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Fix empty array inference #19912

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Nov 10, 2017
Merged

Fix empty array inference #19912

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2010c4c
Give lowest priority to inferences made from empty array literals
ahejlsberg Nov 10, 2017
197c635
Update tests
ahejlsberg Nov 10, 2017
afec1e1
Update test
ahejlsberg Nov 10, 2017
2c43ef1
Accept new baselines
ahejlsberg Nov 10, 2017
c3b650f
Accept API baseline changes
ahejlsberg Nov 10, 2017
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17 changes: 10 additions & 7 deletions src/compiler/checker.ts
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Expand Up @@ -10898,22 +10898,25 @@ namespace ts {
// it as an inference candidate. Hopefully, a better candidate will come along that does
// not contain anyFunctionType when we come back to this argument for its second round
// of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
// when constructing types from type parameters that had no inference candidates) and
// implicitNeverType (which is used as the element type for empty array literals).
if (source.flags & TypeFlags.ContainsAnyFunctionType || source === silentNeverType || source === implicitNeverType) {
// when constructing types from type parameters that had no inference candidates).
if (source.flags & TypeFlags.ContainsAnyFunctionType || source === silentNeverType) {
return;
}
const inference = getInferenceInfoForType(target);
if (inference) {
if (!inference.isFixed) {
if (!inference.candidates || priority < inference.priority) {
// We give lowest priority to inferences of implicitNeverType (which is used as the
// element type for empty array literals). Thus, inferences from empty array literals
// only matter when no other inferences are made.
const p = priority | (source === implicitNeverType ? InferencePriority.NeverType : 0);
if (!inference.candidates || p < inference.priority) {
inference.candidates = [source];
inference.priority = priority;
inference.priority = p;
}
else if (priority === inference.priority) {
else if (p === inference.priority) {
inference.candidates.push(source);
}
if (!(priority & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {
if (!(p & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {
inference.topLevel = false;
}
}
Expand Down
1 change: 1 addition & 0 deletions src/compiler/types.ts
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Expand Up @@ -3613,6 +3613,7 @@ namespace ts {
NakedTypeVariable = 1 << 1, // Naked type variable in union or intersection type
MappedType = 1 << 2, // Reverse inference for mapped type
ReturnType = 1 << 3, // Inference made from return type of generic function
NeverType = 1 << 4, // Inference made from the never type
}

export interface InferenceInfo {
Expand Down
1 change: 1 addition & 0 deletions tests/baselines/reference/api/tsserverlibrary.d.ts
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Expand Up @@ -2142,6 +2142,7 @@ declare namespace ts {
NakedTypeVariable = 2,
MappedType = 4,
ReturnType = 8,
NeverType = 16,
}
interface InferenceInfo {
typeParameter: TypeParameter;
Expand Down
1 change: 1 addition & 0 deletions tests/baselines/reference/api/typescript.d.ts
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Expand Up @@ -2142,6 +2142,7 @@ declare namespace ts {
NakedTypeVariable = 2,
MappedType = 4,
ReturnType = 8,
NeverType = 16,
}
interface InferenceInfo {
typeParameter: TypeParameter;
Expand Down
22 changes: 15 additions & 7 deletions tests/baselines/reference/neverInference.js
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@@ -1,10 +1,10 @@
//// [neverInference.ts]
declare function f<T>(x: T[]): T;
declare function f1<T>(x: T[]): T;

let neverArray: never[] = [];

let a1 = f([]); // {}
let a2 = f(neverArray); // never
let a1 = f1([]); // never
let a2 = f1(neverArray); // never

// Repro from #19576

Expand All @@ -21,11 +21,19 @@ declare function compareNumbers(x: number, y: number): number;
declare function mkList<T>(items: T[], comparator: Comparator<T>): LinkedList<T>;

const list: LinkedList<number> = mkList([], compareNumbers);

// Repro from #19858

declare function f2<a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number): void;
f2(Array.from([0]), [], (a1, a2) => a1 - a2);
f2(Array.from([]), [0], (a1, a2) => a1 - a2);


//// [neverInference.js]
"use strict";
var neverArray = [];
var a1 = f([]); // {}
var a2 = f(neverArray); // never
var list = mkList([], compareNumbers);
let neverArray = [];
let a1 = f1([]); // never
let a2 = f1(neverArray); // never
const list = mkList([], compareNumbers);
f2(Array.from([0]), [], (a1, a2) => a1 - a2);
f2(Array.from([]), [0], (a1, a2) => a1 - a2);
61 changes: 48 additions & 13 deletions tests/baselines/reference/neverInference.symbols
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@@ -1,27 +1,27 @@
=== tests/cases/conformance/types/never/neverInference.ts ===
declare function f<T>(x: T[]): T;
>f : Symbol(f, Decl(neverInference.ts, 0, 0))
>T : Symbol(T, Decl(neverInference.ts, 0, 19))
>x : Symbol(x, Decl(neverInference.ts, 0, 22))
>T : Symbol(T, Decl(neverInference.ts, 0, 19))
>T : Symbol(T, Decl(neverInference.ts, 0, 19))
declare function f1<T>(x: T[]): T;
>f1 : Symbol(f1, Decl(neverInference.ts, 0, 0))
>T : Symbol(T, Decl(neverInference.ts, 0, 20))
>x : Symbol(x, Decl(neverInference.ts, 0, 23))
>T : Symbol(T, Decl(neverInference.ts, 0, 20))
>T : Symbol(T, Decl(neverInference.ts, 0, 20))

