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Fix creation of composite union type predicates (#54169)
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@ahejlsberg
ahejlsberg committed May 19, 2023
1 parent 2b7d517 commit 215fe6e
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Showing 5 changed files with 439 additions and 18 deletions.
31 changes: 13 additions & 18 deletions src/compiler/checker.ts
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Expand Up @@ -16515,36 +16515,31 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}

function getUnionOrIntersectionTypePredicate(signatures: readonly Signature[], kind: TypeFlags | undefined): TypePredicate | undefined {
let first: TypePredicate | undefined;
let last: TypePredicate | undefined;
const types: Type[] = [];
for (const sig of signatures) {
const pred = getTypePredicateOfSignature(sig);
if (!pred || pred.kind === TypePredicateKind.AssertsThis || pred.kind === TypePredicateKind.AssertsIdentifier) {
if (kind !== TypeFlags.Intersection) {
continue;
}
else {
return; // intersections demand all members be type predicates for the result to have a predicate
}
}

if (first) {
if (!typePredicateKindsMatch(first, pred)) {
// No common type predicate.
if (pred) {
// Constituent type predicates must all have matching kinds. We don't create composite type predicates for assertions.
if (pred.kind !== TypePredicateKind.This && pred.kind !== TypePredicateKind.Identifier || last && !typePredicateKindsMatch(last, pred)) {
return undefined;
}
last = pred;
types.push(pred.type);
}
else {
first = pred;
// In composite union signatures we permit and ignore signatures with a return type `false`.
const returnType = kind !== TypeFlags.Intersection ? getReturnTypeOfSignature(sig) : undefined;
if (returnType !== falseType && returnType !== regularFalseType) {
return undefined;
}
}
types.push(pred.type);
}
if (!first) {
// No signatures had a type predicate.
if (!last) {
return undefined;
}
const compositeType = getUnionOrIntersectionType(types, kind);
return createTypePredicate(first.kind, first.parameterName, first.parameterIndex, compositeType);
return createTypePredicate(last.kind, last.parameterName, last.parameterIndex, compositeType);
}

function typePredicateKindsMatch(a: TypePredicate, b: TypePredicate): boolean {
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69 changes: 69 additions & 0 deletions tests/baselines/reference/typePredicatesInUnion3.errors.txt
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@@ -0,0 +1,69 @@
tests/cases/compiler/typePredicatesInUnion3.ts(59,24): error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number'.
Type 'null' is not assignable to type 'number'.


==== tests/cases/compiler/typePredicatesInUnion3.ts (1 errors) ====
// A union of function types is considered a type predicate if at least one constituent is a type
// predicate and the other constituents are matching type predicates or functions returning `false`.

type P1 = (x: unknown) => x is string;
type P2 = (x: unknown) => x is number;

type F1 = (x: unknown) => false;
type F2 = (x: unknown) => boolean;
type F3 = (x: unknown) => string;

function f1(x: unknown, p: P1 | P2) {
if (p(x)) {
x; // string | number
}
}

function f2(x: unknown, p: P1 | P2 | F1) {
if (p(x)) {
x; // string | number
}
}

function f3(x: unknown, p: P1 | P2 | F2) {
if (p(x)) {
x; // unknown
}
}

function f4(x: unknown, p: P1 | P2 | F3) {
if (p(x)) {
x; // unknown
}
}

// Repro from #54143

type HasAttribute<T> = T & { attribute: number };

class Type1 {
attribute: number | null = null;
predicate(): this is HasAttribute<Type1> {
return true;
}
}

class Type2 {
attribute: number | null = null;
predicate(): boolean {
return true;
}
}

function assertType<T>(_val: T) {
}

declare const val: Type1 | Type2;

