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Narrow non-directly related weak types by intersecting them with candidates #58520

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Narrow non-directly related weak types by intersecting them with candidates #58520

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01bd4e8
Narrow non-directly related weak types by intersecting them with cand…
Andarist May 13, 2024
86863a7
Merge remote-tracking branch 'origin/main' into intersect-weak-types-…
Andarist Jan 16, 2025
73b5904
add test case
Andarist Jan 16, 2025
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4 changes: 2 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -28787,9 +28787,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
t => isTypeStrictSubtypeOf(t, c) ? t : isTypeStrictSubtypeOf(c, t) ? c : isTypeSubtypeOf(t, c) ? t : isTypeSubtypeOf(c, t) ? c : neverType,
);
// If no constituents are directly related, create intersections for any generic constituents that
// are related by constraint.
// are related by constraint or when the type is weak.
return directlyRelated.flags & TypeFlags.Never ?
mapType(type, t => maybeTypeOfKind(t, TypeFlags.Instantiable) && isRelated(c, getBaseConstraintOfType(t) || unknownType) ? getIntersectionType([t, c]) : neverType) :
mapType(type, t => maybeTypeOfKind(t, TypeFlags.Instantiable) && isRelated(c, getBaseConstraintOfType(t) || unknownType) || isWeakType(type) ? getIntersectionType([t, c]) : neverType) :
directlyRelated;
});
// If filtering produced a non-empty type, return that. Otherwise, pick the most specific of the two
Expand Down
35 changes: 34 additions & 1 deletion tests/baselines/reference/typeGuardIntersectionTypes.js
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Original file line number Diff line number Diff line change
Expand Up @@ -111,7 +111,31 @@ function beastFoo(beast: Object) {
if (hasLegs(beast) && hasWings(beast)) {
beast; // Legged & Winged
}
}
}

// https://github.com/microsoft/TypeScript/issues/58518

interface A_58518 {
label?: string;
a?: string;
}

interface B_58518 {
label?: string;
b: boolean;
}

function isB_58518(thing: object): thing is B_58518 {
return "b" in thing;
}

function test_58518(thing: A_58518) {
thing.a;
if (isB_58518(thing)) {
thing.a;
}
}


//// [typeGuardIntersectionTypes.js]
function f1(obj) {
Expand Down Expand Up @@ -180,3 +204,12 @@ function beastFoo(beast) {
beast; // Legged & Winged
}
}
function isB_58518(thing) {
return "b" in thing;
}
function test_58518(thing) {
thing.a;
if (isB_58518(thing)) {
thing.a;
}
}
70 changes: 62 additions & 8 deletions tests/baselines/reference/typeGuardIntersectionTypes.symbols
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Original file line number Diff line number Diff line change
Expand Up @@ -178,37 +178,37 @@ function identifyBeast(beast: Beast) {
>beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))

if (beast.legs === 4) {
>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))

log(`pegasus - 4 legs, wings`);
>log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
}
else if (beast.legs === 2) {
>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))

log(`bird - 2 legs, wings`);
>log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
}
else {
log(`unknown - ${beast.legs} legs, wings`);
>log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
}
}

// All non-winged beasts with legs
else {
log(`manbearpig - ${beast.legs} legs, no wings`);
>log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
>beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
>legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
}
}

Expand Down Expand Up @@ -257,3 +257,57 @@ function beastFoo(beast: Object) {
>beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 99, 18))
}
}

// https://github.com/microsoft/TypeScript/issues/58518

interface A_58518 {
>A_58518 : Symbol(A_58518, Decl(typeGuardIntersectionTypes.ts, 110, 1))

label?: string;
>label : Symbol(A_58518.label, Decl(typeGuardIntersectionTypes.ts, 114, 19))

a?: string;
>a : Symbol(A_58518.a, Decl(typeGuardIntersectionTypes.ts, 115, 17))
}

interface B_58518 {
>B_58518 : Symbol(B_58518, Decl(typeGuardIntersectionTypes.ts, 117, 1))

label?: string;
>label : Symbol(B_58518.label, Decl(typeGuardIntersectionTypes.ts, 119, 19))

b: boolean;
>b : Symbol(B_58518.b, Decl(typeGuardIntersectionTypes.ts, 120, 17))
}

function isB_58518(thing: object): thing is B_58518 {
>isB_58518 : Symbol(isB_58518, Decl(typeGuardIntersectionTypes.ts, 122, 1))
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 124, 19))
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 124, 19))
>B_58518 : Symbol(B_58518, Decl(typeGuardIntersectionTypes.ts, 117, 1))

return "b" in thing;
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 124, 19))
}

function test_58518(thing: A_58518) {
>test_58518 : Symbol(test_58518, Decl(typeGuardIntersectionTypes.ts, 126, 1))
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 128, 20))
>A_58518 : Symbol(A_58518, Decl(typeGuardIntersectionTypes.ts, 110, 1))

thing.a;
>thing.a : Symbol(A_58518.a, Decl(typeGuardIntersectionTypes.ts, 115, 17))
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 128, 20))
>a : Symbol(A_58518.a, Decl(typeGuardIntersectionTypes.ts, 115, 17))

if (isB_58518(thing)) {
>isB_58518 : Symbol(isB_58518, Decl(typeGuardIntersectionTypes.ts, 122, 1))
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 128, 20))

thing.a;
>thing.a : Symbol(A_58518.a, Decl(typeGuardIntersectionTypes.ts, 115, 17))
>thing : Symbol(thing, Decl(typeGuardIntersectionTypes.ts, 128, 20))
>a : Symbol(A_58518.a, Decl(typeGuardIntersectionTypes.ts, 115, 17))
}
}