let neverArray: never[] = [];
>neverArray : Symbol(neverArray, Decl(neverInference.ts, 2, 3))

let a1 = f([]); // {}
let a1 = f1([]); // never
>a1 : Symbol(a1, Decl(neverInference.ts, 4, 3))
>f : Symbol(f, Decl(neverInference.ts, 0, 0))
>f1 : Symbol(f1, Decl(neverInference.ts, 0, 0))

let a2 = f(neverArray); // never
let a2 = f1(neverArray); // never
>a2 : Symbol(a2, Decl(neverInference.ts, 5, 3))
>f : Symbol(f, Decl(neverInference.ts, 0, 0))
>f1 : Symbol(f1, Decl(neverInference.ts, 0, 0))
>neverArray : Symbol(neverArray, Decl(neverInference.ts, 2, 3))

// Repro from #19576

type Comparator<T> = (x: T, y: T) => number;
>Comparator : Symbol(Comparator, Decl(neverInference.ts, 5, 23))
>Comparator : Symbol(Comparator, Decl(neverInference.ts, 5, 24))
>T : Symbol(T, Decl(neverInference.ts, 9, 16))
>x : Symbol(x, Decl(neverInference.ts, 9, 22))
>T : Symbol(T, Decl(neverInference.ts, 9, 16))
Expand All @@ -34,7 +34,7 @@ interface LinkedList<T> {

comparator: Comparator<T>,
>comparator : Symbol(LinkedList.comparator, Decl(neverInference.ts, 11, 25))
>Comparator : Symbol(Comparator, Decl(neverInference.ts, 5, 23))
>Comparator : Symbol(Comparator, Decl(neverInference.ts, 5, 24))
>T : Symbol(T, Decl(neverInference.ts, 11, 21))

nodes: Node<T>
Expand Down Expand Up @@ -63,7 +63,7 @@ declare function mkList<T>(items: T[], comparator: Comparator<T>): LinkedList<T>
>items : Symbol(items, Decl(neverInference.ts, 19, 27))
>T : Symbol(T, Decl(neverInference.ts, 19, 24))
>comparator : Symbol(comparator, Decl(neverInference.ts, 19, 38))
>Comparator : Symbol(Comparator, Decl(neverInference.ts, 5, 23))
>Comparator : Symbol(Comparator, Decl(neverInference.ts, 5, 24))
>T : Symbol(T, Decl(neverInference.ts, 19, 24))
>LinkedList : Symbol(LinkedList, Decl(neverInference.ts, 9, 44))
>T : Symbol(T, Decl(neverInference.ts, 19, 24))
Expand All @@ -74,3 +74,38 @@ const list: LinkedList<number> = mkList([], compareNumbers);
>mkList : Symbol(mkList, Decl(neverInference.ts, 18, 62))
>compareNumbers : Symbol(compareNumbers, Decl(neverInference.ts, 16, 49))

// Repro from #19858

declare function f2<a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number): void;
>f2 : Symbol(f2, Decl(neverInference.ts, 21, 60))
>a : Symbol(a, Decl(neverInference.ts, 25, 20))
>as1 : Symbol(as1, Decl(neverInference.ts, 25, 23))
>a : Symbol(a, Decl(neverInference.ts, 25, 20))
>as2 : Symbol(as2, Decl(neverInference.ts, 25, 32))
>a : Symbol(a, Decl(neverInference.ts, 25, 20))
>cmp : Symbol(cmp, Decl(neverInference.ts, 25, 42))
>a1 : Symbol(a1, Decl(neverInference.ts, 25, 49))
>a : Symbol(a, Decl(neverInference.ts, 25, 20))
>a2 : Symbol(a2, Decl(neverInference.ts, 25, 55))
>a : Symbol(a, Decl(neverInference.ts, 25, 20))

f2(Array.from([0]), [], (a1, a2) => a1 - a2);
>f2 : Symbol(f2, Decl(neverInference.ts, 21, 60))
>Array.from : Symbol(ArrayConstructor.from, Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
>from : Symbol(ArrayConstructor.from, Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
>a1 : Symbol(a1, Decl(neverInference.ts, 26, 25))
>a2 : Symbol(a2, Decl(neverInference.ts, 26, 28))
>a1 : Symbol(a1, Decl(neverInference.ts, 26, 25))
>a2 : Symbol(a2, Decl(neverInference.ts, 26, 28))