if (val.predicate()) {
assertType<number>(val.attribute); // Error
~~~~~~~~~~~~~
!!! error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number'.
!!! error TS2345: Type 'null' is not assignable to type 'number'.
}

153 changes: 153 additions & 0 deletions tests/baselines/reference/typePredicatesInUnion3.symbols
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@@ -0,0 +1,153 @@
=== tests/cases/compiler/typePredicatesInUnion3.ts ===
// A union of function types is considered a type predicate if at least one constituent is a type
// predicate and the other constituents are matching type predicates or functions returning `false`.

type P1 = (x: unknown) => x is string;
>P1 : Symbol(P1, Decl(typePredicatesInUnion3.ts, 0, 0))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 3, 11))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 3, 11))

type P2 = (x: unknown) => x is number;
>P2 : Symbol(P2, Decl(typePredicatesInUnion3.ts, 3, 38))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 4, 11))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 4, 11))

type F1 = (x: unknown) => false;
>F1 : Symbol(F1, Decl(typePredicatesInUnion3.ts, 4, 38))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 6, 11))

type F2 = (x: unknown) => boolean;
>F2 : Symbol(F2, Decl(typePredicatesInUnion3.ts, 6, 32))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 7, 11))

type F3 = (x: unknown) => string;
>F3 : Symbol(F3, Decl(typePredicatesInUnion3.ts, 7, 34))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 8, 11))

function f1(x: unknown, p: P1 | P2) {
>f1 : Symbol(f1, Decl(typePredicatesInUnion3.ts, 8, 33))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 10, 12))
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 10, 23))
>P1 : Symbol(P1, Decl(typePredicatesInUnion3.ts, 0, 0))
>P2 : Symbol(P2, Decl(typePredicatesInUnion3.ts, 3, 38))

if (p(x)) {
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 10, 23))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 10, 12))

x; // string | number
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 10, 12))
}
}

function f2(x: unknown, p: P1 | P2 | F1) {
>f2 : Symbol(f2, Decl(typePredicatesInUnion3.ts, 14, 1))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 16, 12))
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 16, 23))
>P1 : Symbol(P1, Decl(typePredicatesInUnion3.ts, 0, 0))
>P2 : Symbol(P2, Decl(typePredicatesInUnion3.ts, 3, 38))
>F1 : Symbol(F1, Decl(typePredicatesInUnion3.ts, 4, 38))

if (p(x)) {
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 16, 23))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 16, 12))

x; // string | number
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 16, 12))
}
}

function f3(x: unknown, p: P1 | P2 | F2) {
>f3 : Symbol(f3, Decl(typePredicatesInUnion3.ts, 20, 1))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 22, 12))
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 22, 23))
>P1 : Symbol(P1, Decl(typePredicatesInUnion3.ts, 0, 0))
>P2 : Symbol(P2, Decl(typePredicatesInUnion3.ts, 3, 38))
>F2 : Symbol(F2, Decl(typePredicatesInUnion3.ts, 6, 32))

if (p(x)) {
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 22, 23))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 22, 12))

x; // unknown
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 22, 12))
}
}

function f4(x: unknown, p: P1 | P2 | F3) {
>f4 : Symbol(f4, Decl(typePredicatesInUnion3.ts, 26, 1))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 28, 12))
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 28, 23))
>P1 : Symbol(P1, Decl(typePredicatesInUnion3.ts, 0, 0))
>P2 : Symbol(P2, Decl(typePredicatesInUnion3.ts, 3, 38))
>F3 : Symbol(F3, Decl(typePredicatesInUnion3.ts, 7, 34))

if (p(x)) {
>p : Symbol(p, Decl(typePredicatesInUnion3.ts, 28, 23))
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 28, 12))

x; // unknown
>x : Symbol(x, Decl(typePredicatesInUnion3.ts, 28, 12))
}
}

// Repro from #54143

type HasAttribute<T> = T & { attribute: number };
>HasAttribute : Symbol(HasAttribute, Decl(typePredicatesInUnion3.ts, 32, 1))
>T : Symbol(T, Decl(typePredicatesInUnion3.ts, 36, 18))
>T : Symbol(T, Decl(typePredicatesInUnion3.ts, 36, 18))
>attribute : Symbol(attribute, Decl(typePredicatesInUnion3.ts, 36, 28))

class Type1 {
>Type1 : Symbol(Type1, Decl(typePredicatesInUnion3.ts, 36, 49))

attribute: number | null = null;
>attribute : Symbol(Type1.attribute, Decl(typePredicatesInUnion3.ts, 38, 13))

predicate(): this is HasAttribute<Type1> {
>predicate : Symbol(Type1.predicate, Decl(typePredicatesInUnion3.ts, 39, 36))
>HasAttribute : Symbol(HasAttribute, Decl(typePredicatesInUnion3.ts, 32, 1))
>Type1 : Symbol(Type1, Decl(typePredicatesInUnion3.ts, 36, 49))

return true;
}
}

class Type2 {
>Type2 : Symbol(Type2, Decl(typePredicatesInUnion3.ts, 43, 1))

attribute: number | null = null;
>attribute : Symbol(Type2.attribute, Decl(typePredicatesInUnion3.ts, 45, 13))

predicate(): boolean {
>predicate : Symbol(Type2.predicate, Decl(typePredicatesInUnion3.ts, 46, 36))

return true;
}
}

function assertType<T>(_val: T) {
>assertType : Symbol(assertType, Decl(typePredicatesInUnion3.ts, 50, 1))
>T : Symbol(T, Decl(typePredicatesInUnion3.ts, 52, 20))
>_val : Symbol(_val, Decl(typePredicatesInUnion3.ts, 52, 23))
>T : Symbol(T, Decl(typePredicatesInUnion3.ts, 52, 20))
}

declare const val: Type1 | Type2;
>val : Symbol(val, Decl(typePredicatesInUnion3.ts, 55, 13))
>Type1 : Symbol(Type1, Decl(typePredicatesInUnion3.ts, 36, 49))
>Type2 : Symbol(Type2, Decl(typePredicatesInUnion3.ts, 43, 1))

if (val.predicate()) {
>val.predicate : Symbol(predicate, Decl(typePredicatesInUnion3.ts, 39, 36), Decl(typePredicatesInUnion3.ts, 46, 36))
>val : Symbol(val, Decl(typePredicatesInUnion3.ts, 55, 13))
>predicate : Symbol(predicate, Decl(typePredicatesInUnion3.ts, 39, 36), Decl(typePredicatesInUnion3.ts, 46, 36))

assertType<number>(val.attribute); // Error
>assertType : Symbol(assertType, Decl(typePredicatesInUnion3.ts, 50, 1))
>val.attribute : Symbol(attribute, Decl(typePredicatesInUnion3.ts, 38, 13), Decl(typePredicatesInUnion3.ts, 45, 13))
>val : Symbol(val, Decl(typePredicatesInUnion3.ts, 55, 13))
>attribute : Symbol(attribute, Decl(typePredicatesInUnion3.ts, 38, 13), Decl(typePredicatesInUnion3.ts, 45, 13))
}

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