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Normalize union/intersection type combinations #11717

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Oct 19, 2016
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Normalize union/intersection type combinations #11717

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ef5f3c9
Normalize intersection and union types
ahejlsberg Oct 18, 2016
eb7d2cb
Accept new baselines
ahejlsberg Oct 18, 2016
6a0f729
Simplify logic in checkTypeRelatedTo
ahejlsberg Oct 18, 2016
bf7f2e2
Add tests
ahejlsberg Oct 18, 2016
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70 changes: 39 additions & 31 deletions src/compiler/checker.ts
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Expand Up @@ -5603,6 +5603,11 @@ namespace ts {
}
}

// We normalize combinations of intersection and union types based on the distributive property of the '&'
// operator. Specifically, because X & (A | B) is equivalent to X & A | X & B, we can transform intersection
// types with union type constituents into equivalent union types with intersection type constituents and
// effectively ensure that union types are always at the top level in type representations.
//
// We do not perform structural deduplication on intersection types. Intersection types are created only by the &
// type operator and we can't reduce those because we want to support recursive intersection types. For example,
// a type alias of the form "type List<T> = T & { next: List<T> }" cannot be reduced during its declaration.
Expand All @@ -5612,6 +5617,15 @@ namespace ts {
if (types.length === 0) {
return emptyObjectType;
}
for (let i = 0; i < types.length; i++) {
const type = types[i];
if (type.flags & TypeFlags.Union) {
// We are attempting to construct a type of the form X & (A | B) & Y. Transform this into a type of
// the form X & A & Y | X & B & Y and recursively reduce until no union type constituents remain.
return getUnionType(map((<UnionType>type).types, t => getIntersectionType(replaceElement(types, i, t))),
/*subtypeReduction*/ false, aliasSymbol, aliasTypeArguments);
}
}
const typeSet = [] as TypeSet;
addTypesToIntersection(typeSet, types);
if (typeSet.containsAny) {
Expand Down Expand Up @@ -6559,52 +6573,46 @@ namespace ts {

const saveErrorInfo = errorInfo;

// Note that these checks are specifically ordered to produce correct results.
// Note that these checks are specifically ordered to produce correct results. In particular,
// we need to deconstruct unions before intersections (because unions are always at the top),
// and we need to handle "each" relations before "some" relations for the same kind of type.
if (source.flags & TypeFlags.Union) {
if (relation === comparableRelation) {
result = someTypeRelatedToType(source as UnionType, target, reportErrors && !(source.flags & TypeFlags.Primitive));
}
else {
result = eachTypeRelatedToType(source as UnionType, target, reportErrors && !(source.flags & TypeFlags.Primitive));
}

if (result) {
return result;
}
}
else if (target.flags & TypeFlags.Intersection) {
result = typeRelatedToEachType(source, target as IntersectionType, reportErrors);

if (result) {
else if (target.flags & TypeFlags.Union) {
if (result = typeRelatedToSomeType(source, <UnionType>target, reportErrors && !(source.flags & TypeFlags.Primitive) && !(target.flags & TypeFlags.Primitive))) {
return result;
}
}
else {
// It is necessary to try these "some" checks on both sides because there may be nested "each" checks
// on either side that need to be prioritized. For example, A | B = (A | B) & (C | D) or
// A & B = (A & B) | (C & D).
if (source.flags & TypeFlags.Intersection) {
// Check to see if any constituents of the intersection are immediately related to the target.
//
// Don't report errors though. Checking whether a constituent is related to the source is not actually
// useful and leads to some confusing error messages. Instead it is better to let the below checks
// take care of this, or to not elaborate at all. For instance,
//
// - For an object type (such as 'C = A & B'), users are usually more interested in structural errors.
//
// - For a union type (such as '(A | B) = (C & D)'), it's better to hold onto the whole intersection
// than to report that 'D' is not assignable to 'A' or 'B'.
//
// - For a primitive type or type parameter (such as 'number = A & B') there is no point in
// breaking the intersection apart.
if (result = someTypeRelatedToType(<IntersectionType>source, target, /*reportErrors*/ false)) {
return result;
}
else if (target.flags & TypeFlags.Intersection) {
if (result = typeRelatedToEachType(source, target as IntersectionType, reportErrors)) {
return result;
}
if (target.flags & TypeFlags.Union) {
if (result = typeRelatedToSomeType(source, <UnionType>target, reportErrors && !(source.flags & TypeFlags.Primitive) && !(target.flags & TypeFlags.Primitive))) {
return result;
}
}
else if (source.flags & TypeFlags.Intersection) {
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why not check the source first here too? I think that's the normal pattern for isRelatedTo

