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jack-williamsjack-williams
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Add narrowing for unknown with strict equal
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5 files changed

+408
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lines changed

5 files changed

+408
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lines changed

‎src/compiler/checker.ts

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Original file line numberDiff line numberDiff line change
@@ -14920,6 +14920,9 @@ namespace ts {
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assumeTrue = !assumeTrue;
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}
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const valueType = getTypeOfExpression(value);
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if ((type.flags & TypeFlags.Unknown) && (operator === SyntaxKind.EqualsEqualsEqualsToken) && (valueType.flags & TypeFlags.Unit)) {
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return assumeTrue ? valueType : type;
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}
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if (valueType.flags & TypeFlags.Nullable) {
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if (!strictNullChecks) {
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return type;

‎tests/baselines/reference/unknownType2.js

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//// [unknownType2.ts]
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type isUnknown<T> = unknown extends T ? true : false;
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type isTrue<T extends true> = T;
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type SomeResponse = 'yes' | 'no' | 'idk';
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let validate: (x: unknown) => SomeResponse = x => (x === 'yes' || x === 'no') ? x : 'idk'; // No error
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const u: unknown = undefined;
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declare const symb: unique symbol;
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if (u === 5) {
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const y = u.toString(10);
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}
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if (u === true || u === false) {
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const someBool: boolean = u;
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}
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if (u === undefined) {
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const undef: undefined = u;
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}
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if (u === null) {
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const someNull: null = u;
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}
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if(u === symb) {
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const symbolAlias: typeof symb = u;
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}
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if (!(u === 42)) {
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u // u should still be `unknown` here
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}
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if (u !== 42) {
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type A = isTrue<isUnknown<typeof u>>
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}
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if (u == 42) {
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type B = isTrue<isUnknown<typeof u>>
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}
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if (u == true) {
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type C = isTrue<isUnknown<typeof u>>
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}
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if (u == Object) {
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type D = isTrue<isUnknown<typeof u>>
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}
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//// [unknownType2.js]
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"use strict";
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var validate = function (x) { return (x === 'yes' || x === 'no') ? x : 'idk'; }; // No error
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var u = undefined;
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if (u === 5) {
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var y = u.toString(10);
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}
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if (u === true || u === false) {
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var someBool = u;
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}
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if (u === undefined) {
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var undef = u;
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}
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if (u === null) {
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var someNull = u;
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}
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if (u === symb) {
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var symbolAlias = u;
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}
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if (!(u === 42)) {
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u; // u should still be `unknown` here
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}
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if (u !== 42) {
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}
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if (u == 42) {
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}
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if (u == true) {
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}
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if (u == Object) {
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}

‎tests/baselines/reference/unknownType2.symbols

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=== tests/cases/conformance/types/unknown/unknownType2.ts ===
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type isUnknown<T> = unknown extends T ? true : false;
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>isUnknown : Symbol(isUnknown, Decl(unknownType2.ts, 0, 0))
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>T : Symbol(T, Decl(unknownType2.ts, 0, 15))
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>T : Symbol(T, Decl(unknownType2.ts, 0, 15))
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type isTrue<T extends true> = T;
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>isTrue : Symbol(isTrue, Decl(unknownType2.ts, 0, 53))
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>T : Symbol(T, Decl(unknownType2.ts, 1, 12))
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>T : Symbol(T, Decl(unknownType2.ts, 1, 12))
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type SomeResponse = 'yes' | 'no' | 'idk';
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>SomeResponse : Symbol(SomeResponse, Decl(unknownType2.ts, 1, 32))
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let validate: (x: unknown) => SomeResponse = x => (x === 'yes' || x === 'no') ? x : 'idk'; // No error
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>validate : Symbol(validate, Decl(unknownType2.ts, 4, 3))
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>x : Symbol(x, Decl(unknownType2.ts, 4, 15))
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>SomeResponse : Symbol(SomeResponse, Decl(unknownType2.ts, 1, 32))
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>x : Symbol(x, Decl(unknownType2.ts, 4, 44))
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>x : Symbol(x, Decl(unknownType2.ts, 4, 44))
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>x : Symbol(x, Decl(unknownType2.ts, 4, 44))
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>x : Symbol(x, Decl(unknownType2.ts, 4, 44))
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const u: unknown = undefined;
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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>undefined : Symbol(undefined)
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declare const symb: unique symbol;
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>symb : Symbol(symb, Decl(unknownType2.ts, 8, 13))
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if (u === 5) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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const y = u.toString(10);
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>y : Symbol(y, Decl(unknownType2.ts, 11, 9))
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>u.toString : Symbol(Number.toString, Decl(lib.es5.d.ts, --, --))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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>toString : Symbol(Number.toString, Decl(lib.es5.d.ts, --, --))
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}
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if (u === true || u === false) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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const someBool: boolean = u;
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>someBool : Symbol(someBool, Decl(unknownType2.ts, 15, 9))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (u === undefined) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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>undefined : Symbol(undefined)
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const undef: undefined = u;
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>undef : Symbol(undef, Decl(unknownType2.ts, 19, 9))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (u === null) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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const someNull: null = u;
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>someNull : Symbol(someNull, Decl(unknownType2.ts, 23, 9))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if(u === symb) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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>symb : Symbol(symb, Decl(unknownType2.ts, 8, 13))
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const symbolAlias: typeof symb = u;
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>symbolAlias : Symbol(symbolAlias, Decl(unknownType2.ts, 27, 9))
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>symb : Symbol(symb, Decl(unknownType2.ts, 8, 13))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (!(u === 42)) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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u // u should still be `unknown` here
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (u !== 42) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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type A = isTrue<isUnknown<typeof u>>
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>A : Symbol(A, Decl(unknownType2.ts, 34, 15))
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>isTrue : Symbol(isTrue, Decl(unknownType2.ts, 0, 53))
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>isUnknown : Symbol(isUnknown, Decl(unknownType2.ts, 0, 0))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (u == 42) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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type B = isTrue<isUnknown<typeof u>>
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>B : Symbol(B, Decl(unknownType2.ts, 38, 14))
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>isTrue : Symbol(isTrue, Decl(unknownType2.ts, 0, 53))
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>isUnknown : Symbol(isUnknown, Decl(unknownType2.ts, 0, 0))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (u == true) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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type C = isTrue<isUnknown<typeof u>>
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>C : Symbol(C, Decl(unknownType2.ts, 42, 16))
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>isTrue : Symbol(isTrue, Decl(unknownType2.ts, 0, 53))
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>isUnknown : Symbol(isUnknown, Decl(unknownType2.ts, 0, 0))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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if (u == Object) {
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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type D = isTrue<isUnknown<typeof u>>
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>D : Symbol(D, Decl(unknownType2.ts, 46, 18))
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>isTrue : Symbol(isTrue, Decl(unknownType2.ts, 0, 53))
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>isUnknown : Symbol(isUnknown, Decl(unknownType2.ts, 0, 0))
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>u : Symbol(u, Decl(unknownType2.ts, 6, 5))
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}
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‎tests/baselines/reference/unknownType2.types

