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Improve contextual typing by generic rest parameters #30114

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Feb 28, 2019
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Improve contextual typing by generic rest parameters #30114

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451f653
Improve contextual typing by generic rest parameter
ahejlsberg Feb 19, 2019
f19191b
Add tests
ahejlsberg Feb 19, 2019
d0cb047
Accept new baselines
ahejlsberg Feb 19, 2019
0716b87
Merge branch 'master' into contextualGenericRestParameter
ahejlsberg Feb 26, 2019
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17 changes: 14 additions & 3 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -10678,9 +10678,9 @@ namespace ts {
return !!(<InferenceContext>mapper).typeParameters;
}

function cloneTypeMapper(mapper: TypeMapper): TypeMapper {
function cloneTypeMapper(mapper: TypeMapper, extraFlags: InferenceFlags = 0): TypeMapper {
return mapper && isInferenceContext(mapper) ?
createInferenceContext(mapper.typeParameters, mapper.signature, mapper.flags | InferenceFlags.NoDefault, mapper.compareTypes, mapper.inferences) :
createInferenceContext(mapper.typeParameters, mapper.signature, mapper.flags | extraFlags, mapper.compareTypes, mapper.inferences) :
mapper;
}

Expand Down Expand Up @@ -20018,7 +20018,7 @@ namespace ts {
// We clone the contextual mapper to avoid disturbing a resolution in progress for an
// outer call expression. Effectively we just want a snapshot of whatever has been
// inferred for any outer call expression so far.
const instantiatedType = instantiateType(contextualType, cloneTypeMapper(getContextualMapper(node)));
const instantiatedType = instantiateType(contextualType, cloneTypeMapper(getContextualMapper(node), InferenceFlags.NoDefault));
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The cloneTypeMapper call used to create the returnType mapper inside call resolution doesn't pass InferenceFlags.NoDefault with this change. Intentional?

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Yes, it's intentional. We only want the InferenceFlags.NoDefault behavior here (because we're transposing inferences from the outer call mapper and don't want an absence of inferences in the outer mapper to turn into what appears to be a concrete inference of the default).

// If the contextual type is a generic function type with a single call signature, we
// instantiate the type with its own type parameters and type arguments. This ensures that
// the type parameters are not erased to type any during type inference such that they can
Expand Down Expand Up @@ -21686,6 +21686,17 @@ namespace ts {
}
}
}
const restType = getEffectiveRestType(context);
if (restType && restType.flags & TypeFlags.TypeParameter) {
// The contextual signature has a generic rest parameter. We first instantiate the contextual
// signature (without fixing type parameters) and assign types to contextually typed parameters.
const instantiatedContext = instantiateSignature(context, cloneTypeMapper(mapper));
assignContextualParameterTypes(signature, instantiatedContext);
// We then infer from a tuple type representing the parameters that correspond to the contextual
// rest parameter.
const restPos = getParameterCount(context) - 1;
inferTypes((<InferenceContext>mapper).inferences, getRestTypeAtPosition(signature, restPos), restType);
}
}

function assignContextualParameterTypes(signature: Signature, context: Signature) {
Expand Down
15 changes: 15 additions & 0 deletions tests/baselines/reference/restTuplesFromContextualTypes.errors.txt
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Expand Up @@ -68,6 +68,21 @@ tests/cases/conformance/types/rest/restTuplesFromContextualTypes.ts(56,7): error
!!! error TS2345: Property '0' is missing in type 'any[]' but required in type '[T[0], ...T[number][]]'.
}

declare function f5<T extends any[], U>(f: (...args: T) => U): (...args: T) => U;

let g0 = f5(() => "hello");
let g1 = f5((x, y) => 42);
let g2 = f5((x: number, y) => 42);
let g3 = f5((x: number, y: number) => x + y);
let g4 = f5((...args) => true);

declare function pipe<A extends any[], B, C>(f: (...args: A) => B, g: (x: B) => C): (...args: A) => C;

let g5 = pipe(() => true, b => 42);
let g6 = pipe(x => "hello", s => s.length);
let g7 = pipe((x, y) => 42, x => "" + x);
let g8 = pipe((x: number, y: string) => 42, x => "" + x);