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The comment above the initial if statement explains why. For intersection types, the target side is an "each" relationship and the source side is a "some" relationship. We need to deconstruct "each" relationships first to get the correct results.

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OK, so I think I misunderstood the parts of the code that are independent post-distribution. It would work to put intersections before unions now, where it wouldn't before, right?

// Check to see if any constituents of the intersection are immediately related to the target.
//
// Don't report errors though. Checking whether a constituent is related to the source is not actually
// useful and leads to some confusing error messages. Instead it is better to let the below checks
// take care of this, or to not elaborate at all. For instance,
//
// - For an object type (such as 'C = A & B'), users are usually more interested in structural errors.
//
// - For a union type (such as '(A | B) = (C & D)'), it's better to hold onto the whole intersection
// than to report that 'D' is not assignable to 'A' or 'B'.
//
// - For a primitive type or type parameter (such as 'number = A & B') there is no point in
// breaking the intersection apart.
if (result = someTypeRelatedToType(<IntersectionType>source, target, /*reportErrors*/ false)) {
return result;
}
}

Expand Down
6 changes: 6 additions & 0 deletions src/compiler/core.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -532,6 +532,12 @@ namespace ts {
: undefined;
}

export function replaceElement<T>(array: T[], index: number, value: T): T[] {
const result = array.slice(0);
result[index] = value;
return result;
}

/**
* Performs a binary search, finding the index at which 'value' occurs in 'array'.
* If no such index is found, returns the 2's-complement of first index at which
Expand Down
6 changes: 4 additions & 2 deletions tests/baselines/reference/errorMessagesIntersectionTypes04.errors.txt
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@@ -1,7 +1,8 @@
tests/cases/compiler/errorMessagesIntersectionTypes04.ts(17,5): error TS2322: Type 'A & B' is not assignable to type 'number'.
tests/cases/compiler/errorMessagesIntersectionTypes04.ts(18,5): error TS2322: Type 'A & B' is not assignable to type 'boolean'.
tests/cases/compiler/errorMessagesIntersectionTypes04.ts(19,5): error TS2322: Type 'A & B' is not assignable to type 'string'.
tests/cases/compiler/errorMessagesIntersectionTypes04.ts(21,5): error TS2322: Type 'number & boolean' is not assignable to type 'string'.
tests/cases/compiler/errorMessagesIntersectionTypes04.ts(21,5): error TS2322: Type '(number & true) | (number & false)' is not assignable to type 'string'.
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Is there some way to present this error as number & boolean still? I feel like the distributed form is unexpected here.

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The actual representation needs to be (number & true) | (number & false), but we could play tricks in the type-to-string logic to turn it into number & boolean. Not sure it's worth it though as those types are all rather meaningless anyway.

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Yeah, type-to-string is what I was thinking of. But you're right, & boolean probably only shows up in our tests.

Type 'number & true' is not assignable to type 'string'.


==== tests/cases/compiler/errorMessagesIntersectionTypes04.ts (4 errors) ====
Expand Down Expand Up @@ -33,5 +34,6 @@ tests/cases/compiler/errorMessagesIntersectionTypes04.ts(21,5): error TS2322: Ty