f2(Array.from([]), [0], (a1, a2) => a1 - a2);
>f2 : Symbol(f2, Decl(neverInference.ts, 21, 60))
>Array.from : Symbol(ArrayConstructor.from, Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
>from : Symbol(ArrayConstructor.from, Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
>a1 : Symbol(a1, Decl(neverInference.ts, 27, 25))
>a2 : Symbol(a2, Decl(neverInference.ts, 27, 28))
>a1 : Symbol(a1, Decl(neverInference.ts, 27, 25))
>a2 : Symbol(a2, Decl(neverInference.ts, 27, 28))

67 changes: 58 additions & 9 deletions tests/baselines/reference/neverInference.types
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@@ -1,6 +1,6 @@
=== tests/cases/conformance/types/never/neverInference.ts ===
declare function f<T>(x: T[]): T;
>f : <T>(x: T[]) => T
declare function f1<T>(x: T[]): T;
>f1 : <T>(x: T[]) => T
>T : T
>x : T[]
>T : T
Expand All @@ -10,16 +10,16 @@ let neverArray: never[] = [];
>neverArray : never[]
>[] : never[]

let a1 = f([]); // {}
>a1 : {}
>f([]) : {}
>f : <T>(x: T[]) => T
let a1 = f1([]); // never
>a1 : never
>f1([]) : never
>f1 : <T>(x: T[]) => T
>[] : never[]

let a2 = f(neverArray); // never
let a2 = f1(neverArray); // never
>a2 : never
>f(neverArray) : never
>f : <T>(x: T[]) => T
>f1(neverArray) : never
>f1 : <T>(x: T[]) => T
>neverArray : never[]

// Repro from #19576
Expand Down Expand Up @@ -81,3 +81,52 @@ const list: LinkedList<number> = mkList([], compareNumbers);
>[] : never[]
>compareNumbers : (x: number, y: number) => number

// Repro from #19858

declare function f2<a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number): void;
>f2 : <a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number) => void
>a : a
>as1 : a[]
>a : a
>as2 : a[]
>a : a
>cmp : (a1: a, a2: a) => number
>a1 : a
>a : a
>a2 : a
>a : a

f2(Array.from([0]), [], (a1, a2) => a1 - a2);
>f2(Array.from([0]), [], (a1, a2) => a1 - a2) : void
>f2 : <a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number) => void
>Array.from([0]) : number[]
>Array.from : { <T>(iterable: Iterable<T>): T[]; <T, U>(iterable: Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
>Array : ArrayConstructor
>from : { <T>(iterable: Iterable<T>): T[]; <T, U>(iterable: Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
>[0] : number[]
>0 : 0
>[] : never[]
>(a1, a2) => a1 - a2 : (a1: number, a2: number) => number
>a1 : number
>a2 : number
>a1 - a2 : number
>a1 : number
>a2 : number

f2(Array.from([]), [0], (a1, a2) => a1 - a2);
>f2(Array.from([]), [0], (a1, a2) => a1 - a2) : void
>f2 : <a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number) => void
>Array.from([]) : never[]
>Array.from : { <T>(iterable: Iterable<T>): T[]; <T, U>(iterable: Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
>Array : ArrayConstructor
>from : { <T>(iterable: Iterable<T>): T[]; <T, U>(iterable: Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
>[] : never[]
>[0] : number[]
>0 : 0
>(a1, a2) => a1 - a2 : (a1: number, a2: number) => number
>a1 : number
>a2 : number
>a1 - a2 : number
>a1 : number
>a2 : number

13 changes: 10 additions & 3 deletions tests/cases/conformance/types/never/neverInference.ts
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Original file line number Diff line number Diff line change
@@ -1,11 +1,12 @@
// @strict: true
// @target: es2015

declare function f<T>(x: T[]): T;
declare function f1<T>(x: T[]): T;

let neverArray: never[] = [];

let a1 = f([]); // {}
let a2 = f(neverArray); // never
let a1 = f1([]); // never
let a2 = f1(neverArray); // never

// Repro from #19576

Expand All @@ -22,3 +23,9 @@ declare function compareNumbers(x: number, y: number): number;
declare function mkList<T>(items: T[], comparator: Comparator<T>): LinkedList<T>;

const list: LinkedList<number> = mkList([], compareNumbers);

// Repro from #19858

declare function f2<a>(as1: a[], as2: a[], cmp: (a1: a, a2: a) => number): void;
f2(Array.from([0]), [], (a1, a2) => a1 - a2);
f2(Array.from([]), [0], (a1, a2) => a1 - a2);