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Fix isGenericReducibleType to allow HKT technique to function again #54112

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merged 4 commits into from
May 20, 2023
Merged

Fix isGenericReducibleType to allow HKT technique to function again #54112

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33aeffb
Improve type inference to allow HKT technique function again
ahejlsberg May 3, 2023
dd88229
Add regression test
ahejlsberg May 3, 2023
f104b53
Revert changes and instead fix isGenericObjectType to be more conserv…
ahejlsberg May 4, 2023
64a864b
Accept new baselines
ahejlsberg May 4, 2023
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11 changes: 10 additions & 1 deletion src/compiler/checker.ts
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Expand Up @@ -17685,7 +17685,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// eagerly using the constraint type of 'this' at the given location.
if (isGenericIndexType(indexType) || (accessNode && accessNode.kind !== SyntaxKind.IndexedAccessType ?
isGenericTupleType(objectType) && !indexTypeLessThan(indexType, objectType.target.fixedLength) :
isGenericObjectType(objectType) && !(isTupleType(objectType) && indexTypeLessThan(indexType, objectType.target.fixedLength)) || isGenericReducibleType(objectType))) {
isGenericObjectType(objectType) && !(isTupleType(objectType) && indexTypeLessThan(indexType, objectType.target.fixedLength)) || !(accessFlags & AccessFlags.ResolveReducibleTypes) && isGenericReducibleType(objectType))) {
if (objectType.flags & TypeFlags.AnyOrUnknown) {
return objectType;
}
Expand Down Expand Up @@ -24511,6 +24511,15 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
}
}
// The following is a targeted fix to allow higher-kinded types to be emulated using the technique in #53970.
// Specifically, when an indexed access type was deferred because it has a reducible object type, here we force
// resolution of the type and then infer to the result.
if (target.flags & TypeFlags.IndexedAccess && isGenericReducibleType((target as IndexedAccessType).objectType)) {
const instantiated = getIndexedAccessType((target as IndexedAccessType).objectType, (target as IndexedAccessType).indexType, AccessFlags.ResolveReducibleTypes);
if (instantiated && instantiated !== target) {
inferFromTypes(source, instantiated);
}
}
}
if (getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(target) & ObjectFlags.Reference && (
(source as TypeReference).target === (target as TypeReference).target || isArrayType(source) && isArrayType(target)) &&
Expand Down
19 changes: 10 additions & 9 deletions src/compiler/types.ts
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Expand Up @@ -6593,15 +6593,16 @@ export interface TypeParameter extends InstantiableType {
export const enum AccessFlags {
None = 0,
IncludeUndefined = 1 << 0,
NoIndexSignatures = 1 << 1,
Writing = 1 << 2,
CacheSymbol = 1 << 3,
NoTupleBoundsCheck = 1 << 4,
ExpressionPosition = 1 << 5,
ReportDeprecated = 1 << 6,
SuppressNoImplicitAnyError = 1 << 7,
Contextual = 1 << 8,
Persistent = IncludeUndefined,
ResolveReducibleTypes = 1 << 1,
NoIndexSignatures = 1 << 2,
Writing = 1 << 3,
CacheSymbol = 1 << 4,
NoTupleBoundsCheck = 1 << 5,
ExpressionPosition = 1 << 6,
ReportDeprecated = 1 << 7,
SuppressNoImplicitAnyError = 1 << 8,
Contextual = 1 << 9,
Persistent = IncludeUndefined | ResolveReducibleTypes,
}

// Indexed access types (TypeFlags.IndexedAccess)
Expand Down
100 changes: 100 additions & 0 deletions tests/baselines/reference/inferenceAndHKTs.symbols
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@@ -0,0 +1,100 @@
=== tests/cases/compiler/inferenceAndHKTs.ts ===
// Repro from #53970

export interface TypeLambda {
>TypeLambda : Symbol(TypeLambda, Decl(inferenceAndHKTs.ts, 0, 0))

readonly A: unknown;
>A : Symbol(TypeLambda.A, Decl(inferenceAndHKTs.ts, 2, 29))
}

export interface TypeClass<F extends TypeLambda> {
>TypeClass : Symbol(TypeClass, Decl(inferenceAndHKTs.ts, 4, 1))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 6, 27))
>TypeLambda : Symbol(TypeLambda, Decl(inferenceAndHKTs.ts, 0, 0))

readonly _F: F;
>_F : Symbol(TypeClass._F, Decl(inferenceAndHKTs.ts, 6, 50))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 6, 27))
}

export type Apply<F extends TypeLambda, A> = F extends { readonly type: unknown }
>Apply : Symbol(Apply, Decl(inferenceAndHKTs.ts, 8, 1))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 10, 18))
>TypeLambda : Symbol(TypeLambda, Decl(inferenceAndHKTs.ts, 0, 0))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 10, 39))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 10, 18))
>type : Symbol(type, Decl(inferenceAndHKTs.ts, 10, 56))