str = num_and_bool;
~~~
!!! error TS2322: Type 'number & boolean' is not assignable to type 'string'.
!!! error TS2322: Type '(number & true) | (number & false)' is not assignable to type 'string'.
!!! error TS2322: Type 'number & true' is not assignable to type 'string'.
}
74 changes: 38 additions & 36 deletions tests/baselines/reference/intersectionAndUnionTypes.errors.txt
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Expand Up @@ -30,28 +30,29 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(29,1): e
Type 'A & B' is not assignable to type 'C | D'.
Type 'A & B' is not assignable to type 'D'.
Property 'd' is missing in type 'A & B'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(31,1): error TS2322: Type 'A & B' is not assignable to type '(A | B) & (C | D)'.
Type 'A & B' is not assignable to type 'C | D'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(31,1): error TS2322: Type 'A & B' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
Type 'A & B' is not assignable to type 'B & D'.
Type 'A & B' is not assignable to type 'D'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(32,1): error TS2322: Type 'A | B' is not assignable to type '(A | B) & (C | D)'.
Type 'A' is not assignable to type '(A | B) & (C | D)'.
Type 'A' is not assignable to type 'C | D'.
Type 'A' is not assignable to type 'D'.
Property 'd' is missing in type 'A'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(33,1): error TS2322: Type 'C & D' is not assignable to type '(A | B) & (C | D)'.
Type 'C & D' is not assignable to type 'A | B'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(32,1): error TS2322: Type 'A | B' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
Type 'A' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
Type 'A' is not assignable to type 'B & D'.
Type 'A' is not assignable to type 'B'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(33,1): error TS2322: Type 'C & D' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
Type 'C & D' is not assignable to type 'B & D'.
Type 'C & D' is not assignable to type 'B'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(34,1): error TS2322: Type 'C | D' is not assignable to type '(A | B) & (C | D)'.
Type 'C' is not assignable to type '(A | B) & (C | D)'.
Type 'C' is not assignable to type 'A | B'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(34,1): error TS2322: Type 'C | D' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
Type 'C' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
Type 'C' is not assignable to type 'B & D'.
Type 'C' is not assignable to type 'B'.
Property 'b' is missing in type 'C'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(35,1): error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'A & B'.
Type '(A | B) & (C | D)' is not assignable to type 'A'.
Property 'a' is missing in type '(A | B) & (C | D)'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'C & D'.
Type '(A | B) & (C | D)' is not assignable to type 'C'.
Property 'c' is missing in type '(A | B) & (C | D)'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(35,1): error TS2322: Type '(A & C) | (A & D) | (B & C) | (B & D)' is not assignable to type 'A & B'.
Type 'A & C' is not assignable to type 'A & B'.
Type 'A & C' is not assignable to type 'B'.
Property 'b' is missing in type 'A & C'.
tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): error TS2322: Type '(A & C) | (A & D) | (B & C) | (B & D)' is not assignable to type 'C & D'.
Type 'A & C' is not assignable to type 'C & D'.
Type 'A & C' is not assignable to type 'D'.
Property 'd' is missing in type 'A & C'.


==== tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts (14 errors) ====
Expand Down Expand Up @@ -127,38 +128,39 @@ tests/cases/conformance/types/intersection/intersectionAndUnionTypes.ts(37,1): e

y = anb;
~
!!! error TS2322: Type 'A & B' is not assignable to type '(A | B) & (C | D)'.
!!! error TS2322: Type 'A & B' is not assignable to type 'C | D'.
!!! error TS2322: Type 'A & B' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
!!! error TS2322: Type 'A & B' is not assignable to type 'B & D'.
!!! error TS2322: Type 'A & B' is not assignable to type 'D'.
y = aob;
~
!!! error TS2322: Type 'A | B' is not assignable to type '(A | B) & (C | D)'.
