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ahejlsbergahejlsberg
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Merge pull request #27695 from Microsoft/mixedDiscriminantTypes
Allow non-unit types in union discriminants
2 parents c184184 + 6cdba6d commit 9767522

7 files changed

+775
-7
lines changed

‎src/compiler/checker.ts

+15-1
Original file line numberDiff line numberDiff line change
@@ -14233,12 +14233,26 @@ namespace ts {
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return undefined;
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}
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14236+
function isDiscriminantType(type: Type): boolean {
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if (type.flags & TypeFlags.Union) {
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if (type.flags & (TypeFlags.Boolean | TypeFlags.EnumLiteral)) {
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return true;
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}
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let combined = 0;
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for (const t of (<UnionType>type).types) combined |= t.flags;
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if (combined & TypeFlags.Unit && !(combined & TypeFlags.Instantiable)) {
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return true;
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}
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}
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return false;
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}
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function isDiscriminantProperty(type: Type | undefined, name: __String) {
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if (type && type.flags & TypeFlags.Union) {
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const prop = getUnionOrIntersectionProperty(<UnionType>type, name);
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if (prop && getCheckFlags(prop) & CheckFlags.SyntheticProperty) {
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if ((<TransientSymbol>prop).isDiscriminantProperty === undefined) {
14241-
(<TransientSymbol>prop).isDiscriminantProperty = !!((<TransientSymbol>prop).checkFlags & CheckFlags.HasNonUniformType) && isLiteralType(getTypeOfSymbol(prop));
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(<TransientSymbol>prop).isDiscriminantProperty = !!((<TransientSymbol>prop).checkFlags & CheckFlags.HasNonUniformType) && isDiscriminantType(getTypeOfSymbol(prop));
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}
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return !!(<TransientSymbol>prop).isDiscriminantProperty;
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}

‎tests/baselines/reference/discriminatedUnionTypes2.errors.txt

+86
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,86 @@
1+
tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(27,30): error TS2322: Type '{ a: null; b: string; c: number; }' is not assignable to type '{ a: null; b: string; } | { a: string; c: number; }'.
2+
Object literal may only specify known properties, and 'c' does not exist in type '{ a: null; b: string; }'.
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tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(32,11): error TS2339: Property 'b' does not exist on type '{ a: 0; b: string; } | { a: T; c: number; }'.
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Property 'b' does not exist on type '{ a: T; c: number; }'.
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==== tests/cases/conformance/types/union/discriminatedUnionTypes2.ts (2 errors) ====
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function f10(x : { kind: false, a: string } | { kind: true, b: string } | { kind: string, c: string }) {
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if (x.kind === false) {
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x.a;
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}
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else if (x.kind === true) {
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x.b;
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}
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else {
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x.c;
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}
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}
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function f11(x : { kind: false, a: string } | { kind: true, b: string } | { kind: string, c: string }) {
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switch (x.kind) {
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case false:
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x.a;
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break;
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case true:
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x.b;
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break;
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default:
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x.c;
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}
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}
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function f13(x: { a: null; b: string } | { a: string, c: number }) {
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x = { a: null, b: "foo", c: 4}; // Error
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~~~~
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!!! error TS2322: Type '{ a: null; b: string; c: number; }' is not assignable to type '{ a: null; b: string; } | { a: string; c: number; }'.
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!!! error TS2322: Object literal may only specify known properties, and 'c' does not exist in type '{ a: null; b: string; }'.
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}
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function f14<T>(x: { a: 0; b: string } | { a: T, c: number }) {
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if (x.a === 0) {
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x.b; // Error
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~
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!!! error TS2339: Property 'b' does not exist on type '{ a: 0; b: string; } | { a: T; c: number; }'.
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!!! error TS2339: Property 'b' does not exist on type '{ a: T; c: number; }'.
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}
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}
48+
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type Result<T> = { error?: undefined, value: T } | { error: Error };
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function f15(x: Result<number>) {
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if (!x.error) {
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x.value;
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}
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else {
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x.error.message;
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}
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}
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f15({ value: 10 });
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f15({ error: new Error("boom") });
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// Repro from #24193
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interface WithError {
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error: Error
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data: null
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}
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interface WithoutError<Data> {
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error: null
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data: Data
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}
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type DataCarrier<Data> = WithError | WithoutError<Data>
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function f20<Data>(carrier: DataCarrier<Data>) {
78+
if (carrier.error === null) {
79+
const error: null = carrier.error
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const data: Data = carrier.data
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} else {
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const error: Error = carrier.error
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const data: null = carrier.data
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}
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}
86+

