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Allow rest elements to follow other rest elements in tuple types #55446

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Allow rest elements to follow other rest elements in tuple types #55446

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23 changes: 18 additions & 5 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -16307,14 +16307,31 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return false;
}

function isTupleNormalizable(node: TupleTypeNode) {
let hasSeenRest = false;
for (const element of node.elements) {
const flags = getTupleElementFlags(element);
if (flags & ElementFlags.Variadic) {
return true;
}
if (flags & ElementFlags.Rest) {
if (hasSeenRest) {
return true;
}
hasSeenRest = true;
}
}
return false;
}

function getTypeFromArrayOrTupleTypeNode(node: ArrayTypeNode | TupleTypeNode): Type {
const links = getNodeLinks(node);
if (!links.resolvedType) {
const target = getArrayOrTupleTargetType(node);
if (target === emptyGenericType) {
links.resolvedType = emptyObjectType;
}
else if (!(node.kind === SyntaxKind.TupleType && some(node.elements, e => !!(getTupleElementFlags(e) & ElementFlags.Variadic))) && isDeferredTypeReferenceNode(node)) {
else if (!(node.kind === SyntaxKind.TupleType && isTupleNormalizable(node)) && isDeferredTypeReferenceNode(node)) {
links.resolvedType = node.kind === SyntaxKind.TupleType && node.elements.length === 0 ? target :
createDeferredTypeReference(target, node, /*mapper*/ undefined);
}
Expand Down Expand Up @@ -39410,10 +39427,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
}
else if (flags & ElementFlags.Rest) {
if (seenRestElement) {
grammarErrorOnNode(e, Diagnostics.A_rest_element_cannot_follow_another_rest_element);
break;
}
seenRestElement = true;
}
else if (flags & ElementFlags.Optional) {
Expand Down
4 changes: 0 additions & 4 deletions src/compiler/diagnosticMessages.json
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Expand Up @@ -855,10 +855,6 @@
"category": "Error",
"code": 1264
},
"A rest element cannot follow another rest element.": {
"category": "Error",
"code": 1265
},
"An optional element cannot follow a rest element.": {
"category": "Error",
"code": 1266
Expand Down
11 changes: 4 additions & 7 deletions tests/baselines/reference/variadicTuples2.errors.txt
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@@ -1,4 +1,3 @@
variadicTuples2.ts(7,34): error TS1265: A rest element cannot follow another rest element.
variadicTuples2.ts(8,34): error TS1266: An optional element cannot follow a rest element.
variadicTuples2.ts(9,30): error TS1257: A required element cannot follow an optional element.
variadicTuples2.ts(42,1): error TS2322: Type '[string, string, number, number]' is not assignable to type '[...string[], number]'.
Expand Down Expand Up @@ -65,20 +64,18 @@ variadicTuples2.ts(134,25): error TS2345: Argument of type '["blah2", 1, 2, 3]'
Type 'number' is not assignable to type 'string'.


==== variadicTuples2.ts (29 errors) ====
==== variadicTuples2.ts (28 errors) ====
// Declarations

type V00 = [number, ...string[]];
type V01 = [...string[], number];
type V03 = [number, ...string[], number];
type V04 = [number, ...string[], ...boolean[]];