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=== tests/cases/conformance/types/unknown/unknownType2.ts ===
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type isUnknown<T> = unknown extends T ? true : false;
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>isUnknown : isUnknown<T>
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>true : true
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>false : false
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type isTrue<T extends true> = T;
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>isTrue : T
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>true : true
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type SomeResponse = 'yes' | 'no' | 'idk';
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>SomeResponse : SomeResponse
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let validate: (x: unknown) => SomeResponse = x => (x === 'yes' || x === 'no') ? x : 'idk'; // No error
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>validate : (x: unknown) => SomeResponse
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>x : unknown
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>x => (x === 'yes' || x === 'no') ? x : 'idk' : (x: unknown) => "yes" | "no" | "idk"
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>x : unknown
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>(x === 'yes' || x === 'no') ? x : 'idk' : SomeResponse
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>(x === 'yes' || x === 'no') : boolean
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>x === 'yes' || x === 'no' : boolean
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>x === 'yes' : boolean
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>x : unknown
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>'yes' : "yes"
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>x === 'no' : boolean
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>x : unknown
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>'no' : "no"
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>x : "yes" | "no"
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>'idk' : "idk"
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const u: unknown = undefined;
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>u : unknown
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>undefined : undefined
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declare const symb: unique symbol;
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>symb : unique symbol
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if (u === 5) {
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>u === 5 : boolean
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>u : unknown
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>5 : 5
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const y = u.toString(10);
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>y : string
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>u.toString(10) : string
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>u.toString : (radix?: number | undefined) => string
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>u : 5
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>toString : (radix?: number | undefined) => string
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>10 : 10
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}
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if (u === true || u === false) {
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>u === true || u === false : boolean
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>u === true : boolean
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>u : unknown
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>true : true
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>u === false : boolean
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>u : unknown
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>false : false
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const someBool: boolean = u;
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>someBool : boolean
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>u : boolean
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}
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if (u === undefined) {
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>u === undefined : boolean
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>u : unknown
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>undefined : undefined
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const undef: undefined = u;
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>undef : undefined
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>u : undefined
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}
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if (u === null) {
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>u === null : boolean
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>u : unknown
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>null : null
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const someNull: null = u;
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>someNull : null
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>null : null
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>u : null
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}
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if(u === symb) {
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>u === symb : boolean
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>u : unknown
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>symb : unique symbol
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const symbolAlias: typeof symb = u;
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>symbolAlias : unique symbol
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>symb : unique symbol
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>u : unique symbol
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}
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if (!(u === 42)) {
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>!(u === 42) : boolean
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>(u === 42) : boolean
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>u === 42 : boolean
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>u : unknown
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>42 : 42
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u // u should still be `unknown` here
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>u : unknown
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}
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if (u !== 42) {
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>u !== 42 : boolean
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>u : unknown
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>42 : 42
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type A = isTrue<isUnknown<typeof u>>
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>A : true
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>u : unknown
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}
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if (u == 42) {
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>u == 42 : boolean
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>u : unknown
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>42 : 42
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type B = isTrue<isUnknown<typeof u>>
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>B : true
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>u : unknown
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}
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if (u == true) {
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>u == true : boolean
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>u : unknown
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>true : true
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type C = isTrue<isUnknown<typeof u>>
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>C : true
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>u : unknown
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}
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if (u == Object) {
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>u == Object : boolean
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>u : unknown
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>Object : ObjectConstructor
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type D = isTrue<isUnknown<typeof u>>
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>D : true
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>u : unknown
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}
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