// Repro from #25288

declare var tuple: [number, string];
Expand Down
41 changes: 41 additions & 0 deletions tests/baselines/reference/restTuplesFromContextualTypes.js
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Expand Up @@ -57,6 +57,21 @@ function f4<T extends any[]>(t: T) {
f((a, b, ...x) => {});
}

declare function f5<T extends any[], U>(f: (...args: T) => U): (...args: T) => U;

let g0 = f5(() => "hello");
let g1 = f5((x, y) => 42);
let g2 = f5((x: number, y) => 42);
let g3 = f5((x: number, y: number) => x + y);
let g4 = f5((...args) => true);

declare function pipe<A extends any[], B, C>(f: (...args: A) => B, g: (x: B) => C): (...args: A) => C;

let g5 = pipe(() => true, b => 42);
let g6 = pipe(x => "hello", s => s.length);
let g7 = pipe((x, y) => 42, x => "" + x);
let g8 = pipe((x: number, y: string) => 42, x => "" + x);

// Repro from #25288

declare var tuple: [number, string];
Expand Down Expand Up @@ -275,6 +290,21 @@ function f4(t) {
}
});
}
var g0 = f5(function () { return "hello"; });
var g1 = f5(function (x, y) { return 42; });
var g2 = f5(function (x, y) { return 42; });
var g3 = f5(function (x, y) { return x + y; });
var g4 = f5(function () {
var args = [];
for (var _i = 0; _i < arguments.length; _i++) {
args[_i] = arguments[_i];
}
return true;
});
var g5 = pipe(function () { return true; }, function (b) { return 42; });
var g6 = pipe(function (x) { return "hello"; }, function (s) { return s.length; });
var g7 = pipe(function (x, y) { return 42; }, function (x) { return "" + x; });
var g8 = pipe(function (x, y) { return 42; }, function (x) { return "" + x; });
(function foo(a, b) { }.apply(void 0, tuple));
(function foo() {
var rest = [];
Expand Down Expand Up @@ -309,6 +339,17 @@ declare function f2(cb: (...args: typeof t2) => void): void;
declare const t3: [boolean, ...string[]];
declare function f3(cb: (x: number, ...args: typeof t3) => void): void;
declare function f4<T extends any[]>(t: T): void;
declare function f5<T extends any[], U>(f: (...args: T) => U): (...args: T) => U;
declare let g0: () => string;
declare let g1: (x: any, y: any) => number;
declare let g2: (x: number, y: any) => number;
declare let g3: (x: number, y: number) => number;
declare let g4: (...args: any[]) => boolean;
declare function pipe<A extends any[], B, C>(f: (...args: A) => B, g: (x: B) => C): (...args: A) => C;
declare let g5: () => number;
declare let g6: (x: any) => number;
declare let g7: (x: any, y: any) => string;
declare let g8: (x: number, y: string) => string;
declare var tuple: [number, string];
declare function take(cb: (a: number, b: string) => void): void;
declare type ArgsUnion = [number, string] | [number, Error];
Expand Down
146 changes: 117 additions & 29 deletions tests/baselines/reference/restTuplesFromContextualTypes.symbols
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Expand Up @@ -238,67 +238,155 @@ function f4<T extends any[]>(t: T) {
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 55, 12))
}

declare function f5<T extends any[], U>(f: (...args: T) => U): (...args: T) => U;
>f5 : Symbol(f5, Decl(restTuplesFromContextualTypes.ts, 56, 1))
>T : Symbol(T, Decl(restTuplesFromContextualTypes.ts, 58, 20))
>U : Symbol(U, Decl(restTuplesFromContextualTypes.ts, 58, 36))
>f : Symbol(f, Decl(restTuplesFromContextualTypes.ts, 58, 40))
>args : Symbol(args, Decl(restTuplesFromContextualTypes.ts, 58, 44))
>T : Symbol(T, Decl(restTuplesFromContextualTypes.ts, 58, 20))
>U : Symbol(U, Decl(restTuplesFromContextualTypes.ts, 58, 36))
>args : Symbol(args, Decl(restTuplesFromContextualTypes.ts, 58, 64))
>T : Symbol(T, Decl(restTuplesFromContextualTypes.ts, 58, 20))
>U : Symbol(U, Decl(restTuplesFromContextualTypes.ts, 58, 36))

