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Fix #33448 - Filter discriminants of type never #33498

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Fix #33448 - Filter discriminants of type never #33498

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9 changes: 8 additions & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17363,7 +17363,14 @@ namespace ts {
}
const propType = getTypeOfPropertyOfType(type, propName);
const narrowedPropType = propType && narrowType(propType);
return propType === narrowedPropType ? type : filterType(type, t => isTypeComparableTo(getTypeOfPropertyOrIndexSignature(t, propName), narrowedPropType!));
if (propType === narrowedPropType) {
return type;
}
const isPropertyDiscriminated = (t: Type) => {
const constituentPropType = getTypeOfPropertyOrIndexSignature(t, propName);
return (constituentPropType.flags & TypeFlags.Never) === 0 && isTypeComparableTo(constituentPropType, narrowedPropType!);
};
return filterType(type, isPropertyDiscriminated);
}

function narrowTypeByTruthiness(type: Type, expr: Expression, assumeTrue: boolean): Type {
Expand Down
23 changes: 23 additions & 0 deletions tests/baselines/reference/discriminatedUnionTypes2.errors.txt
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Expand Up @@ -105,4 +105,27 @@ tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(32,11): error TS
foo;
}
}

// Repro from #33448

type a = {
type: 'a',
data: string
}
type b = {
type: 'b',
name: string
}
type c = {
type: 'c',
other: string
}
type abc = a | b | c;
function f(problem: abc & (b | c)) {
if (problem.type === 'b') {
console.log(problem.name);
} else {
console.log(problem.other);
}
}

31 changes: 31 additions & 0 deletions tests/baselines/reference/discriminatedUnionTypes2.js
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Expand Up @@ -93,6 +93,29 @@ function f31(foo: Foo) {
foo;
}
}

// Repro from #33448

type a = {
type: 'a',
data: string
}
type b = {
type: 'b',
name: string
}
type c = {
type: 'c',
other: string
}
type abc = a | b | c;
function f(problem: abc & (b | c)) {
if (problem.type === 'b') {
console.log(problem.name);
} else {
console.log(problem.other);
}
}


//// [discriminatedUnionTypes2.js]
Expand Down Expand Up @@ -164,3 +187,11 @@ function f31(foo) {
foo;
}
}
function f(problem) {
if (problem.type === 'b') {
console.log(problem.name);
}
else {
console.log(problem.other);
}
}
66 changes: 66 additions & 0 deletions tests/baselines/reference/discriminatedUnionTypes2.symbols
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Expand Up @@ -273,3 +273,69 @@ function f31(foo: Foo) {
}
}

// Repro from #33448

type a = {
>a : Symbol(a, Decl(discriminatedUnionTypes2.ts, 93, 1))

type: 'a',
>type : Symbol(type, Decl(discriminatedUnionTypes2.ts, 97, 10))

data: string
>data : Symbol(data, Decl(discriminatedUnionTypes2.ts, 98, 14))
}
type b = {
>b : Symbol(b, Decl(discriminatedUnionTypes2.ts, 100, 1))

type: 'b',
>type : Symbol(type, Decl(discriminatedUnionTypes2.ts, 101, 10))

name: string
>name : Symbol(name, Decl(discriminatedUnionTypes2.ts, 102, 14))
}
type c = {
>c : Symbol(c, Decl(discriminatedUnionTypes2.ts, 104, 1))

type: 'c',
>type : Symbol(type, Decl(discriminatedUnionTypes2.ts, 105, 10))

other: string
>other : Symbol(other, Decl(discriminatedUnionTypes2.ts, 106, 14))
}
type abc = a | b | c;
>abc : Symbol(abc, Decl(discriminatedUnionTypes2.ts, 108, 1))
>a : Symbol(a, Decl(discriminatedUnionTypes2.ts, 93, 1))
>b : Symbol(b, Decl(discriminatedUnionTypes2.ts, 100, 1))
>c : Symbol(c, Decl(discriminatedUnionTypes2.ts, 104, 1))