90 changes: 80 additions & 10 deletions tests/baselines/reference/typeGuardIntersectionTypes.types
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Original file line number Diff line number Diff line change
Expand Up @@ -241,16 +241,16 @@ function identifyBeast(beast: Beast) {
> : ^^^^^^^
>hasWings : (x: Beast) => x is Winged
> : ^ ^^ ^^^^^^^^^^^^^^^^
>beast : Legged
> : ^^^^^^
>beast : Beast & Legged
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This is essentially the same test case as the added one. Without the change, we can't access beast.wings here (even though it's permitted before narrowing).

Regardless of that, I find it useful to include the @danvk's test case here as I could include the ticket reference in a clean manner above it.

> : ^^^^^^^^^^^^^^

if (beast.legs === 4) {
>beast.legs === 4 : boolean
> : ^^^^^^^
>beast.legs : number
> : ^^^^^^
>beast : Legged & Winged
> : ^^^^^^^^^^^^^^^
>beast : Beast & Legged & Winged
> : ^^^^^^^^^^^^^^^^^^^^^^^
>legs : number
> : ^^^^^^
>4 : 4
Expand All @@ -269,8 +269,8 @@ function identifyBeast(beast: Beast) {
> : ^^^^^^^
>beast.legs : number
> : ^^^^^^
>beast : Legged & Winged
> : ^^^^^^^^^^^^^^^
>beast : Beast & Legged & Winged
> : ^^^^^^^^^^^^^^^^^^^^^^^
>legs : number
> : ^^^^^^
>2 : 2
Expand All @@ -294,8 +294,8 @@ function identifyBeast(beast: Beast) {
> : ^^^^^^
>beast.legs : number
> : ^^^^^^
>beast : Legged & Winged
> : ^^^^^^^^^^^^^^^
>beast : Beast & Legged & Winged
> : ^^^^^^^^^^^^^^^^^^^^^^^
>legs : number
> : ^^^^^^
}
Expand All @@ -312,8 +312,8 @@ function identifyBeast(beast: Beast) {
> : ^^^^^^
>beast.legs : number
> : ^^^^^^
>beast : Legged
> : ^^^^^^
>beast : Beast & Legged
> : ^^^^^^^^^^^^^^
>legs : number
> : ^^^^^^
}
Expand Down Expand Up @@ -402,3 +402,73 @@ function beastFoo(beast: Object) {
> : ^^^^^^^^^^^^^^^
}
}

// https://github.com/microsoft/TypeScript/issues/58518

interface A_58518 {
label?: string;
>label : string | undefined
> : ^^^^^^^^^^^^^^^^^^

a?: string;
>a : string | undefined
> : ^^^^^^^^^^^^^^^^^^
}

interface B_58518 {
label?: string;
>label : string | undefined
> : ^^^^^^^^^^^^^^^^^^

b: boolean;
>b : boolean
> : ^^^^^^^
}

function isB_58518(thing: object): thing is B_58518 {
>isB_58518 : (thing: object) => thing is B_58518
> : ^ ^^ ^^^^^
>thing : object
> : ^^^^^^

return "b" in thing;
>"b" in thing : boolean
> : ^^^^^^^
>"b" : "b"
> : ^^^
>thing : object
> : ^^^^^^
}

function test_58518(thing: A_58518) {
>test_58518 : (thing: A_58518) => void
> : ^ ^^ ^^^^^^^^^
>thing : A_58518
> : ^^^^^^^

thing.a;
>thing.a : string | undefined
> : ^^^^^^^^^^^^^^^^^^
>thing : A_58518
> : ^^^^^^^
>a : string | undefined
> : ^^^^^^^^^^^^^^^^^^

if (isB_58518(thing)) {
>isB_58518(thing) : boolean
> : ^^^^^^^
>isB_58518 : (thing: object) => thing is B_58518
> : ^ ^^ ^^^^^^^^^^^^^^^^^^^^^
>thing : A_58518
> : ^^^^^^^

thing.a;
>thing.a : string | undefined
> : ^^^^^^^^^^^^^^^^^^
>thing : A_58518 & B_58518
> : ^^^^^^^^^^^^^^^^^
>a : string | undefined
> : ^^^^^^^^^^^^^^^^^^
}
}

25 changes: 24 additions & 1 deletion tests/cases/conformance/expressions/typeGuards/typeGuardIntersectionTypes.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -110,4 +110,27 @@ function beastFoo(beast: Object) {
if (hasLegs(beast) && hasWings(beast)) {
beast; // Legged & Winged
}
}
}

// https://github.com/microsoft/TypeScript/issues/58518

interface A_58518 {
label?: string;
a?: string;
}

interface B_58518 {
label?: string;
b: boolean;
}

function isB_58518(thing: object): thing is B_58518 {
return "b" in thing;
}

function test_58518(thing: A_58518) {
thing.a;
if (isB_58518(thing)) {
thing.a;
}
}