let g0 = f5(() => "hello");
>g0 : Symbol(g0, Decl(restTuplesFromContextualTypes.ts, 60, 3))
>f5 : Symbol(f5, Decl(restTuplesFromContextualTypes.ts, 56, 1))

let g1 = f5((x, y) => 42);
>g1 : Symbol(g1, Decl(restTuplesFromContextualTypes.ts, 61, 3))
>f5 : Symbol(f5, Decl(restTuplesFromContextualTypes.ts, 56, 1))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 61, 13))
>y : Symbol(y, Decl(restTuplesFromContextualTypes.ts, 61, 15))

let g2 = f5((x: number, y) => 42);
>g2 : Symbol(g2, Decl(restTuplesFromContextualTypes.ts, 62, 3))
>f5 : Symbol(f5, Decl(restTuplesFromContextualTypes.ts, 56, 1))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 62, 13))
>y : Symbol(y, Decl(restTuplesFromContextualTypes.ts, 62, 23))

let g3 = f5((x: number, y: number) => x + y);
>g3 : Symbol(g3, Decl(restTuplesFromContextualTypes.ts, 63, 3))
>f5 : Symbol(f5, Decl(restTuplesFromContextualTypes.ts, 56, 1))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 63, 13))
>y : Symbol(y, Decl(restTuplesFromContextualTypes.ts, 63, 23))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 63, 13))
>y : Symbol(y, Decl(restTuplesFromContextualTypes.ts, 63, 23))

let g4 = f5((...args) => true);
>g4 : Symbol(g4, Decl(restTuplesFromContextualTypes.ts, 64, 3))
>f5 : Symbol(f5, Decl(restTuplesFromContextualTypes.ts, 56, 1))
>args : Symbol(args, Decl(restTuplesFromContextualTypes.ts, 64, 13))

declare function pipe<A extends any[], B, C>(f: (...args: A) => B, g: (x: B) => C): (...args: A) => C;
>pipe : Symbol(pipe, Decl(restTuplesFromContextualTypes.ts, 64, 31))
>A : Symbol(A, Decl(restTuplesFromContextualTypes.ts, 66, 22))
>B : Symbol(B, Decl(restTuplesFromContextualTypes.ts, 66, 38))
>C : Symbol(C, Decl(restTuplesFromContextualTypes.ts, 66, 41))
>f : Symbol(f, Decl(restTuplesFromContextualTypes.ts, 66, 45))
>args : Symbol(args, Decl(restTuplesFromContextualTypes.ts, 66, 49))
>A : Symbol(A, Decl(restTuplesFromContextualTypes.ts, 66, 22))
>B : Symbol(B, Decl(restTuplesFromContextualTypes.ts, 66, 38))
>g : Symbol(g, Decl(restTuplesFromContextualTypes.ts, 66, 66))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 66, 71))
>B : Symbol(B, Decl(restTuplesFromContextualTypes.ts, 66, 38))
>C : Symbol(C, Decl(restTuplesFromContextualTypes.ts, 66, 41))
>args : Symbol(args, Decl(restTuplesFromContextualTypes.ts, 66, 85))
>A : Symbol(A, Decl(restTuplesFromContextualTypes.ts, 66, 22))
>C : Symbol(C, Decl(restTuplesFromContextualTypes.ts, 66, 41))

let g5 = pipe(() => true, b => 42);
>g5 : Symbol(g5, Decl(restTuplesFromContextualTypes.ts, 68, 3))
>pipe : Symbol(pipe, Decl(restTuplesFromContextualTypes.ts, 64, 31))
>b : Symbol(b, Decl(restTuplesFromContextualTypes.ts, 68, 25))