function f(problem: abc & (b | c)) {
>f : Symbol(f, Decl(discriminatedUnionTypes2.ts, 109, 21))
>problem : Symbol(problem, Decl(discriminatedUnionTypes2.ts, 110, 11))
>abc : Symbol(abc, Decl(discriminatedUnionTypes2.ts, 108, 1))
>b : Symbol(b, Decl(discriminatedUnionTypes2.ts, 100, 1))
>c : Symbol(c, Decl(discriminatedUnionTypes2.ts, 104, 1))

if (problem.type === 'b') {
>problem.type : Symbol(type, Decl(discriminatedUnionTypes2.ts, 101, 10), Decl(discriminatedUnionTypes2.ts, 105, 10), Decl(discriminatedUnionTypes2.ts, 97, 10), Decl(discriminatedUnionTypes2.ts, 101, 10), Decl(discriminatedUnionTypes2.ts, 97, 10) ... and 5 more)
>problem : Symbol(problem, Decl(discriminatedUnionTypes2.ts, 110, 11))
>type : Symbol(type, Decl(discriminatedUnionTypes2.ts, 101, 10), Decl(discriminatedUnionTypes2.ts, 105, 10), Decl(discriminatedUnionTypes2.ts, 97, 10), Decl(discriminatedUnionTypes2.ts, 101, 10), Decl(discriminatedUnionTypes2.ts, 97, 10) ... and 5 more)

console.log(problem.name);
>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
>problem.name : Symbol(name, Decl(discriminatedUnionTypes2.ts, 102, 14))
>problem : Symbol(problem, Decl(discriminatedUnionTypes2.ts, 110, 11))
>name : Symbol(name, Decl(discriminatedUnionTypes2.ts, 102, 14))

} else {
console.log(problem.other);
>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
>problem.other : Symbol(other, Decl(discriminatedUnionTypes2.ts, 106, 14))
>problem : Symbol(problem, Decl(discriminatedUnionTypes2.ts, 110, 11))
>other : Symbol(other, Decl(discriminatedUnionTypes2.ts, 106, 14))
}
}

64 changes: 64 additions & 0 deletions tests/baselines/reference/discriminatedUnionTypes2.types
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Expand Up @@ -289,3 +289,67 @@ function f31(foo: Foo) {
}
}

// Repro from #33448

type a = {
>a : a

type: 'a',
>type : "a"

data: string
>data : string
}
type b = {
>b : b

type: 'b',
>type : "b"

name: string
>name : string
}
type c = {
>c : c

type: 'c',
>type : "c"

other: string
>other : string
}
type abc = a | b | c;
>abc : abc

function f(problem: abc & (b | c)) {
>f : (problem: b | c | (a & b) | (a & c) | (b & c) | (c & b)) => void
>problem : b | c | (a & b) | (a & c) | (b & c) | (c & b)

if (problem.type === 'b') {
>problem.type === 'b' : boolean
>problem.type : "b" | "c"
>problem : b | c | (a & b) | (a & c) | (b & c) | (c & b)
>type : "b" | "c"
>'b' : "b"

console.log(problem.name);
>console.log(problem.name) : void
>console.log : (message?: any, ...optionalParams: any[]) => void
>console : Console
>log : (message?: any, ...optionalParams: any[]) => void
>problem.name : string
>problem : b
>name : string

} else {
console.log(problem.other);
>console.log(problem.other) : void
>console.log : (message?: any, ...optionalParams: any[]) => void
>console : Console
>log : (message?: any, ...optionalParams: any[]) => void
>problem.other : string
>problem : c
>other : string
}
}

23 changes: 23 additions & 0 deletions tests/cases/conformance/types/union/discriminatedUnionTypes2.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -94,3 +94,26 @@ function f31(foo: Foo) {
foo;
}
}

// Repro from #33448

type a = {
type: 'a',
data: string
}
type b = {
type: 'b',
name: string
}
type c = {
type: 'c',
other: string
}
type abc = a | b | c;
function f(problem: abc & (b | c)) {
if (problem.type === 'b') {
console.log(problem.name);
} else {
console.log(problem.other);
}
}