!!! error TS2322: Type 'A' is not assignable to type '(A | B) & (C | D)'.
!!! error TS2322: Type 'A' is not assignable to type 'C | D'.
!!! error TS2322: Type 'A' is not assignable to type 'D'.
!!! error TS2322: Property 'd' is missing in type 'A'.
!!! error TS2322: Type 'A | B' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
!!! error TS2322: Type 'A' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
!!! error TS2322: Type 'A' is not assignable to type 'B & D'.
!!! error TS2322: Type 'A' is not assignable to type 'B'.
y = cnd;
~
!!! error TS2322: Type 'C & D' is not assignable to type '(A | B) & (C | D)'.
!!! error TS2322: Type 'C & D' is not assignable to type 'A | B'.
!!! error TS2322: Type 'C & D' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
!!! error TS2322: Type 'C & D' is not assignable to type 'B & D'.
!!! error TS2322: Type 'C & D' is not assignable to type 'B'.
y = cod;
~
!!! error TS2322: Type 'C | D' is not assignable to type '(A | B) & (C | D)'.
!!! error TS2322: Type 'C' is not assignable to type '(A | B) & (C | D)'.
!!! error TS2322: Type 'C' is not assignable to type 'A | B'.
!!! error TS2322: Type 'C | D' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
!!! error TS2322: Type 'C' is not assignable to type '(A & C) | (A & D) | (B & C) | (B & D)'.
!!! error TS2322: Type 'C' is not assignable to type 'B & D'.
!!! error TS2322: Type 'C' is not assignable to type 'B'.
!!! error TS2322: Property 'b' is missing in type 'C'.
anb = y;
~~~
!!! error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'A & B'.
!!! error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'A'.
!!! error TS2322: Property 'a' is missing in type '(A | B) & (C | D)'.
!!! error TS2322: Type '(A & C) | (A & D) | (B & C) | (B & D)' is not assignable to type 'A & B'.
!!! error TS2322: Type 'A & C' is not assignable to type 'A & B'.
!!! error TS2322: Type 'A & C' is not assignable to type 'B'.
!!! error TS2322: Property 'b' is missing in type 'A & C'.
aob = y; // Ok
cnd = y;
~~~
!!! error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'C & D'.
!!! error TS2322: Type '(A | B) & (C | D)' is not assignable to type 'C'.
!!! error TS2322: Property 'c' is missing in type '(A | B) & (C | D)'.
!!! error TS2322: Type '(A & C) | (A & D) | (B & C) | (B & D)' is not assignable to type 'C & D'.
!!! error TS2322: Type 'A & C' is not assignable to type 'C & D'.
!!! error TS2322: Type 'A & C' is not assignable to type 'D'.
!!! error TS2322: Property 'd' is missing in type 'A & C'.
cod = y; // Ok

79 changes: 79 additions & 0 deletions tests/baselines/reference/intersectionTypeNormalization.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
//// [intersectionTypeNormalization.ts]
interface A { a: string }
interface B { b: string }
interface C { c: string }
interface D { d: string }

// Identical ways of writing the same type
type X1 = (A | B) & (C | D);
type X2 = A & (C | D) | B & (C | D)
type X3 = A & C | A & D | B & C | B & D;

var x: X1;
var x: X2;
var x: X3;

interface X { x: string }
interface Y { y: string }

// Identical ways of writing the same type
type Y1 = (A | X & Y) & (C | D);
type Y2 = A & (C | D) | X & Y & (C | D)
type Y3 = A & C | A & D | X & Y & C | X & Y & D;

var y: Y1;
var y: Y2;
var y: Y3;

interface M { m: string }
interface N { n: string }

// Identical ways of writing the same type
type Z1 = (A | X & (M | N)) & (C | D);
type Z2 = A & (C | D) | X & (M | N) & (C | D)
type Z3 = A & C | A & D | X & (M | N) & C | X & (M | N) & D;
type Z4 = A & C | A & D | X & M & C | X & N & C | X & M & D | X & N & D;

var z: Z1;
var z: Z2;
var z: Z3;
var z: Z4;

// Repro from #9919

type ToString = {
toString(): string;
}

type BoxedValue = { kind: 'int', num: number }
| { kind: 'string', str: string }

type IntersectionFail = BoxedValue & ToString

type IntersectionInline = { kind: 'int', num: number } & ToString
| { kind: 'string', str: string } & ToString

function getValueAsString(value: IntersectionFail): string {
if (value.kind === 'int') {
return '' + value.num;
}
return value.str;
}

//// [intersectionTypeNormalization.js]
var x;
var x;
var x;
var y;
var y;
var y;
var z;
var z;
var z;
var z;
function getValueAsString(value) {
if (value.kind === 'int') {
return '' + value.num;
}
return value.str;
}
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