let g6 = pipe(x => "hello", s => s.length);
>g6 : Symbol(g6, Decl(restTuplesFromContextualTypes.ts, 69, 3))
>pipe : Symbol(pipe, Decl(restTuplesFromContextualTypes.ts, 64, 31))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 69, 14))
>s : Symbol(s, Decl(restTuplesFromContextualTypes.ts, 69, 27))
>s.length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
>s : Symbol(s, Decl(restTuplesFromContextualTypes.ts, 69, 27))
>length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))

let g7 = pipe((x, y) => 42, x => "" + x);
>g7 : Symbol(g7, Decl(restTuplesFromContextualTypes.ts, 70, 3))
>pipe : Symbol(pipe, Decl(restTuplesFromContextualTypes.ts, 64, 31))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 70, 15))
>y : Symbol(y, Decl(restTuplesFromContextualTypes.ts, 70, 17))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 70, 27))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 70, 27))

let g8 = pipe((x: number, y: string) => 42, x => "" + x);
>g8 : Symbol(g8, Decl(restTuplesFromContextualTypes.ts, 71, 3))
>pipe : Symbol(pipe, Decl(restTuplesFromContextualTypes.ts, 64, 31))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 71, 15))
>y : Symbol(y, Decl(restTuplesFromContextualTypes.ts, 71, 25))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 71, 43))
>x : Symbol(x, Decl(restTuplesFromContextualTypes.ts, 71, 43))

// Repro from #25288

declare var tuple: [number, string];
>tuple : Symbol(tuple, Decl(restTuplesFromContextualTypes.ts, 60, 11))
>tuple : Symbol(tuple, Decl(restTuplesFromContextualTypes.ts, 75, 11))

(function foo(a, b){}(...tuple));
>foo : Symbol(foo, Decl(restTuplesFromContextualTypes.ts, 61, 1))
>a : Symbol(a, Decl(restTuplesFromContextualTypes.ts, 61, 14))
>b : Symbol(b, Decl(restTuplesFromContextualTypes.ts, 61, 16))
>tuple : Symbol(tuple, Decl(restTuplesFromContextualTypes.ts, 60, 11))
>foo : Symbol(foo, Decl(restTuplesFromContextualTypes.ts, 76, 1))
>a : Symbol(a, Decl(restTuplesFromContextualTypes.ts, 76, 14))
>b : Symbol(b, Decl(restTuplesFromContextualTypes.ts, 76, 16))
>tuple : Symbol(tuple, Decl(restTuplesFromContextualTypes.ts, 75, 11))

// Repro from #25289

declare function take(cb: (a: number, b: string) => void): void;
>take : Symbol(take, Decl(restTuplesFromContextualTypes.ts, 61, 33))
>cb : Symbol(cb, Decl(restTuplesFromContextualTypes.ts, 65, 22))
>a : Symbol(a, Decl(restTuplesFromContextualTypes.ts, 65, 27))
>b : Symbol(b, Decl(restTuplesFromContextualTypes.ts, 65, 37))
>take : Symbol(take, Decl(restTuplesFromContextualTypes.ts, 76, 33))
>cb : Symbol(cb, Decl(restTuplesFromContextualTypes.ts, 80, 22))
>a : Symbol(a, Decl(restTuplesFromContextualTypes.ts, 80, 27))
>b : Symbol(b, Decl(restTuplesFromContextualTypes.ts, 80, 37))

(function foo(...rest){}(1, ''));
>foo : Symbol(foo, Decl(restTuplesFromContextualTypes.ts, 67, 1))
>rest : Symbol(rest, Decl(restTuplesFromContextualTypes.ts, 67, 14))
>foo : Symbol(foo, Decl(restTuplesFromContextualTypes.ts, 82, 1))
>rest : Symbol(rest, Decl(restTuplesFromContextualTypes.ts, 82, 14))

take(function(...rest){});
>take : Symbol(take, Decl(restTuplesFromContextualTypes.ts, 61, 33))
>rest : Symbol(rest, Decl(restTuplesFromContextualTypes.ts, 68, 14))
>take : Symbol(take, Decl(restTuplesFromContextualTypes.ts, 76, 33))
>rest : Symbol(rest, Decl(restTuplesFromContextualTypes.ts, 83, 14))