type V10 = [number, ...string[], ...boolean[]]; // Error
~~~~~~~~~~~~
!!! error TS1265: A rest element cannot follow another rest element.
type V11 = [number, ...string[], boolean?]; // Error
type V10 = [number, ...string[], boolean?]; // Error
~~~~~~~~
!!! error TS1266: An optional element cannot follow a rest element.
type V12 = [number, string?, boolean]; // Error
type V11 = [number, string?, boolean]; // Error
~~~~~~~
!!! error TS1257: A required element cannot follow an optional element.

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12 changes: 6 additions & 6 deletions tests/baselines/reference/variadicTuples2.js
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Expand Up @@ -6,10 +6,10 @@
type V00 = [number, ...string[]];
type V01 = [...string[], number];
type V03 = [number, ...string[], number];
type V04 = [number, ...string[], ...boolean[]];

type V10 = [number, ...string[], ...boolean[]]; // Error
type V11 = [number, ...string[], boolean?]; // Error
type V12 = [number, string?, boolean]; // Error
type V10 = [number, ...string[], boolean?]; // Error
type V11 = [number, string?, boolean]; // Error

// Normalization

Expand Down Expand Up @@ -239,9 +239,9 @@ var e1 = foo('blah1', 'blah2', 1, 2, 3); // Error
type V00 = [number, ...string[]];
type V01 = [...string[], number];
type V03 = [number, ...string[], number];
type V10 = [number, ...string[], ...boolean[]];
type V11 = [number, ...string[], boolean?];
type V12 = [number, string?, boolean];
type V04 = [number, ...string[], ...boolean[]];
type V10 = [number, ...string[], boolean?];
type V11 = [number, string?, boolean];
type Tup3<T extends unknown[], U extends unknown[], V extends unknown[]> = [...T, ...U, ...V];
type V20 = Tup3<[number], string[], [number]>;
type V21 = Tup3<[number], [string?], [boolean]>;
Expand Down
12 changes: 6 additions & 6 deletions tests/baselines/reference/variadicTuples2.symbols
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Expand Up @@ -12,14 +12,14 @@ type V01 = [...string[], number];
type V03 = [number, ...string[], number];
>V03 : Symbol(V03, Decl(variadicTuples2.ts, 3, 33))

type V10 = [number, ...string[], ...boolean[]]; // Error
>V10 : Symbol(V10, Decl(variadicTuples2.ts, 4, 41))
type V04 = [number, ...string[], ...boolean[]];
>V04 : Symbol(V04, Decl(variadicTuples2.ts, 4, 41))

type V11 = [number, ...string[], boolean?]; // Error
>V11 : Symbol(V11, Decl(variadicTuples2.ts, 6, 47))
type V10 = [number, ...string[], boolean?]; // Error
>V10 : Symbol(V10, Decl(variadicTuples2.ts, 5, 47))

type V12 = [number, string?, boolean]; // Error
>V12 : Symbol(V12, Decl(variadicTuples2.ts, 7, 43))
type V11 = [number, string?, boolean]; // Error
>V11 : Symbol(V11, Decl(variadicTuples2.ts, 7, 43))

// Normalization

Expand Down
12 changes: 6 additions & 6 deletions tests/baselines/reference/variadicTuples2.types
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Expand Up @@ -12,14 +12,14 @@ type V01 = [...string[], number];
type V03 = [number, ...string[], number];
>V03 : [number, ...string[], number]

type V10 = [number, ...string[], ...boolean[]]; // Error
>V10 : [number, ...string[], ...boolean[]]
type V04 = [number, ...string[], ...boolean[]];
>V04 : [number, ...(string | boolean)[]]

type V11 = [number, ...string[], boolean?]; // Error
>V11 : [number, ...string[], (boolean | undefined)?]
type V10 = [number, ...string[], boolean?]; // Error
>V10 : [number, ...string[], (boolean | undefined)?]

type V12 = [number, string?, boolean]; // Error
>V12 : [number, (string | undefined)?, boolean]
type V11 = [number, string?, boolean]; // Error
>V11 : [number, (string | undefined)?, boolean]

// Normalization

Expand Down
6 changes: 3 additions & 3 deletions tests/cases/conformance/types/tuple/variadicTuples2.ts
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Expand Up @@ -6,10 +6,10 @@
type V00 = [number, ...string[]];
type V01 = [...string[], number];
type V03 = [number, ...string[], number];
type V04 = [number, ...string[], ...boolean[]];

type V10 = [number, ...string[], ...boolean[]]; // Error
type V11 = [number, ...string[], boolean?]; // Error
type V12 = [number, string?, boolean]; // Error
type V10 = [number, ...string[], boolean?]; // Error
type V11 = [number, string?, boolean]; // Error

// Normalization

Expand Down