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Consistently error when rest element isn't last in tuple type #40254

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merged 7 commits into from
Sep 8, 2020
Merged

Consistently error when rest element isn't last in tuple type #40254

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83a873d
Consistently error when rest element isn't last in tuple type
ahejlsberg Aug 25, 2020
fa46b60
Add regression test
ahejlsberg Aug 25, 2020
355706d
Accept new baselines
ahejlsberg Aug 25, 2020
80e6df6
Stricter circular recursion check in type inference
ahejlsberg Aug 25, 2020
0ca4e48
Revert "Stricter circular recursion check in type inference"
ahejlsberg Aug 26, 2020
1ba3cc3
Revert "Accept new baselines"
ahejlsberg Aug 26, 2020
13e80d8
Accept new baselines
ahejlsberg Aug 26, 2020
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16 changes: 11 additions & 5 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -31121,6 +31121,7 @@ namespace ts {
function checkTupleType(node: TupleTypeNode) {
const elementTypes = node.elements;
let seenOptionalElement = false;
let seenRestElement = false;
const hasNamedElement = some(elementTypes, isNamedTupleMember);
for (let i = 0; i < elementTypes.length; i++) {
const e = elementTypes[i];
Expand All @@ -31130,16 +31131,17 @@ namespace ts {
}
const flags = getTupleElementFlags(e);
if (flags & ElementFlags.Variadic) {
if (!isArrayLikeType(getTypeFromTypeNode((<RestTypeNode | NamedTupleMember>e).type))) {
const type = getTypeFromTypeNode((<RestTypeNode | NamedTupleMember>e).type);
if (!isArrayLikeType(type)) {
error(e, Diagnostics.A_rest_element_type_must_be_an_array_type);
break;
}
if (isArrayType(type) || isTupleType(type) && type.target.combinedFlags & ElementFlags.Rest) {
seenRestElement = true;
}
}
else if (flags & ElementFlags.Rest) {
if (i !== elementTypes.length - 1) {
grammarErrorOnNode(e, Diagnostics.A_rest_element_must_be_last_in_a_tuple_type);
break;
}
seenRestElement = true;
}
else if (flags & ElementFlags.Optional) {
seenOptionalElement = true;
Expand All @@ -31148,6 +31150,10 @@ namespace ts {
grammarErrorOnNode(e, Diagnostics.A_required_element_cannot_follow_an_optional_element);
break;
}
if (seenRestElement && i !== elementTypes.length - 1) {
grammarErrorOnNode(e, Diagnostics.A_rest_element_must_be_last_in_a_tuple_type);
break;
}
}
forEach(node.elements, checkSourceElement);
}
Expand Down
21 changes: 20 additions & 1 deletion tests/baselines/reference/variadicTuples1.errors.txt
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Expand Up @@ -41,9 +41,12 @@ tests/cases/conformance/types/tuple/variadicTuples1.ts(203,5): error TS2322: Typ
Type '"2"' is not assignable to type 'number | "0" | "length" | "toString" | "toLocaleString" | "pop" | "push" | "concat" | "join" | "reverse" | "shift" | "slice" | "sort" | "splice" | "unshift" | "indexOf" | "lastIndexOf" | "every" | "some" | "forEach" | "map" | "filter" | "reduce" | "reduceRight" | "1"'.
tests/cases/conformance/types/tuple/variadicTuples1.ts(346,14): error TS7019: Rest parameter 'x' implicitly has an 'any[]' type.
tests/cases/conformance/types/tuple/variadicTuples1.ts(354,26): error TS2322: Type 'string' is not assignable to type 'number | undefined'.
tests/cases/conformance/types/tuple/variadicTuples1.ts(393,19): error TS1256: A rest element must be last in a tuple type.
tests/cases/conformance/types/tuple/variadicTuples1.ts(396,20): error TS1256: A rest element must be last in a tuple type.
tests/cases/conformance/types/tuple/variadicTuples1.ts(397,12): error TS1256: A rest element must be last in a tuple type.


==== tests/cases/conformance/types/tuple/variadicTuples1.ts (20 errors) ====
==== tests/cases/conformance/types/tuple/variadicTuples1.ts (23 errors) ====
// Variadics in tuple types

type TV0<T extends unknown[]> = [string, ...T];
Expand Down Expand Up @@ -496,4 +499,20 @@ tests/cases/conformance/types/tuple/variadicTuples1.ts(354,26): error TS2322: Ty

callApi(getUser);
callApi(getOrgUser);

// Repro from #40235

type Numbers = number[];
type Unbounded = [...Numbers, boolean];
~~~~~~~~~~
!!! error TS1256: A rest element must be last in a tuple type.
const data: Unbounded = [false, false];

type U1 = [string, ...Numbers, boolean];
~~~~~~~~~~
!!! error TS1256: A rest element must be last in a tuple type.
type U2 = [...[string, ...Numbers], boolean];
~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS1256: A rest element must be last in a tuple type.
type U3 = [...[string, number], boolean];
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Not sure if I get this right, does this mean we still have (or bring back) the constraint that a rest element must be at last in a tuple?
In 4.0 doc, I can see the below update:

The second change is that rest elements can occur anywhere in a tuple - not just at the end!
Previously, TypeScript would issue an error like the following:
But with TypeScript 4.0, this restriction is relaxed.