? (F & { readonly A: A })['type']
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 10, 18))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 11, 12))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 10, 39))

: { readonly F: F, readonly A: A };
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 12, 7))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 10, 18))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 12, 22))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 10, 39))

export interface T<A> {
>T : Symbol(T, Decl(inferenceAndHKTs.ts, 12, 39))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 14, 19))

value: A;
>value : Symbol(T.value, Decl(inferenceAndHKTs.ts, 14, 23))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 14, 19))
}

export interface TTypeLambda extends TypeLambda {
>TTypeLambda : Symbol(TTypeLambda, Decl(inferenceAndHKTs.ts, 16, 1))
>TypeLambda : Symbol(TypeLambda, Decl(inferenceAndHKTs.ts, 0, 0))

readonly type: T<this["A"]>;
>type : Symbol(TTypeLambda.type, Decl(inferenceAndHKTs.ts, 18, 49))
>T : Symbol(T, Decl(inferenceAndHKTs.ts, 12, 39))
}

export declare const map: <F extends TypeLambda>(F: TypeClass<F>) => <A, B>(a: Apply<F, A>, f: (a: A) => B) => Apply<F, B>;
>map : Symbol(map, Decl(inferenceAndHKTs.ts, 22, 20))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 22, 27), Decl(inferenceAndHKTs.ts, 22, 49))
>TypeLambda : Symbol(TypeLambda, Decl(inferenceAndHKTs.ts, 0, 0))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 22, 27), Decl(inferenceAndHKTs.ts, 22, 49))
>TypeClass : Symbol(TypeClass, Decl(inferenceAndHKTs.ts, 4, 1))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 22, 27), Decl(inferenceAndHKTs.ts, 22, 49))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 22, 70))
>B : Symbol(B, Decl(inferenceAndHKTs.ts, 22, 72))
>a : Symbol(a, Decl(inferenceAndHKTs.ts, 22, 76))
>Apply : Symbol(Apply, Decl(inferenceAndHKTs.ts, 8, 1))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 22, 27), Decl(inferenceAndHKTs.ts, 22, 49))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 22, 70))
>f : Symbol(f, Decl(inferenceAndHKTs.ts, 22, 91))
>a : Symbol(a, Decl(inferenceAndHKTs.ts, 22, 96))
>A : Symbol(A, Decl(inferenceAndHKTs.ts, 22, 70))
>B : Symbol(B, Decl(inferenceAndHKTs.ts, 22, 72))
>Apply : Symbol(Apply, Decl(inferenceAndHKTs.ts, 8, 1))
>F : Symbol(F, Decl(inferenceAndHKTs.ts, 22, 27), Decl(inferenceAndHKTs.ts, 22, 49))
>B : Symbol(B, Decl(inferenceAndHKTs.ts, 22, 72))

declare const typeClass: TypeClass<TTypeLambda>;
>typeClass : Symbol(typeClass, Decl(inferenceAndHKTs.ts, 24, 13))
>TypeClass : Symbol(TypeClass, Decl(inferenceAndHKTs.ts, 4, 1))
>TTypeLambda : Symbol(TTypeLambda, Decl(inferenceAndHKTs.ts, 16, 1))

declare const a: T<number>;
>a : Symbol(a, Decl(inferenceAndHKTs.ts, 26, 13))
>T : Symbol(T, Decl(inferenceAndHKTs.ts, 12, 39))

const x1 = map(typeClass);
>x1 : Symbol(x1, Decl(inferenceAndHKTs.ts, 28, 5))
>map : Symbol(map, Decl(inferenceAndHKTs.ts, 22, 20))
>typeClass : Symbol(typeClass, Decl(inferenceAndHKTs.ts, 24, 13))

const x2 = map(typeClass)(a, (_) => _); // T<number>
>x2 : Symbol(x2, Decl(inferenceAndHKTs.ts, 29, 5))
>map : Symbol(map, Decl(inferenceAndHKTs.ts, 22, 20))
>typeClass : Symbol(typeClass, Decl(inferenceAndHKTs.ts, 24, 13))
>a : Symbol(a, Decl(inferenceAndHKTs.ts, 26, 13))
>_ : Symbol(_, Decl(inferenceAndHKTs.ts, 29, 30))
>_ : Symbol(_, Decl(inferenceAndHKTs.ts, 29, 30))