‎tests/baselines/reference/discriminatedUnionTypes2.js

+128
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,128 @@
1+
//// [discriminatedUnionTypes2.ts]
2+
function f10(x : { kind: false, a: string } | { kind: true, b: string } | { kind: string, c: string }) {
3+
if (x.kind === false) {
4+
x.a;
5+
}
6+
else if (x.kind === true) {
7+
x.b;
8+
}
9+
else {
10+
x.c;
11+
}
12+
}
13+
14+
function f11(x : { kind: false, a: string } | { kind: true, b: string } | { kind: string, c: string }) {
15+
switch (x.kind) {
16+
case false:
17+
x.a;
18+
break;
19+
case true:
20+
x.b;
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break;
22+
default:
23+
x.c;
24+
}
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}
26+
27+
function f13(x: { a: null; b: string } | { a: string, c: number }) {
28+
x = { a: null, b: "foo", c: 4}; // Error
29+
}
30+
31+
function f14<T>(x: { a: 0; b: string } | { a: T, c: number }) {
32+
if (x.a === 0) {
33+
x.b; // Error
34+
}
35+
}
36+
37+
type Result<T> = { error?: undefined, value: T } | { error: Error };
38+
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function f15(x: Result<number>) {
40+
if (!x.error) {
41+
x.value;
42+
}
43+
else {
44+
x.error.message;
45+
}
46+
}
47+
48+
f15({ value: 10 });
49+
f15({ error: new Error("boom") });
50+
51+
// Repro from #24193
52+
53+
interface WithError {
54+
error: Error
55+
data: null
56+
}
57+
58+
interface WithoutError<Data> {
59+
error: null
60+
data: Data
61+
}
62+
63+
type DataCarrier<Data> = WithError | WithoutError<Data>
64+
65+
function f20<Data>(carrier: DataCarrier<Data>) {
66+
if (carrier.error === null) {
67+
const error: null = carrier.error
68+
const data: Data = carrier.data
69+
} else {
70+
const error: Error = carrier.error
71+
const data: null = carrier.data
72+
}
73+
}
74+
75+
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//// [discriminatedUnionTypes2.js]
77+
"use strict";
78+
function f10(x) {
79+
if (x.kind === false) {
80+
x.a;
81+
}
82+
else if (x.kind === true) {
83+
x.b;
84+
}
85+
else {
86+
x.c;
87+
}
88+
}
89+
function f11(x) {
90+
switch (x.kind) {
91+
case false:
92+
x.a;
93+
break;
94+
case true:
95+
x.b;
96+
break;
97+
default:
98+
x.c;
99+
}
100+
}
101+
function f13(x) {
102+
x = { a: null, b: "foo", c: 4 }; // Error
103+
}
104+
function f14(x) {
105+
if (x.a === 0) {
106+
x.b; // Error
107+
}
108+
}
109+
function f15(x) {
110+
if (!x.error) {
111+
x.value;
112+
}
113+
else {
114+
x.error.message;
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}
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}
117+
f15({ value: 10 });
118+
f15({ error: new Error("boom") });
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function f20(carrier) {
120+
if (carrier.error === null) {
121+
var error = carrier.error;
122+
var data = carrier.data;
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}
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else {
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var error = carrier.error;
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var data = carrier.data;
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}
128+
}

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