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Require at least a single match when defining discriminable properties #53654

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2f75e38
Do not consider empty literals as values
Apr 3, 2023
424bda8
Second attempt
Apr 4, 2023
86295fb
Include test for non empty literal
Apr 4, 2023
b267256
Move target type calculation inside if
Apr 7, 2023
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9 changes: 3 additions & 6 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22627,12 +22627,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
let i = 0;
for (const type of target.types) {
const targetType = getTypeOfPropertyOfType(type, propertyName);
if (targetType && related(getDiscriminatingType(), targetType)) {
discriminable[i] = discriminable[i] === undefined ? true : discriminable[i];
}
else {
discriminable[i] = false;
if (discriminable[i] === undefined) {
const targetType = getTypeOfPropertyOfType(type, propertyName);
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@MariaSolOs MariaSolOs Apr 4, 2023 •
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To explain this change: This line says that "discriminated types stop at 'true'", but the code is overwriting a potentially true discriminable[i] to false if one of the union variants has a property with a type that's unrelated to the target type (which is what's happening when the property's value is an incomplete string literal).

discriminable[i] = !!(targetType && related(getDiscriminatingType(), targetType));
}
i++;
}
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8 changes: 0 additions & 8 deletions tests/baselines/reference/assignmentCompatWithDiscriminatedUnion.errors.txt
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Expand Up @@ -6,10 +6,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(58,5): error TS2322: Type 'S' is not assignable to type 'T'.
Property 'c' is missing in type 'S' but required in type '{ a: 2; b: 4 | 3; c: string; }'.
tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(82,5): error TS2322: Type 'S' is not assignable to type 'T'.
Type 'S' is not assignable to type '{ a: N; b: N; c: 2; }'.
Types of property 'c' are incompatible.
Type 'N' is not assignable to type '2'.
Type '0' is not assignable to type '2'.
Comment on lines -9 to -12
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I'm not a fan of these errors not being included anymore and I'll try to keep them, but IMO the diagnostic changes in the other files do make sense.

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@MariaSolOs MariaSolOs Apr 6, 2023 •
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@DanielRosenwasser @ahejlsberg Wait I think that those errors are a bug (?). The example says that s should be assignable to t (and if you look at it, it is), but it errors because of the number of combinations being too complex. The diagnostics are incorrect, and so I actually prefer them going away.



==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts (3 errors) ====
Expand Down Expand Up @@ -107,10 +103,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
t = s;
~
!!! error TS2322: Type 'S' is not assignable to type 'T'.
!!! error TS2322: Type 'S' is not assignable to type '{ a: N; b: N; c: 2; }'.
!!! error TS2322: Types of property 'c' are incompatible.
!!! error TS2322: Type 'N' is not assignable to type '2'.
!!! error TS2322: Type '0' is not assignable to type '2'.
}

// https://github.com/Microsoft/TypeScript/issues/14865
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8 changes: 4 additions & 4 deletions tests/baselines/reference/excessPropertyCheckWithMultipleDiscriminants.errors.txt
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@@ -1,7 +1,7 @@
tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(30,5): error TS2322: Type '{ type: "number"; value: number; multipleOf: number; format: string; }' is not assignable to type 'Primitive'.
Object literal may only specify known properties, and 'multipleOf' does not exist in type 'Float'.
tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(41,5): error TS2322: Type '{ p1: "left"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
Object literal may only specify known properties, and 'p3' does not exist in type '{ p1: "left"; p2: boolean; }'.
tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(42,5): error TS2322: Type '{ p1: "left"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
Object literal may only specify known properties, and 'p4' does not exist in type '{ p1: "left"; p2: true; p3: number; } | { p1: "left"; p2: boolean; }'.
tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(50,5): error TS2322: Type '{ p1: "left"; p2: true; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
Object literal may only specify known properties, and 'p4' does not exist in type '{ p1: "left"; p2: true; p3: number; } | { p1: "left"; p2: boolean; }'.
tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(57,5): error TS2322: Type '{ p1: "right"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
Expand Down Expand Up @@ -59,10 +59,10 @@ tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(136,5): err
p1: 'left',
p2: false,
p3: 42,
p4: "hello"
~~
!!! error TS2322: Type '{ p1: "left"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
!!! error TS2322: Object literal may only specify known properties, and 'p3' does not exist in type '{ p1: "left"; p2: boolean; }'.
p4: "hello"
!!! error TS2322: Object literal may only specify known properties, and 'p4' does not exist in type '{ p1: "left"; p2: true; p3: number; } | { p1: "left"; p2: boolean; }'.
};

// This has excess error because variant two is not applicable.
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10 changes: 4 additions & 6 deletions tests/baselines/reference/objectLiteralNormalization.errors.txt
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Expand Up @@ -5,9 +5,8 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(9,1): error TS2322: Type '{ c: true; }' is not assignable to type '{ a: number; b?: undefined; c?: undefined; } | { a: number; b: string; c?: undefined; } | { a: number; b: string; c: boolean; }'.
Type '{ c: true; }' is missing the following properties from type '{ a: number; b: string; c: boolean; }': a, b
tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(17,1): error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
Type '{ a: string; b: number; }' is not assignable to type '{ a?: undefined; b?: undefined; }'.
Types of property 'a' are incompatible.
Type 'string' is not assignable to type 'undefined'.
Types of property 'b' are incompatible.
Type 'number' is not assignable to type 'undefined'.
tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(18,1): error TS2322: Type '{ a: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
Property 'b' is missing in type '{ a: number; }' but required in type '{ a: number; b: number; }'.
tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(48,20): error TS2322: Type '2' is not assignable to type '1'.
Expand Down Expand Up @@ -44,9 +43,8 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
a2 = { a: "def", b: 20 }; // Error
~~
!!! error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
!!! error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a?: undefined; b?: undefined; }'.
!!! error TS2322: Types of property 'a' are incompatible.
!!! error TS2322: Type 'string' is not assignable to type 'undefined'.
!!! error TS2322: Types of property 'b' are incompatible.
!!! error TS2322: Type 'number' is not assignable to type 'undefined'.
a2 = { a: 1 }; // Error
~~
!!! error TS2322: Type '{ a: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
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9 changes: 9 additions & 0 deletions tests/cases/fourslash/completionsUnionStringLiteralProperty.ts
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@@ -0,0 +1,9 @@
/// <reference path="fourslash.ts" />

//// type Foo = { a: 0, b: 'x' } | { a: 0, b: 'y' } | { a: 1, b: 'z' };
//// const foo: Foo = { a: 0, b: '/*1*/' }
////
//// type Bar = { a: 0, b: 'fx' } | { a: 0, b: 'fy' } | { a: 1, b: 'fz' };
//// const bar: Bar = { a: 0, b: 'f/*2*/' }
verify.completions({ marker: "1", triggerCharacter: "'", includes: [ "x", "y" ], excludes: [ "z" ] });
verify.completions({ marker: "2", triggerCharacter: "'", includes: [ "fx", "fy" ], excludes: [ "fz" ] });