64 changes: 64 additions & 0 deletions tests/baselines/reference/inferenceAndHKTs.types
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@@ -0,0 +1,64 @@
=== tests/cases/compiler/inferenceAndHKTs.ts ===
// Repro from #53970

export interface TypeLambda {
readonly A: unknown;
>A : unknown
}

export interface TypeClass<F extends TypeLambda> {
readonly _F: F;
>_F : F
}

export type Apply<F extends TypeLambda, A> = F extends { readonly type: unknown }
>Apply : Apply<F, A>
>type : unknown

? (F & { readonly A: A })['type']
>A : A

: { readonly F: F, readonly A: A };
>F : F
>A : A

export interface T<A> {
value: A;
>value : A
}

export interface TTypeLambda extends TypeLambda {
readonly type: T<this["A"]>;
>type : T<this["A"]>
}

export declare const map: <F extends TypeLambda>(F: TypeClass<F>) => <A, B>(a: Apply<F, A>, f: (a: A) => B) => Apply<F, B>;
>map : <F extends TypeLambda>(F: TypeClass<F>) => <A, B>(a: Apply<F, A>, f: (a: A) => B) => Apply<F, B>
>F : TypeClass<F>
>a : Apply<F, A>
>f : (a: A) => B
>a : A

declare const typeClass: TypeClass<TTypeLambda>;
>typeClass : TypeClass<TTypeLambda>

declare const a: T<number>;
>a : T<number>

const x1 = map(typeClass);
>x1 : <A, B>(a: (TTypeLambda & { readonly A: A; })["type"], f: (a: A) => B) => (TTypeLambda & { readonly A: B; })["type"]
>map(typeClass) : <A, B>(a: (TTypeLambda & { readonly A: A; })["type"], f: (a: A) => B) => (TTypeLambda & { readonly A: B; })["type"]
>map : <F extends TypeLambda>(F: TypeClass<F>) => <A, B>(a: Apply<F, A>, f: (a: A) => B) => Apply<F, B>
>typeClass : TypeClass<TTypeLambda>

const x2 = map(typeClass)(a, (_) => _); // T<number>
>x2 : T<number>
>map(typeClass)(a, (_) => _) : T<number>
>map(typeClass) : <A, B>(a: (TTypeLambda & { readonly A: A; })["type"], f: (a: A) => B) => (TTypeLambda & { readonly A: B; })["type"]
>map : <F extends TypeLambda>(F: TypeClass<F>) => <A, B>(a: Apply<F, A>, f: (a: A) => B) => Apply<F, B>
>typeClass : TypeClass<TTypeLambda>
>a : T<number>
>(_) => _ : (_: number) => number
>_ : number
>_ : number

33 changes: 33 additions & 0 deletions tests/cases/compiler/inferenceAndHKTs.ts
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@@ -0,0 +1,33 @@
// @strict: true
// @noEmit: true

// Repro from #53970

export interface TypeLambda {
readonly A: unknown;
}

export interface TypeClass<F extends TypeLambda> {
readonly _F: F;
}

export type Apply<F extends TypeLambda, A> = F extends { readonly type: unknown }
? (F & { readonly A: A })['type']
: { readonly F: F, readonly A: A };

export interface T<A> {
value: A;
}

export interface TTypeLambda extends TypeLambda {
readonly type: T<this["A"]>;
}

export declare const map: <F extends TypeLambda>(F: TypeClass<F>) => <A, B>(a: Apply<F, A>, f: (a: A) => B) => Apply<F, B>;

declare const typeClass: TypeClass<TTypeLambda>;

declare const a: T<number>;

const x1 = map(typeClass);
const x2 = map(typeClass)(a, (_) => _); // T<number>