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Fix: Make discriminant property selection order-independent in unions (#62512) #62516

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Fix: Make discriminant property selection order-independent in unions (#62512) #62516

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61 changes: 61 additions & 0 deletions tests/baselines/reference/discriminantOrderIndependence.js
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//// [tests/cases/compiler/discriminantOrderIndependence.ts] ////

//// [discriminantOrderIndependence.ts]
interface A {
subType: "b";
type: "a";
}

declare let order1:
| { type: "1" }
| A
| { type: "2" }
| { type: "3" }
| undefined;

// Should NOT error: 'order1' is possibly 'undefined' after the guard
if (order1 && order1.type === "a") {
order1.type; // Should be OK
}

interface B {
subType: "b";
type: "a";
}

declare let order2:
| { type: "1" }
| { type: "2" }
| { type: "3" }
| B
| undefined;

// Should NOT error: 'order2' is possibly 'undefined' after the guard
if (order2 && order2.type === "a") {
order2.type; // Should be OK
}

// Also test with !. type assertion
if (order1 && order1.type === "a") {
order1.type; // Should be OK
}
if (order2 && order2.type === "a") {
order2.type; // Should be OK
}

//// [discriminantOrderIndependence.js]
// Should NOT error: 'order1' is possibly 'undefined' after the guard
if (order1 && order1.type === "a") {
order1.type; // Should be OK
}
// Should NOT error: 'order2' is possibly 'undefined' after the guard
if (order2 && order2.type === "a") {
order2.type; // Should be OK
}
// Also test with !. type assertion
if (order1 && order1.type === "a") {
order1.type; // Should be OK
}
if (order2 && order2.type === "a") {
order2.type; // Should be OK
}
106 changes: 106 additions & 0 deletions tests/baselines/reference/discriminantOrderIndependence.symbols
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//// [tests/cases/compiler/discriminantOrderIndependence.ts] ////

=== discriminantOrderIndependence.ts ===
interface A {
>A : Symbol(A, Decl(discriminantOrderIndependence.ts, 0, 0))

subType: "b";
>subType : Symbol(A.subType, Decl(discriminantOrderIndependence.ts, 0, 13))

type: "a";
>type : Symbol(A.type, Decl(discriminantOrderIndependence.ts, 1, 17))
}

declare let order1:
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))

| { type: "1" }
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 6, 7))

| A
>A : Symbol(A, Decl(discriminantOrderIndependence.ts, 0, 0))

| { type: "2" }
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 8, 7))

| { type: "3" }
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 9, 7))

| undefined;

// Should NOT error: 'order1' is possibly 'undefined' after the guard
if (order1 && order1.type === "a") {
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))
>order1.type : Symbol(type, Decl(discriminantOrderIndependence.ts, 1, 17), Decl(discriminantOrderIndependence.ts, 6, 7), Decl(discriminantOrderIndependence.ts, 8, 7), Decl(discriminantOrderIndependence.ts, 9, 7))
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 1, 17), Decl(discriminantOrderIndependence.ts, 6, 7), Decl(discriminantOrderIndependence.ts, 8, 7), Decl(discriminantOrderIndependence.ts, 9, 7))

order1.type; // Should be OK
>order1.type : Symbol(A.type, Decl(discriminantOrderIndependence.ts, 1, 17))
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))
>type : Symbol(A.type, Decl(discriminantOrderIndependence.ts, 1, 17))
}

interface B {
>B : Symbol(B, Decl(discriminantOrderIndependence.ts, 15, 1))

subType: "b";
>subType : Symbol(B.subType, Decl(discriminantOrderIndependence.ts, 17, 13))

type: "a";
>type : Symbol(B.type, Decl(discriminantOrderIndependence.ts, 18, 17))
}

declare let order2:
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))

| { type: "1" }
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 23, 7))

| { type: "2" }
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 24, 7))

| { type: "3" }
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 25, 7))

| B
>B : Symbol(B, Decl(discriminantOrderIndependence.ts, 15, 1))

| undefined;

// Should NOT error: 'order2' is possibly 'undefined' after the guard
if (order2 && order2.type === "a") {
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))
>order2.type : Symbol(type, Decl(discriminantOrderIndependence.ts, 18, 17), Decl(discriminantOrderIndependence.ts, 23, 7), Decl(discriminantOrderIndependence.ts, 24, 7), Decl(discriminantOrderIndependence.ts, 25, 7))
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 18, 17), Decl(discriminantOrderIndependence.ts, 23, 7), Decl(discriminantOrderIndependence.ts, 24, 7), Decl(discriminantOrderIndependence.ts, 25, 7))

order2.type; // Should be OK
>order2.type : Symbol(B.type, Decl(discriminantOrderIndependence.ts, 18, 17))
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))
>type : Symbol(B.type, Decl(discriminantOrderIndependence.ts, 18, 17))
}