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@ahejlsberg


17 changes: 17 additions & 0 deletions tests/baselines/reference/variadicTuples1.js
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Expand Up @@ -387,6 +387,16 @@ function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, ob

callApi(getUser);
callApi(getOrgUser);

// Repro from #40235

type Numbers = number[];
type Unbounded = [...Numbers, boolean];
const data: Unbounded = [false, false];

type U1 = [string, ...Numbers, boolean];
type U2 = [...[string, ...Numbers], boolean];
type U3 = [...[string, number], boolean];


//// [variadicTuples1.js]
Expand Down Expand Up @@ -609,6 +619,7 @@ function callApi(method) {
}
callApi(getUser);
callApi(getOrgUser);
var data = [false, false];


//// [variadicTuples1.d.ts]
Expand Down Expand Up @@ -774,3 +785,9 @@ declare function getOrgUser(id: string, orgId: number, options?: {
z?: boolean;
}): void;
declare function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U): (...args_0: T) => U;
declare type Numbers = number[];
declare type Unbounded = [...Numbers, boolean];
declare const data: Unbounded;
declare type U1 = [string, ...Numbers, boolean];
declare type U2 = [...[string, ...Numbers], boolean];
declare type U3 = [...[string, number], boolean];
24 changes: 24 additions & 0 deletions tests/baselines/reference/variadicTuples1.symbols
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Expand Up @@ -1327,3 +1327,27 @@ callApi(getOrgUser);
>callApi : Symbol(callApi, Decl(variadicTuples1.ts, 380, 100))
>getOrgUser : Symbol(getOrgUser, Decl(variadicTuples1.ts, 378, 71))

// Repro from #40235

type Numbers = number[];
>Numbers : Symbol(Numbers, Decl(variadicTuples1.ts, 387, 20))

type Unbounded = [...Numbers, boolean];
>Unbounded : Symbol(Unbounded, Decl(variadicTuples1.ts, 391, 24))
>Numbers : Symbol(Numbers, Decl(variadicTuples1.ts, 387, 20))

const data: Unbounded = [false, false];
>data : Symbol(data, Decl(variadicTuples1.ts, 393, 5))
>Unbounded : Symbol(Unbounded, Decl(variadicTuples1.ts, 391, 24))

type U1 = [string, ...Numbers, boolean];
>U1 : Symbol(U1, Decl(variadicTuples1.ts, 393, 39))
>Numbers : Symbol(Numbers, Decl(variadicTuples1.ts, 387, 20))

type U2 = [...[string, ...Numbers], boolean];
>U2 : Symbol(U2, Decl(variadicTuples1.ts, 395, 40))
>Numbers : Symbol(Numbers, Decl(variadicTuples1.ts, 387, 20))

type U3 = [...[string, number], boolean];
>U3 : Symbol(U3, Decl(variadicTuples1.ts, 396, 45))

23 changes: 23 additions & 0 deletions tests/baselines/reference/variadicTuples1.types
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Expand Up @@ -1383,3 +1383,26 @@ callApi(getOrgUser);
>callApi : <T extends unknown[] = [], U = void>(method: (...args_0: T, args_1: object) => U) => (...args_0: T) => U
>getOrgUser : (id: string, orgId: number, options?: { y?: number | undefined; z?: boolean | undefined; } | undefined) => void

// Repro from #40235

type Numbers = number[];
>Numbers : Numbers

type Unbounded = [...Numbers, boolean];
>Unbounded : (number | boolean)[]

const data: Unbounded = [false, false];
>data : (number | boolean)[]
>[false, false] : false[]
>false : false
>false : false

type U1 = [string, ...Numbers, boolean];
>U1 : [string, ...(number | boolean)[]]

type U2 = [...[string, ...Numbers], boolean];
>U2 : [string, ...(number | boolean)[]]

type U3 = [...[string, number], boolean];
>U3 : [string, number, boolean]

10 changes: 10 additions & 0 deletions tests/cases/conformance/types/tuple/variadicTuples1.ts
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Expand Up @@ -389,3 +389,13 @@ function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, ob

callApi(getUser);
callApi(getOrgUser);

// Repro from #40235

type Numbers = number[];
type Unbounded = [...Numbers, boolean];
const data: Unbounded = [false, false];

type U1 = [string, ...Numbers, boolean];
type U2 = [...[string, ...Numbers], boolean];
type U3 = [...[string, number], boolean];