: 2, c: '213123'}}})

// Repros from #23843

type Weird1 = (<U extends boolean>(a: U) => never) extends
(<U extends true>(a: U) => never) ? never : never;

type Weird2 = (<U extends boolean>(a: U) => U) extends
(<U extends true>(a: U) => infer T) ? T : never;