// Repro from #29833

type ArgsUnion = [number, string] | [number, Error];
>ArgsUnion : Symbol(ArgsUnion, Decl(restTuplesFromContextualTypes.ts, 68, 26))
>ArgsUnion : Symbol(ArgsUnion, Decl(restTuplesFromContextualTypes.ts, 83, 26))
>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

type TupleUnionFunc = (...params: ArgsUnion) => number;
>TupleUnionFunc : Symbol(TupleUnionFunc, Decl(restTuplesFromContextualTypes.ts, 72, 52))
>params : Symbol(params, Decl(restTuplesFromContextualTypes.ts, 73, 23))
>ArgsUnion : Symbol(ArgsUnion, Decl(restTuplesFromContextualTypes.ts, 68, 26))
>TupleUnionFunc : Symbol(TupleUnionFunc, Decl(restTuplesFromContextualTypes.ts, 87, 52))
>params : Symbol(params, Decl(restTuplesFromContextualTypes.ts, 88, 23))
>ArgsUnion : Symbol(ArgsUnion, Decl(restTuplesFromContextualTypes.ts, 83, 26))

const funcUnionTupleNoRest: TupleUnionFunc = (num, strOrErr) => {
>funcUnionTupleNoRest : Symbol(funcUnionTupleNoRest, Decl(restTuplesFromContextualTypes.ts, 75, 5))
>TupleUnionFunc : Symbol(TupleUnionFunc, Decl(restTuplesFromContextualTypes.ts, 72, 52))
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 75, 46))
>strOrErr : Symbol(strOrErr, Decl(restTuplesFromContextualTypes.ts, 75, 50))
>funcUnionTupleNoRest : Symbol(funcUnionTupleNoRest, Decl(restTuplesFromContextualTypes.ts, 90, 5))
>TupleUnionFunc : Symbol(TupleUnionFunc, Decl(restTuplesFromContextualTypes.ts, 87, 52))
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 90, 46))
>strOrErr : Symbol(strOrErr, Decl(restTuplesFromContextualTypes.ts, 90, 50))

return num;
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 75, 46))
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 90, 46))

};

const funcUnionTupleRest: TupleUnionFunc = (...params) => {
>funcUnionTupleRest : Symbol(funcUnionTupleRest, Decl(restTuplesFromContextualTypes.ts, 79, 5))
>TupleUnionFunc : Symbol(TupleUnionFunc, Decl(restTuplesFromContextualTypes.ts, 72, 52))
>params : Symbol(params, Decl(restTuplesFromContextualTypes.ts, 79, 44))
>funcUnionTupleRest : Symbol(funcUnionTupleRest, Decl(restTuplesFromContextualTypes.ts, 94, 5))
>TupleUnionFunc : Symbol(TupleUnionFunc, Decl(restTuplesFromContextualTypes.ts, 87, 52))
>params : Symbol(params, Decl(restTuplesFromContextualTypes.ts, 94, 44))

const [num, strOrErr] = params;
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 80, 9))
>strOrErr : Symbol(strOrErr, Decl(restTuplesFromContextualTypes.ts, 80, 13))
>params : Symbol(params, Decl(restTuplesFromContextualTypes.ts, 79, 44))
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 95, 9))
>strOrErr : Symbol(strOrErr, Decl(restTuplesFromContextualTypes.ts, 95, 13))
>params : Symbol(params, Decl(restTuplesFromContextualTypes.ts, 94, 44))

return num;
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 80, 9))
>num : Symbol(num, Decl(restTuplesFromContextualTypes.ts, 95, 9))

};

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