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Fix reachability analysis for 'assert x is T' assertion type predicates #39177

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Fix reachability analysis for 'assert x is T' assertion type predicates #39177

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53a7b6d
Assertions of the form 'assert x is T' shouldn't affect reachability
ahejlsberg Jun 21, 2020
7e13e01
Add regression test
ahejlsberg Jun 21, 2020
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2 changes: 1 addition & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20459,7 +20459,7 @@ namespace ts {
const signature = getEffectsSignature((<FlowCall>flow).node);
if (signature) {
const predicate = getTypePredicateOfSignature(signature);
if (predicate && predicate.kind === TypePredicateKind.AssertsIdentifier) {
if (predicate && predicate.kind === TypePredicateKind.AssertsIdentifier && !predicate.type) {
const predicateArgument = (<FlowCall>flow).node.arguments[predicate.parameterIndex];
if (predicateArgument && isFalseExpression(predicateArgument)) {
return false;
Expand Down
8 changes: 8 additions & 0 deletions tests/baselines/reference/assertionTypePredicates1.errors.txt
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Expand Up @@ -239,4 +239,12 @@ tests/cases/conformance/controlFlow/assertionTypePredicates1.ts(170,5): error TS
thing.good;
}
}

// Repro from #38699

declare function strictEqual<T>(actual: any, expected: T, message?: string | Error): asserts actual is T;

const b = false;
strictEqual(false, b);
let b2 = b;

14 changes: 14 additions & 0 deletions tests/baselines/reference/assertionTypePredicates1.js
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Expand Up @@ -190,6 +190,14 @@ function example1(things: Thing[]) {
thing.good;
}
}

// Repro from #38699

declare function strictEqual<T>(actual: any, expected: T, message?: string | Error): asserts actual is T;

const b = false;
strictEqual(false, b);
let b2 = b;


//// [assertionTypePredicates1.js]
Expand Down Expand Up @@ -374,6 +382,9 @@ function example1(things) {
thing.good;
}
}
var b = false;
strictEqual(false, b);
var b2 = b;


//// [assertionTypePredicates1.d.ts]
Expand Down Expand Up @@ -426,3 +437,6 @@ interface GoodThing {
good: true;
}
declare function example1(things: Thing[]): void;
declare function strictEqual<T>(actual: any, expected: T, message?: string | Error): asserts actual is T;
declare const b = false;
declare let b2: boolean;
24 changes: 24 additions & 0 deletions tests/baselines/reference/assertionTypePredicates1.symbols
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Expand Up @@ -542,3 +542,27 @@ function example1(things: Thing[]) {
}
}

// Repro from #38699

declare function strictEqual<T>(actual: any, expected: T, message?: string | Error): asserts actual is T;
>strictEqual : Symbol(strictEqual, Decl(assertionTypePredicates1.ts, 190, 1))
>T : Symbol(T, Decl(assertionTypePredicates1.ts, 194, 29))
>actual : Symbol(actual, Decl(assertionTypePredicates1.ts, 194, 32))
>expected : Symbol(expected, Decl(assertionTypePredicates1.ts, 194, 44))
>T : Symbol(T, Decl(assertionTypePredicates1.ts, 194, 29))
>message : Symbol(message, Decl(assertionTypePredicates1.ts, 194, 57))
>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
>actual : Symbol(actual, Decl(assertionTypePredicates1.ts, 194, 32))
>T : Symbol(T, Decl(assertionTypePredicates1.ts, 194, 29))

const b = false;
>b : Symbol(b, Decl(assertionTypePredicates1.ts, 196, 5))

strictEqual(false, b);
>strictEqual : Symbol(strictEqual, Decl(assertionTypePredicates1.ts, 190, 1))
>b : Symbol(b, Decl(assertionTypePredicates1.ts, 196, 5))

let b2 = b;
>b2 : Symbol(b2, Decl(assertionTypePredicates1.ts, 198, 3))
>b : Symbol(b, Decl(assertionTypePredicates1.ts, 196, 5))

22 changes: 22 additions & 0 deletions tests/baselines/reference/assertionTypePredicates1.types
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Expand Up @@ -666,3 +666,25 @@ function example1(things: Thing[]) {
}
}

// Repro from #38699

declare function strictEqual<T>(actual: any, expected: T, message?: string | Error): asserts actual is T;
>strictEqual : <T>(actual: any, expected: T, message?: string | Error | undefined) => asserts actual is T
>actual : any
>expected : T
>message : string | Error | undefined

const b = false;
>b : false
>false : false

strictEqual(false, b);
>strictEqual(false, b) : void
>strictEqual : <T>(actual: any, expected: T, message?: string | Error | undefined) => asserts actual is T
>false : false
>b : false

let b2 = b;
>b2 : boolean
>b : false

8 changes: 8 additions & 0 deletions tests/cases/conformance/controlFlow/assertionTypePredicates1.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -193,3 +193,11 @@ function example1(things: Thing[]) {
thing.good;
}
}

// Repro from #38699

declare function strictEqual<T>(actual: any, expected: T, message?: string | Error): asserts actual is T;

const b = false;
strictEqual(false, b);
let b2 = b;