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

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This commit is contained in:
Anders Hejlsberg
2020-08-25 13:19:42 -10:00
parent c5446d1a47
commit 83a873d9c7
1 changed files with 11 additions and 5 deletions
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16
src/compiler/checker.ts
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@@ -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];
@@ -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;
@@ -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);
}