// Also test with !. type assertion
if (order1 && order1.type === "a") {
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))
>order1.type : Symbol(type, Decl(discriminantOrderIndependence.ts, 1, 17), Decl(discriminantOrderIndependence.ts, 6, 7), Decl(discriminantOrderIndependence.ts, 8, 7), Decl(discriminantOrderIndependence.ts, 9, 7))
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 1, 17), Decl(discriminantOrderIndependence.ts, 6, 7), Decl(discriminantOrderIndependence.ts, 8, 7), Decl(discriminantOrderIndependence.ts, 9, 7))

order1.type; // Should be OK
>order1.type : Symbol(A.type, Decl(discriminantOrderIndependence.ts, 1, 17))
>order1 : Symbol(order1, Decl(discriminantOrderIndependence.ts, 5, 11))
>type : Symbol(A.type, Decl(discriminantOrderIndependence.ts, 1, 17))
}
if (order2 && order2.type === "a") {
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))
>order2.type : Symbol(type, Decl(discriminantOrderIndependence.ts, 18, 17), Decl(discriminantOrderIndependence.ts, 23, 7), Decl(discriminantOrderIndependence.ts, 24, 7), Decl(discriminantOrderIndependence.ts, 25, 7))
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))
>type : Symbol(type, Decl(discriminantOrderIndependence.ts, 18, 17), Decl(discriminantOrderIndependence.ts, 23, 7), Decl(discriminantOrderIndependence.ts, 24, 7), Decl(discriminantOrderIndependence.ts, 25, 7))

order2.type; // Should be OK
>order2.type : Symbol(B.type, Decl(discriminantOrderIndependence.ts, 18, 17))
>order2 : Symbol(order2, Decl(discriminantOrderIndependence.ts, 22, 11))
>type : Symbol(B.type, Decl(discriminantOrderIndependence.ts, 18, 17))
}
162 changes: 162 additions & 0 deletions tests/baselines/reference/discriminantOrderIndependence.types
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//// [tests/cases/compiler/discriminantOrderIndependence.ts] ////

=== discriminantOrderIndependence.ts ===
interface A {
subType: "b";
>subType : "b"
> : ^^^

type: "a";
>type : "a"
> : ^^^
}

declare let order1:
>order1 : A | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^

| { type: "1" }
>type : "1"
> : ^^^

| A
| { type: "2" }
>type : "2"
> : ^^^

| { type: "3" }
>type : "3"
> : ^^^

| undefined;

// Should NOT error: 'order1' is possibly 'undefined' after the guard
if (order1 && order1.type === "a") {
>order1 && order1.type === "a" : boolean
> : ^^^^^^^
>order1 : A | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>order1.type === "a" : boolean
> : ^^^^^^^
>order1.type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>order1 : A | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>"a" : "a"
> : ^^^

order1.type; // Should be OK
>order1.type : "a"
> : ^^^
>order1 : A
> : ^
>type : "a"
> : ^^^
}

interface B {
subType: "b";
>subType : "b"
> : ^^^

type: "a";
>type : "a"
> : ^^^
}

declare let order2:
>order2 : B | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^

| { type: "1" }
>type : "1"
> : ^^^

| { type: "2" }
>type : "2"
> : ^^^

| { type: "3" }
>type : "3"
> : ^^^

| B
| undefined;

// Should NOT error: 'order2' is possibly 'undefined' after the guard
if (order2 && order2.type === "a") {
>order2 && order2.type === "a" : boolean
> : ^^^^^^^
>order2 : B | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>order2.type === "a" : boolean
> : ^^^^^^^
>order2.type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>order2 : B | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>"a" : "a"
> : ^^^

order2.type; // Should be OK
>order2.type : "a"
> : ^^^
>order2 : B
> : ^
>type : "a"
> : ^^^
}

// Also test with !. type assertion
if (order1 && order1.type === "a") {
>order1 && order1.type === "a" : boolean
> : ^^^^^^^
>order1 : A | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>order1.type === "a" : boolean
> : ^^^^^^^
>order1.type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>order1 : A | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>"a" : "a"
> : ^^^

order1.type; // Should be OK
>order1.type : "a"
> : ^^^
>order1 : A
> : ^
>type : "a"
> : ^^^
}
if (order2 && order2.type === "a") {
>order2 && order2.type === "a" : boolean
> : ^^^^^^^
>order2 : B | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>order2.type === "a" : boolean
> : ^^^^^^^
>order2.type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>order2 : B | { type: "1"; } | { type: "2"; } | { type: "3"; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^
>type : "a" | "1" | "2" | "3"
> : ^^^^^^^^^^^^^^^^^^^^^
>"a" : "a"
> : ^^^

order2.type; // Should be OK
>order2.type : "a"
> : ^^^
>order2 : B
> : ^
>type : "a"
> : ^^^
}
41 changes: 41 additions & 0 deletions tests/cases/compiler/discriminantOrderIndependence.ts
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interface A {
subType: "b";
type: "a";
}

declare let order1:
| { type: "1" }
| A
| { type: "2" }
| { type: "3" }
| undefined;

// Should NOT error: 'order1' is possibly 'undefined' after the guard
if (order1 && order1.type === "a") {
order1.type; // Should be OK
}

interface B {
subType: "b";
type: "a";
}

declare let order2:
| { type: "1" }
| { type: "2" }
| { type: "3" }
| B
| undefined;

// Should NOT error: 'order2' is possibly 'undefined' after the guard
if (order2 && order2.type === "a") {
order2.type; // Should be OK
}

// Also test with !. type assertion
if (order1 && order1.type === "a") {
order1.type; // Should be OK
}
if (order2 && order2.type === "a") {
order2.type; // Should be OK
}
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